1
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Carr CR, Crawford KHD, Murphy M, Galloway JG, Haddox HK, Matsen FA, Andersen KG, King NP, Bloom JD. Deep mutational scanning reveals functional constraints and antibody-escape potential of Lassa virus glycoprotein complex. Immunity 2024; 57:2061-2076.e11. [PMID: 39013466 PMCID: PMC11390330 DOI: 10.1016/j.immuni.2024.06.013] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2024] [Revised: 04/23/2024] [Accepted: 06/20/2024] [Indexed: 07/18/2024]
Abstract
Lassa virus is estimated to cause thousands of human deaths per year, primarily due to spillovers from its natural host, Mastomys rodents. Efforts to create vaccines and antibody therapeutics must account for the evolutionary variability of the Lassa virus's glycoprotein complex (GPC), which mediates viral entry into cells and is the target of neutralizing antibodies. To map the evolutionary space accessible to GPC, we used pseudovirus deep mutational scanning to measure how nearly all GPC amino-acid mutations affected cell entry and antibody neutralization. Our experiments defined functional constraints throughout GPC. We quantified how GPC mutations affected neutralization with a panel of monoclonal antibodies. All antibodies tested were escaped by mutations that existed among natural Lassa virus lineages. Overall, our work describes a biosafety-level-2 method to elucidate the mutational space accessible to GPC and shows how prospective characterization of antigenic variation could aid the design of therapeutics and vaccines.
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Affiliation(s)
- Caleb R Carr
- Basic Sciences Division and Computational Biology Program, Fred Hutchinson Cancer Center, Seattle, WA 98109, USA; Department of Genome Sciences, University of Washington, Seattle, WA 98195, USA; Medical Scientist Training Program, University of Washington, Seattle, WA 98195, USA
| | - Katharine H D Crawford
- Basic Sciences Division and Computational Biology Program, Fred Hutchinson Cancer Center, Seattle, WA 98109, USA; Department of Genome Sciences, University of Washington, Seattle, WA 98195, USA; Medical Scientist Training Program, University of Washington, Seattle, WA 98195, USA
| | - Michael Murphy
- Department of Biochemistry, University of Washington, Seattle, WA 98195, USA; Institute for Protein Design, University of Washington, Seattle, WA 98195, USA
| | - Jared G Galloway
- Basic Sciences Division and Computational Biology Program, Fred Hutchinson Cancer Center, Seattle, WA 98109, USA
| | - Hugh K Haddox
- Basic Sciences Division and Computational Biology Program, Fred Hutchinson Cancer Center, Seattle, WA 98109, USA
| | - Frederick A Matsen
- Basic Sciences Division and Computational Biology Program, Fred Hutchinson Cancer Center, Seattle, WA 98109, USA; Department of Statistics, University of Washington, Seattle, WA 98195, USA; Howard Hughes Medical Institute, Seattle, WA 98109, USA
| | - Kristian G Andersen
- Department of Immunology and Microbiology, The Scripps Research Institute, La Jolla, CA 92037, USA; Scripps Research Translational Institute, La Jolla, CA 92037, USA
| | - Neil P King
- Department of Biochemistry, University of Washington, Seattle, WA 98195, USA; Institute for Protein Design, University of Washington, Seattle, WA 98195, USA
| | - Jesse D Bloom
- Basic Sciences Division and Computational Biology Program, Fred Hutchinson Cancer Center, Seattle, WA 98109, USA; Department of Genome Sciences, University of Washington, Seattle, WA 98195, USA; Howard Hughes Medical Institute, Seattle, WA 98109, USA.
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2
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Walton RT, Qin Y, Blainey PC. CROPseq-multi: a versatile solution for multiplexed perturbation and decoding in pooled CRISPR screens. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.03.17.585235. [PMID: 38558968 PMCID: PMC10979941 DOI: 10.1101/2024.03.17.585235] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 04/04/2024]
Abstract
Forward genetic screens seek to dissect complex biological systems by systematically perturbing genetic elements and observing the resulting phenotypes. While standard screening methodologies introduce individual perturbations, multiplexing perturbations improves the performance of single-target screens and enables combinatorial screens for the study of genetic interactions. Current tools for multiplexing perturbations are incompatible with pooled screening methodologies that require mRNA-embedded barcodes, including some microscopy and single cell sequencing approaches. Here, we report the development of CROPseq-multi, a CROPseq1-inspired lentiviral system to multiplex Streptococcus pyogenes (Sp) Cas9-based perturbations with mRNA-embedded barcodes. CROPseq-multi has equivalent per-guide activity to CROPseq and low lentiviral recombination frequencies. CROPseq-multi is compatible with enrichment screening methodologies and optical pooled screens, and is extensible to screens with single-cell sequencing readouts. For optical pooled screens, an optimized and multiplexed in situ detection protocol improves barcode detection efficiency 10-fold, enables detection of recombination events, and increases decoding efficiency 3-fold relative to CROPseq. CROPseq-multi is a widely applicable multiplexing solution for diverse SpCas9-based genetic screening approaches.
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Affiliation(s)
- Russell T. Walton
- Broad Institute of MIT and Harvard, Cambridge, MA, USA
- Department of Biological Engineering, MIT, Cambridge, MA, USA
| | - Yue Qin
- Broad Institute of MIT and Harvard, Cambridge, MA, USA
- Eric and Wendy Schmidt Center, Broad Institute of MIT and Harvard, Cambridge, MA, USA
| | - Paul C. Blainey
- Broad Institute of MIT and Harvard, Cambridge, MA, USA
- Department of Biological Engineering, MIT, Cambridge, MA, USA
- Koch Institute for Integrative Cancer Research, MIT, Cambridge, MA, USA
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3
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Carr CR, Crawford KHD, Murphy M, Galloway JG, Haddox HK, Matsen FA, Andersen KG, King NP, Bloom JD. Deep mutational scanning reveals functional constraints and antigenic variability of Lassa virus glycoprotein complex. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.02.05.579020. [PMID: 38370709 PMCID: PMC10871245 DOI: 10.1101/2024.02.05.579020] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/20/2024]
Abstract
Lassa virus is estimated to cause thousands of human deaths per year, primarily due to spillovers from its natural host, Mastomys rodents. Efforts to create vaccines and antibody therapeutics must account for the evolutionary variability of Lassa virus's glycoprotein complex (GPC), which mediates viral entry into cells and is the target of neutralizing antibodies. To map the evolutionary space accessible to GPC, we use pseudovirus deep mutational scanning to measure how nearly all GPC amino-acid mutations affect cell entry and antibody neutralization. Our experiments define functional constraints throughout GPC. We quantify how GPC mutations affect neutralization by a panel of monoclonal antibodies and show that all antibodies are escaped by mutations that exist among natural Lassa virus lineages. Overall, our work describes a biosafety-level-2 method to elucidate the mutational space accessible to GPC and shows how prospective characterization of antigenic variation could aid design of therapeutics and vaccines.
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Affiliation(s)
- Caleb R. Carr
- Basic Sciences Division and Computational Biology Program, Fred Hutchinson Cancer Center, Seattle, WA 98109, USA
- Department of Genome Sciences, University of Washington, Seattle, WA 98109, USA
- Medical Scientist Training Program, University of Washington, Seattle, WA 98109, USA
| | - Katharine H. D. Crawford
- Basic Sciences Division and Computational Biology Program, Fred Hutchinson Cancer Center, Seattle, WA 98109, USA
- Department of Genome Sciences, University of Washington, Seattle, WA 98109, USA
- Medical Scientist Training Program, University of Washington, Seattle, WA 98109, USA
| | - Michael Murphy
- Department of Biochemistry, University of Washington, Seattle, WA 98195, USA
- Institute for Protein Design, University of Washington, Seattle, WA 98195, USA
| | - Jared G. Galloway
- Basic Sciences Division and Computational Biology Program, Fred Hutchinson Cancer Center, Seattle, WA 98109, USA
| | - Hugh K. Haddox
- Basic Sciences Division and Computational Biology Program, Fred Hutchinson Cancer Center, Seattle, WA 98109, USA
| | - Frederick A. Matsen
- Basic Sciences Division and Computational Biology Program, Fred Hutchinson Cancer Center, Seattle, WA 98109, USA
- Department of Statistics, University of Washington, Seattle, WA 98195, USA
- Howard Hughes Medical Institute, Seattle, WA 98109, USA
| | - Kristian G. Andersen
- Department of Immunology and Microbiology, The Scripps Research Institute, La Jolla, CA 92037, USA
- Scripps Research Translational Institute, La Jolla, CA 92037, USA
| | - Neil P. King
- Department of Biochemistry, University of Washington, Seattle, WA 98195, USA
- Institute for Protein Design, University of Washington, Seattle, WA 98195, USA
| | - Jesse D. Bloom
- Basic Sciences Division and Computational Biology Program, Fred Hutchinson Cancer Center, Seattle, WA 98109, USA
- Department of Genome Sciences, University of Washington, Seattle, WA 98109, USA
- Howard Hughes Medical Institute, Seattle, WA 98109, USA
- Lead contact
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4
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Romero EV, Feder AF. Elevated HIV Viral Load is Associated with Higher Recombination Rate In Vivo. Mol Biol Evol 2024; 41:msad260. [PMID: 38197289 PMCID: PMC10777272 DOI: 10.1093/molbev/msad260] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2023] [Revised: 11/21/2023] [Accepted: 11/27/2023] [Indexed: 01/11/2024] Open
Abstract
HIV's exceptionally high recombination rate drives its intrahost diversification, enabling immune escape and multidrug resistance within people living with HIV. While we know that HIV's recombination rate varies by genomic position, we have little understanding of how recombination varies throughout infection or between individuals as a function of the rate of cellular coinfection. We hypothesize that denser intrahost populations may have higher rates of coinfection and therefore recombination. To test this hypothesis, we develop a new approach (recombination analysis via time series linkage decay or RATS-LD) to quantify recombination using autocorrelation of linkage between mutations across time points. We validate RATS-LD on simulated data under short read sequencing conditions and then apply it to longitudinal, high-throughput intrahost viral sequencing data, stratifying populations by viral load (a proxy for density). Among sampled viral populations with the lowest viral loads (<26,800 copies/mL), we estimate a recombination rate of 1.5×10-5 events/bp/generation (95% CI: 7×10-6 to 2.9×10-5), similar to existing estimates. However, among samples with the highest viral loads (>82,000 copies/mL), our median estimate is approximately 6 times higher. In addition to co-varying across individuals, we also find that recombination rate and viral load are associated within single individuals across different time points. Our findings suggest that rather than acting as a constant, uniform force, recombination can vary dynamically and drastically across intrahost viral populations and within them over time. More broadly, we hypothesize that this phenomenon may affect other facultatively asexual populations where spatial co-localization varies.
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Affiliation(s)
- Elena V Romero
- Department of Genome Sciences, University of Washington, Seattle, WA, USA
| | - Alison F Feder
- Department of Genome Sciences, University of Washington, Seattle, WA, USA
- Herbold Computational Biology Program, Fred Hutchinson Cancer Center, Seattle, WA, USA
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5
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Romero EV, Feder AF. Elevated HIV viral load is associated with higher recombination rate in vivo. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.05.05.539643. [PMID: 37873119 PMCID: PMC10592651 DOI: 10.1101/2023.05.05.539643] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/25/2023]
Abstract
HIV's exceptionally high recombination rate drives its intra-host diversification, enabling immune escape and multi-drug resistance within people living with HIV. While we know that HIV's recombination rate varies by genomic position, we have little understanding of how recombination varies throughout infection or between individuals as a function of the rate of cellular coinfection. We hypothesize that denser intra-host populations may have higher rates of coinfection and therefore recombination. To test this hypothesis, we develop a new approach (Recombination Analysis via Time Series Linkage Decay, or RATS-LD) to quantify recombination using autocorrelation of linkage between mutations across time points. We validate RATS-LD on simulated data under short read sequencing conditions and then apply it to longitudinal, high-throughput intra-host viral sequencing data, stratifying populations by viral load (a proxy for density). Among sampled viral populations with the lowest viral loads (< 26,800 copies/mL), we estimate a recombination rate of 1.5 × 10-5 events/bp/generation (95% CI: 7 × 10-6 - 2.9 × 10-5), similar to existing estimates. However, among samples with the highest viral loads (> 82,000 copies/mL), our median estimate is approximately 6 times higher. In addition to co-varying across individuals, we also find that recombination rate and viral load are associated within single individuals across different time points. Our findings suggest that rather than acting as a constant, uniform force, recombination can vary dynamically and drastically across intra-host viral populations and within them over time. More broadly, we hypothesize that this phenomenon may affect other facultatively asexual populations where spatial co-localization varies.
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Affiliation(s)
- Elena V. Romero
- Department of Genome Sciences, University of Washington, Seattle, WA, USA
| | - Alison F. Feder
- Department of Genome Sciences, University of Washington, Seattle, WA, USA
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6
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Carr A, Mackie NE, Paredes R, Ruxrungtham K. HIV drug resistance in the era of contemporary antiretroviral therapy: A clinical perspective. Antivir Ther 2023; 28:13596535231201162. [PMID: 37749751 DOI: 10.1177/13596535231201162] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 09/27/2023]
Abstract
Contemporary antiretroviral therapy (ART) regimens have high barriers to the development of drug resistance. However, resistance to earlier antiretrovirals and uncommon cases of resistance to contemporary ART illustrate the continued need for good clinical management of HIV drug resistance. Here, we describe HIV drug-resistance mechanisms, the interaction of HIV drug-resistant mutations and the patterns of drug resistance to contemporary ART. We then provide guidance on the management of HIV drug resistance, including how to limit the development of resistance and manage virologic failure that is complicated by resistance. To complement this, links to resources and treatment guidelines are provided that can assist with the interpretation of HIV drug resistance test results and optimal ART selection in the clinic.
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Affiliation(s)
- Andrew Carr
- HIV and Immunology Unit, St Vincent's Hospital, Sydney, NSW, Australia
- University of New South Wales, Sydney, NSW, Australia
| | | | - Roger Paredes
- Department of Infectious Diseases, Hospital Germans Trias i Pujol, Barcelona, Spain
- IrsiCaixa AIDS Research Institute, Barcelona, Spain
| | - Kiat Ruxrungtham
- Chula Vaccine Research Center (Chula VRC), Faculty of Medicine, Chulalongkorn University, Bangkok, Thailand
- School of Global Health, Faculty of Medicine, Chulalongkorn University, Bangkok, Thailand
- The HIV Netherlands Australia Thailand Research Collaboration (HIV-NAT), Thai Red Cross AIDS Research Centre, Bangkok, Thailand
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7
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Radford CE, Schommers P, Gieselmann L, Crawford KHD, Dadonaite B, Yu TC, Dingens AS, Overbaugh J, Klein F, Bloom JD. Mapping the neutralizing specificity of human anti-HIV serum by deep mutational scanning. Cell Host Microbe 2023; 31:1200-1215.e9. [PMID: 37327779 PMCID: PMC10351223 DOI: 10.1016/j.chom.2023.05.025] [Citation(s) in RCA: 11] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2023] [Revised: 05/15/2023] [Accepted: 05/23/2023] [Indexed: 06/18/2023]
Abstract
Understanding the specificities of human serum antibodies that broadly neutralize HIV can inform prevention and treatment strategies. Here, we describe a deep mutational scanning system that can measure the effects of combinations of mutations to HIV envelope (Env) on neutralization by antibodies and polyclonal serum. We first show that this system can accurately map how all functionally tolerated mutations to Env affect neutralization by monoclonal antibodies. We then comprehensively map Env mutations that affect neutralization by a set of human polyclonal sera that neutralize diverse strains of HIV and target the site engaging the host receptor CD4. The neutralizing activities of these sera target different epitopes, with most sera having specificities reminiscent of individual characterized monoclonal antibodies, but one serum targeting two epitopes within the CD4-binding site. Mapping the specificity of the neutralizing activity in polyclonal human serum will aid in assessing anti-HIV immune responses to inform prevention strategies.
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Affiliation(s)
- Caelan E Radford
- Molecular and Cellular Biology Graduate Program, University of Washington and Basic Sciences Division, Fred Hutch Cancer Center, Seattle, WA 98109, USA; Basic Sciences Division and Computational Biology Program, Fred Hutchinson Cancer Center, Seattle, WA 98109, USA
| | - Philipp Schommers
- Laboratory of Experimental Immunology, Institute of Virology, Faculty of Medicine and University Hospital of Cologne, University of Cologne, 50931 Cologne, Germany; German Center for Infection Research, partner site Bonn-Cologne, 50931 Cologne, Germany; Department I of Internal Medicine, Faculty of Medicine and University Hospital of Cologne, University of Cologne, 50931 Cologne, Germany
| | - Lutz Gieselmann
- Laboratory of Experimental Immunology, Institute of Virology, Faculty of Medicine and University Hospital of Cologne, University of Cologne, 50931 Cologne, Germany; German Center for Infection Research, partner site Bonn-Cologne, 50931 Cologne, Germany; Department I of Internal Medicine, Faculty of Medicine and University Hospital of Cologne, University of Cologne, 50931 Cologne, Germany
| | - Katharine H D Crawford
- Basic Sciences Division and Computational Biology Program, Fred Hutchinson Cancer Center, Seattle, WA 98109, USA; Department of Genome Sciences & Medical Scientist Training Program, University of Washington, Seattle, WA 98109, USA
| | - Bernadeta Dadonaite
- Basic Sciences Division and Computational Biology Program, Fred Hutchinson Cancer Center, Seattle, WA 98109, USA
| | - Timothy C Yu
- Molecular and Cellular Biology Graduate Program, University of Washington and Basic Sciences Division, Fred Hutch Cancer Center, Seattle, WA 98109, USA; Basic Sciences Division and Computational Biology Program, Fred Hutchinson Cancer Center, Seattle, WA 98109, USA
| | - Adam S Dingens
- Basic Sciences Division and Computational Biology Program, Fred Hutchinson Cancer Center, Seattle, WA 98109, USA
| | - Julie Overbaugh
- Division of Human Biology, Fred Hutchinson Cancer Center, Seattle, WA 98109, USA
| | - Florian Klein
- Laboratory of Experimental Immunology, Institute of Virology, Faculty of Medicine and University Hospital of Cologne, University of Cologne, 50931 Cologne, Germany; German Center for Infection Research, partner site Bonn-Cologne, 50931 Cologne, Germany; Department I of Internal Medicine, Faculty of Medicine and University Hospital of Cologne, University of Cologne, 50931 Cologne, Germany
| | - Jesse D Bloom
- Basic Sciences Division and Computational Biology Program, Fred Hutchinson Cancer Center, Seattle, WA 98109, USA; Howard Hughes Medical Institute, Seattle, WA 98109, USA.
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8
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Seo SY, Min S, Lee S, Seo JH, Park J, Kim HK, Song M, Baek D, Cho SR, Kim HH. Massively parallel evaluation and computational prediction of the activities and specificities of 17 small Cas9s. Nat Methods 2023:10.1038/s41592-023-01875-2. [PMID: 37188955 DOI: 10.1038/s41592-023-01875-2] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2022] [Accepted: 04/10/2023] [Indexed: 05/17/2023]
Abstract
Recently, various small Cas9 orthologs and variants have been reported for use in in vivo delivery applications. Although small Cas9s are particularly suited for this purpose, selecting the most optimal small Cas9 for use at a specific target sequence continues to be challenging. Here, to this end, we have systematically compared the activities of 17 small Cas9s for thousands of target sequences. For each small Cas9, we have characterized the protospacer adjacent motif and determined optimal single guide RNA expression formats and scaffold sequence. High-throughput comparative analyses revealed distinct high- and low-activity groups of small Cas9s. We also developed DeepSmallCas9, a set of computational models predicting the activities of the small Cas9s at matched and mismatched target sequences. Together, this analysis and these computational models provide a useful guide for researchers to select the most suitable small Cas9 for specific applications.
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Affiliation(s)
- Sang-Yeon Seo
- Department of Pharmacology, Yonsei University College of Medicine, Seoul, Republic of Korea
- Graduate School of Medical Science, Brain Korea 21 Project, Yonsei University College of Medicine, Seoul, Republic of Korea
| | | | - Sungtae Lee
- Department of Pharmacology, Yonsei University College of Medicine, Seoul, Republic of Korea
| | - Jung Hwa Seo
- Graduate School of Medical Science, Brain Korea 21 Project, Yonsei University College of Medicine, Seoul, Republic of Korea
- Department and Research Institute of Rehabilitation Medicine, Yonsei University College of Medicine, Seoul, Republic of Korea
| | - Jinman Park
- Department of Pharmacology, Yonsei University College of Medicine, Seoul, Republic of Korea
- Graduate School of Medical Science, Brain Korea 21 Project, Yonsei University College of Medicine, Seoul, Republic of Korea
| | - Hui Kwon Kim
- Department of Pharmacology, Yonsei University College of Medicine, Seoul, Republic of Korea
- Graduate School of Medical Science, Brain Korea 21 Project, Yonsei University College of Medicine, Seoul, Republic of Korea
- Center for Nanomedicine, Institute for Basic Science (IBS), Seoul, Republic of Korea
- Graduate Program of Nano Biomedical Engineering (NanoBME), Advanced Science Institute, Yonsei University, Seoul, Republic of Korea
- Department of Integrative Biotechnology, Sungkyunkwan University, Suwon, Republic of Korea
| | - Myungjae Song
- Department of Pharmacology, Yonsei University College of Medicine, Seoul, Republic of Korea
- Graduate School of Medical Science, Brain Korea 21 Project, Yonsei University College of Medicine, Seoul, Republic of Korea
| | - Dawoon Baek
- Department and Research Institute of Rehabilitation Medicine, Yonsei University College of Medicine, Seoul, Republic of Korea
- Department of Rehabilitation Medicine, Yonsei University Wonju College of Medicine, Wonju, Republic of Korea
| | - Sung-Rae Cho
- Graduate School of Medical Science, Brain Korea 21 Project, Yonsei University College of Medicine, Seoul, Republic of Korea
- Department and Research Institute of Rehabilitation Medicine, Yonsei University College of Medicine, Seoul, Republic of Korea
- Graduate Program of Biomedical Engineering, Yonsei University College of Medicine, Seoul, Republic of Korea
| | - Hyongbum Henry Kim
- Department of Pharmacology, Yonsei University College of Medicine, Seoul, Republic of Korea.
- Graduate School of Medical Science, Brain Korea 21 Project, Yonsei University College of Medicine, Seoul, Republic of Korea.
- Center for Nanomedicine, Institute for Basic Science (IBS), Seoul, Republic of Korea.
- Graduate Program of Nano Biomedical Engineering (NanoBME), Advanced Science Institute, Yonsei University, Seoul, Republic of Korea.
- Severance Biomedical Science Institute, Yonsei University College of Medicine, Seoul, Republic of Korea.
- Institute for Immunology and Immunological Diseases, Yonsei University College of Medicine, Seoul, Republic of Korea.
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9
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Radford CE, Schommers P, Gieselmann L, Crawford KHD, Dadonaite B, Yu TC, Dingens AS, Overbaugh J, Klein F, Bloom JD. Mapping the neutralizing specificity of human anti-HIV serum by deep mutational scanning. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.03.23.533993. [PMID: 36993197 PMCID: PMC10055425 DOI: 10.1101/2023.03.23.533993] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/19/2023]
Abstract
Understanding the specificities of human serum antibodies that broadly neutralize HIV can inform prevention and treatment strategies. Here we describe a deep mutational scanning system that can measure the effects of combinations of mutations to HIV envelope (Env) on neutralization by antibodies and polyclonal serum. We first show that this system can accurately map how all functionally tolerated mutations to Env affect neutralization by monoclonal antibodies. We then comprehensively map Env mutations that affect neutralization by a set of human polyclonal sera known to target the CD4-binding site that neutralize diverse strains of HIV. The neutralizing activities of these sera target different epitopes, with most sera having specificities reminiscent of individual characterized monoclonal antibodies, but one sera targeting two epitopes within the CD4 binding site. Mapping the specificity of the neutralizing activity in polyclonal human serum will aid in assessing anti-HIV immune responses to inform prevention strategies.
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Affiliation(s)
- Caelan E. Radford
- Molecular and Cellular Biology Graduate Program, University of
Washington, and Basic Sciences Division, Fred Hutch Cancer Center, Seattle, Washington,
98109, USA
- Basic Sciences Division and Computational Biology Program, Fred
Hutchinson Cancer Center, Seattle, Washington, 98109, USA
| | - Philipp Schommers
- Laboratory of Experimental Immunology, Institute of Virology,
Faculty of Medicine and University Hospital of Cologne, University of Cologne, 50931
Cologne, Germany
- German Center for Infection Research, partner site
Bonn–Cologne, 50931 Cologne, Germany
- Department I of Internal Medicine, Faculty of Medicine and
University Hospital of Cologne, University of Cologne, 50931 Cologne, Germany
| | - Lutz Gieselmann
- Laboratory of Experimental Immunology, Institute of Virology,
Faculty of Medicine and University Hospital of Cologne, University of Cologne, 50931
Cologne, Germany
- German Center for Infection Research, partner site
Bonn–Cologne, 50931 Cologne, Germany
- Department I of Internal Medicine, Faculty of Medicine and
University Hospital of Cologne, University of Cologne, 50931 Cologne, Germany
| | - Katharine H. D. Crawford
- Basic Sciences Division and Computational Biology Program, Fred
Hutchinson Cancer Center, Seattle, Washington, 98109, USA
- Department of Genome Sciences & Medical Scientist Training
Program, University of Washington, Seattle, Washington, 98109, USA
| | - Bernadeta Dadonaite
- Basic Sciences Division and Computational Biology Program, Fred
Hutchinson Cancer Center, Seattle, Washington, 98109, USA
| | - Timothy C. Yu
- Molecular and Cellular Biology Graduate Program, University of
Washington, and Basic Sciences Division, Fred Hutch Cancer Center, Seattle, Washington,
98109, USA
- Basic Sciences Division and Computational Biology Program, Fred
Hutchinson Cancer Center, Seattle, Washington, 98109, USA
| | - Adam S. Dingens
- Basic Sciences Division and Computational Biology Program, Fred
Hutchinson Cancer Center, Seattle, Washington, 98109, USA
| | - Julie Overbaugh
- Division of Human Biology, Fred Hutchinson Cancer Center,
Seattle, Washington, 98109, USA
| | - Florian Klein
- Laboratory of Experimental Immunology, Institute of Virology,
Faculty of Medicine and University Hospital of Cologne, University of Cologne, 50931
Cologne, Germany
- German Center for Infection Research, partner site
Bonn–Cologne, 50931 Cologne, Germany
- Department I of Internal Medicine, Faculty of Medicine and
University Hospital of Cologne, University of Cologne, 50931 Cologne, Germany
| | - Jesse D. Bloom
- Basic Sciences Division and Computational Biology Program, Fred
Hutchinson Cancer Center, Seattle, Washington, 98109, USA
- Howard Hughes Medical Institute, Seattle, WA, 98109, USA
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10
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Dadonaite B, Crawford KHD, Radford CE, Farrell AG, Yu TC, Hannon WW, Zhou P, Andrabi R, Burton DR, Liu L, Ho DD, Chu HY, Neher RA, Bloom JD. A pseudovirus system enables deep mutational scanning of the full SARS-CoV-2 spike. Cell 2023; 186:1263-1278.e20. [PMID: 36868218 PMCID: PMC9922669 DOI: 10.1016/j.cell.2023.02.001] [Citation(s) in RCA: 61] [Impact Index Per Article: 61.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2022] [Revised: 01/11/2023] [Accepted: 01/31/2023] [Indexed: 02/15/2023]
Abstract
A major challenge in understanding SARS-CoV-2 evolution is interpreting the antigenic and functional effects of emerging mutations in the viral spike protein. Here, we describe a deep mutational scanning platform based on non-replicative pseudotyped lentiviruses that directly quantifies how large numbers of spike mutations impact antibody neutralization and pseudovirus infection. We apply this platform to produce libraries of the Omicron BA.1 and Delta spikes. These libraries each contain ∼7,000 distinct amino acid mutations in the context of up to ∼135,000 unique mutation combinations. We use these libraries to map escape mutations from neutralizing antibodies targeting the receptor-binding domain, N-terminal domain, and S2 subunit of spike. Overall, this work establishes a high-throughput and safe approach to measure how ∼105 combinations of mutations affect antibody neutralization and spike-mediated infection. Notably, the platform described here can be extended to the entry proteins of many other viruses.
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Affiliation(s)
- Bernadeta Dadonaite
- Basic Sciences Division and Computational Biology Program, Fred Hutchinson Cancer Center, Seattle, WA 98109, USA
| | - Katharine H D Crawford
- Basic Sciences Division and Computational Biology Program, Fred Hutchinson Cancer Center, Seattle, WA 98109, USA; Department of Genome Sciences & Medical Scientist Training Program, University of Washington, Seattle, WA 98109, USA
| | - Caelan E Radford
- Basic Sciences Division and Computational Biology Program, Fred Hutchinson Cancer Center, Seattle, WA 98109, USA; Molecular and Cellular Biology Graduate Program, University of Washington, Seattle, WA 98109, USA
| | - Ariana G Farrell
- Basic Sciences Division and Computational Biology Program, Fred Hutchinson Cancer Center, Seattle, WA 98109, USA
| | - Timothy C Yu
- Basic Sciences Division and Computational Biology Program, Fred Hutchinson Cancer Center, Seattle, WA 98109, USA; Molecular and Cellular Biology Graduate Program, University of Washington, Seattle, WA 98109, USA
| | - William W Hannon
- Basic Sciences Division and Computational Biology Program, Fred Hutchinson Cancer Center, Seattle, WA 98109, USA; Molecular and Cellular Biology Graduate Program, University of Washington, Seattle, WA 98109, USA
| | - Panpan Zhou
- Department of Immunology and Microbiology, The Scripps Research Institute, La Jolla, CA 92037, USA; IAVI Neutralizing Antibody Center, The Scripps Research Institute, La Jolla, CA 92037, USA; Consortium for HIV/AIDS Vaccine Development (CHAVD), The Scripps Research Institute, La Jolla, CA 92037, USA
| | - Raiees Andrabi
- Department of Immunology and Microbiology, The Scripps Research Institute, La Jolla, CA 92037, USA; IAVI Neutralizing Antibody Center, The Scripps Research Institute, La Jolla, CA 92037, USA; Consortium for HIV/AIDS Vaccine Development (CHAVD), The Scripps Research Institute, La Jolla, CA 92037, USA
| | - Dennis R Burton
- Department of Immunology and Microbiology, The Scripps Research Institute, La Jolla, CA 92037, USA; IAVI Neutralizing Antibody Center, The Scripps Research Institute, La Jolla, CA 92037, USA; Consortium for HIV/AIDS Vaccine Development (CHAVD), The Scripps Research Institute, La Jolla, CA 92037, USA; Ragon Institute of Massachusetts General Hospital, MIT & Harvard, Cambridge, MA 02139, USA
| | - Lihong Liu
- Aaron Diamond AIDS Research Center, Columbia University Vagelos College of Physicians and Surgeons, New York, NY, USA
| | - David D Ho
- Aaron Diamond AIDS Research Center, Columbia University Vagelos College of Physicians and Surgeons, New York, NY, USA; Department of Microbiology and Immunology, Columbia University Vagelos College of Physicians and Surgeons, New York, NY 10032, USA; Division of Infectious Diseases, Department of Medicine, Columbia University Vagelos College of Physicians and Surgeons, New York, NY 10032, USA
| | - Helen Y Chu
- University of Washington, Department of Medicine, Division of Allergy and Infectious Diseases, Seattle, WA, USA
| | - Richard A Neher
- Biozentrum, University of Basel, Basel, Switzerland; Swiss Institute of Bioinformatics, Lausanne, Switzerland
| | - Jesse D Bloom
- Basic Sciences Division and Computational Biology Program, Fred Hutchinson Cancer Center, Seattle, WA 98109, USA; Howard Hughes Medical Institute, Seattle, WA 98195, USA.
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11
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Dadonaite B, Crawford KHD, Radford CE, Farrell AG, Yu TC, Hannon WW, Zhou P, Andrabi R, Burton DR, Liu L, Ho DD, Neher RA, Bloom JD. A pseudovirus system enables deep mutational scanning of the full SARS-CoV-2 spike. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2022:2022.10.13.512056. [PMID: 36263061 PMCID: PMC9580381 DOI: 10.1101/2022.10.13.512056] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
A major challenge in understanding SARS-CoV-2 evolution is interpreting the antigenic and functional effects of emerging mutations in the viral spike protein. Here we describe a new deep mutational scanning platform based on non-replicative pseudotyped lentiviruses that directly quantifies how large numbers of spike mutations impact antibody neutralization and pseudovirus infection. We demonstrate this new platform by making libraries of the Omicron BA.1 and Delta spikes. These libraries each contain ~7000 distinct amino-acid mutations in the context of up to ~135,000 unique mutation combinations. We use these libraries to map escape mutations from neutralizing antibodies targeting the receptor binding domain, N-terminal domain, and S2 subunit of spike. Overall, this work establishes a high-throughput and safe approach to measure how ~10 5 combinations of mutations affect antibody neutralization and spike-mediated infection. Notably, the platform described here can be extended to the entry proteins of many other viruses.
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Affiliation(s)
- Bernadeta Dadonaite
- Basic Sciences Division and Computational Biology Program, Fred Hutchinson Cancer Center, Seattle, Washington, 98109, USA
| | - Katharine H D Crawford
- Basic Sciences Division and Computational Biology Program, Fred Hutchinson Cancer Center, Seattle, Washington, 98109, USA
- Department of Genome Sciences & Medical Scientist Training Program, University of Washington, Seattle, Washington, 98109, USA
| | - Caelan E Radford
- Basic Sciences Division and Computational Biology Program, Fred Hutchinson Cancer Center, Seattle, Washington, 98109, USA
- Molecular and Cellular Biology Graduate Program, University of Washington, and Basic Sciences Division, Fred Hutch Cancer Center, Seattle, Washington, 98109, USA
| | - Ariana G Farrell
- Basic Sciences Division and Computational Biology Program, Fred Hutchinson Cancer Center, Seattle, Washington, 98109, USA
| | - Timothy C Yu
- Basic Sciences Division and Computational Biology Program, Fred Hutchinson Cancer Center, Seattle, Washington, 98109, USA
- Molecular and Cellular Biology Graduate Program, University of Washington, and Basic Sciences Division, Fred Hutch Cancer Center, Seattle, Washington, 98109, USA
| | - William W Hannon
- Basic Sciences Division and Computational Biology Program, Fred Hutchinson Cancer Center, Seattle, Washington, 98109, USA
- Molecular and Cellular Biology Graduate Program, University of Washington, and Basic Sciences Division, Fred Hutch Cancer Center, Seattle, Washington, 98109, USA
| | - Panpan Zhou
- Department of Immunology and Microbiology, The Scripps Research Institute, La Jolla, CA 92037, USA
- IAVI Neutralizing Antibody Center, The Scripps Research Institute, La Jolla, CA 92037, USA
- Consortium for HIV/AIDS Vaccine Development (CHAVD), The Scripps Research Institute, La Jolla, CA 92037, USA
| | - Raiees Andrabi
- Department of Immunology and Microbiology, The Scripps Research Institute, La Jolla, CA 92037, USA
- IAVI Neutralizing Antibody Center, The Scripps Research Institute, La Jolla, CA 92037, USA
- Consortium for HIV/AIDS Vaccine Development (CHAVD), The Scripps Research Institute, La Jolla, CA 92037, USA
| | - Dennis R Burton
- Department of Immunology and Microbiology, The Scripps Research Institute, La Jolla, CA 92037, USA
- IAVI Neutralizing Antibody Center, The Scripps Research Institute, La Jolla, CA 92037, USA
- Consortium for HIV/AIDS Vaccine Development (CHAVD), The Scripps Research Institute, La Jolla, CA 92037, USA
- Ragon Institute of MGH, MIT & Harvard, Cambridge, MA 02139, USA
| | - Lihong Liu
- Aaron Diamond AIDS Research Center, Columbia University Vagelos College of Physicians and Surgeons, New York, NY, USA
| | - David D. Ho
- Aaron Diamond AIDS Research Center, Columbia University Vagelos College of Physicians and Surgeons, New York, NY, USA
- Department of Microbiology and Immunology, Columbia University Vagelos College of Physicians and Surgeons, New York, NY 10032, USA
- Division of Infectious Diseases, Department of Medicine, Columbia University Vagelos College of Physicians and Surgeons, New York, NY 10032, USA
| | - Richard A. Neher
- Biozentrum, University of Basel, Basel, Switzerland, Swiss Institute of Bioinformatics, Lausanne, Switzerland
| | - Jesse D Bloom
- Basic Sciences Division and Computational Biology Program, Fred Hutchinson Cancer Center, Seattle, Washington, 98109, USA
- Howard Hughes Medical Institute, Seattle, WA, 98195, USA
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12
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Wertheim JO, Wang JC, Leelawong M, Martin DP, Havens JL, Chowdhury MA, Pekar JE, Amin H, Arroyo A, Awandare GA, Chow HY, Gonzalez E, Luoma E, Morang'a CM, Nekrutenko A, Shank SD, Silver S, Quashie PK, Rakeman JL, Ruiz V, Torian LV, Vasylyeva TI, Kosakovsky Pond SL, Hughes S. Detection of SARS-CoV-2 intra-host recombination during superinfection with Alpha and Epsilon variants in New York City. Nat Commun 2022; 13:3645. [PMID: 35752633 PMCID: PMC9233664 DOI: 10.1038/s41467-022-31247-x] [Citation(s) in RCA: 16] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2022] [Accepted: 06/08/2022] [Indexed: 01/26/2023] Open
Abstract
Recombination is an evolutionary process by which many pathogens generate diversity and acquire novel functions. Although a common occurrence during coronavirus replication, detection of recombination is only feasible when genetically distinct viruses contemporaneously infect the same host. Here, we identify an instance of SARS-CoV-2 superinfection, whereby an individual was infected with two distinct viral variants: Alpha (B.1.1.7) and Epsilon (B.1.429). This superinfection was first noted when an Alpha genome sequence failed to exhibit the classic S gene target failure behavior used to track this variant. Full genome sequencing from four independent extracts reveals that Alpha variant alleles comprise around 75% of the genomes, whereas the Epsilon variant alleles comprise around 20% of the sample. Further investigation reveals the presence of numerous recombinant haplotypes spanning the genome, specifically in the spike, nucleocapsid, and ORF 8 coding regions. These findings support the potential for recombination to reshape SARS-CoV-2 genetic diversity.
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Affiliation(s)
- Joel O Wertheim
- Department of Medicine, University of California San Diego, La Jolla, CA, USA.
| | - Jade C Wang
- New York City Public Health Laboratory, New York City Department of Health and Mental Hygiene, New York, NY, USA.
| | - Mindy Leelawong
- New York City Public Health Laboratory, New York City Department of Health and Mental Hygiene, New York, NY, USA
| | - Darren P Martin
- Institute of Infectious Diseases and Molecular Medicine, University of Cape Town, Cape Town, South Africa
| | - Jennifer L Havens
- Bioinformatics and Systems Biology Graduate Program, University of California San Diego, La Jolla, CA, USA
| | - Moinuddin A Chowdhury
- New York City Public Health Laboratory, New York City Department of Health and Mental Hygiene, New York, NY, USA
| | - Jonathan E Pekar
- Bioinformatics and Systems Biology Graduate Program, University of California San Diego, La Jolla, CA, USA
| | - Helly Amin
- New York City Public Health Laboratory, New York City Department of Health and Mental Hygiene, New York, NY, USA
| | - Anthony Arroyo
- New York City Public Health Laboratory, New York City Department of Health and Mental Hygiene, New York, NY, USA
| | - Gordon A Awandare
- West African Centre for Cell Biology of Infectious Pathogens (WACCBIP), University of Ghana, Accra, Ghana
| | - Hoi Yan Chow
- New York City Public Health Laboratory, New York City Department of Health and Mental Hygiene, New York, NY, USA
| | - Edimarlyn Gonzalez
- New York City Public Health Laboratory, New York City Department of Health and Mental Hygiene, New York, NY, USA
| | - Elizabeth Luoma
- Bureau of the Communicable Diseases, New York City Department of Health and Mental Hygiene, Long Island City, NY, USA
| | - Collins M Morang'a
- West African Centre for Cell Biology of Infectious Pathogens (WACCBIP), University of Ghana, Accra, Ghana
| | - Anton Nekrutenko
- Department of Biochemistry and Molecular Biology, The Pennsylvania State University, State College, PA, USA
| | - Stephen D Shank
- Department of Biology, Temple University, Philadelphia, PA, USA
| | - Stefan Silver
- New York City Public Health Laboratory, New York City Department of Health and Mental Hygiene, New York, NY, USA
| | - Peter K Quashie
- West African Centre for Cell Biology of Infectious Pathogens (WACCBIP), University of Ghana, Accra, Ghana
| | - Jennifer L Rakeman
- New York City Public Health Laboratory, New York City Department of Health and Mental Hygiene, New York, NY, USA
| | - Victoria Ruiz
- New York City Public Health Laboratory, New York City Department of Health and Mental Hygiene, New York, NY, USA
| | - Lucia V Torian
- New York City Public Health Laboratory, New York City Department of Health and Mental Hygiene, New York, NY, USA
| | - Tetyana I Vasylyeva
- Department of Medicine, University of California San Diego, La Jolla, CA, USA
| | | | - Scott Hughes
- New York City Public Health Laboratory, New York City Department of Health and Mental Hygiene, New York, NY, USA
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13
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RNA Structures and Their Role in Selective Genome Packaging. Viruses 2021; 13:v13091788. [PMID: 34578369 PMCID: PMC8472981 DOI: 10.3390/v13091788] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2021] [Revised: 08/31/2021] [Accepted: 09/02/2021] [Indexed: 12/13/2022] Open
Abstract
To generate infectious viral particles, viruses must specifically select their genomic RNA from milieu that contains a complex mixture of cellular or non-genomic viral RNAs. In this review, we focus on the role of viral encoded RNA structures in genome packaging. We first discuss how packaging signals are constructed from local and long-range base pairings within viral genomes, as well as inter-molecular interactions between viral and host RNAs. Then, how genome packaging is regulated by the biophysical properties of RNA. Finally, we examine the impact of RNA packaging signals on viral evolution.
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14
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Sherpa C, Rausch JW, Le Grice SFJ. HIV Genetic Diversity - Superpower of a Formidable Virus. Curr HIV Res 2021; 18:69-73. [PMID: 32223727 DOI: 10.2174/1570162x1802200311104204] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Affiliation(s)
- Chringma Sherpa
- Basic Research Laboratory Center for Cancer Research National Cancer Institute National Institute of Health Frederick, Maryland, 21702, United States
| | - Jason W Rausch
- Basic Research Laboratory Center for Cancer Research National Cancer Institute National Institute of Health Frederick, MD, 21702, United States
| | - Stuart F J Le Grice
- Basic Research Laboratory Center for Cancer Research National Cancer Institute National Institute of Health Frederick, MD, 21702, United States
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15
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Sherpa C, Le Grice SFJ. Adeno-Associated Viral Vector Mediated Expression of Broadly- Neutralizing Antibodies Against HIV-Hitting a Fast-Moving Target. Curr HIV Res 2021; 18:114-131. [PMID: 32039686 DOI: 10.2174/1570162x18666200210121339] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2019] [Revised: 01/05/2020] [Accepted: 01/16/2020] [Indexed: 12/12/2022]
Abstract
The vast genetic variability of HIV has impeded efforts towards a cure for HIV. Lifelong administration of combined antiretroviral therapy (cART) is highly effective against HIV and has markedly increased the life expectancy of HIV infected individuals. However, the long-term usage of cART is associated with co-morbidities and the emergence of multidrug-resistant escape mutants necessitating the development of alternative approaches to combat HIV/AIDS. In the past decade, the development of single-cell antibody cloning methods has facilitated the characterization of a diverse array of highly potent neutralizing antibodies against a broad range of HIV strains. Although the passive transfer of these broadly neutralizing antibodies (bnAbs) in both animal models and humans has been shown to elicit significant antiviral effects, long term virologic suppression requires repeated administration of these antibodies. Adeno-associated virus (AAV) mediated antibody gene transfer provides a long-term expression of these antibodies from a single administration of the recombinant vector. Therefore, this vectored approach holds promises in the treatment and prevention of a chronic disease like HIV infection. Here, we provide an overview of HIV genetic diversity, AAV vectorology, and anti-HIV bnAbs and summarize the promises and challenges of the application of AAV in the delivery of bnAbs for HIV prevention and therapy.
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Affiliation(s)
- Chringma Sherpa
- Basic Research Laboratory, Center for Cancer Research, National Cancer Institute, National Institute of Health, Frederick, Maryland, 21702, United States
| | - Stuart F J Le Grice
- Basic Research Laboratory, Center for Cancer Research, National Cancer Institute, National Institute of Health, Frederick, Maryland, 21702, United States
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16
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Kim HK, Yu G, Park J, Min S, Lee S, Yoon S, Kim HH. Predicting the efficiency of prime editing guide RNAs in human cells. Nat Biotechnol 2021; 39:198-206. [PMID: 32958957 DOI: 10.1038/s41587-020-0677-y] [Citation(s) in RCA: 146] [Impact Index Per Article: 48.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2020] [Accepted: 08/17/2020] [Indexed: 12/15/2022]
Abstract
Prime editing enables the introduction of virtually any small-sized genetic change without requiring donor DNA or double-strand breaks. However, evaluation of prime editing efficiency requires time-consuming experiments, and the factors that affect efficiency have not been extensively investigated. In this study, we performed high-throughput evaluation of prime editor 2 (PE2) activities in human cells using 54,836 pairs of prime editing guide RNAs (pegRNAs) and their target sequences. The resulting data sets allowed us to identify factors affecting PE2 efficiency and to develop three computational models to predict pegRNA efficiency. For a given target sequence, the computational models predict efficiencies of pegRNAs with different lengths of primer binding sites and reverse transcriptase templates for edits of various types and positions. Testing the accuracy of the predictions using test data sets that were not used for training, we found Spearman's correlations between 0.47 and 0.81. Our computational models and information about factors affecting PE2 efficiency will facilitate practical application of prime editing.
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Affiliation(s)
- Hui Kwon Kim
- Department of Pharmacology, Yonsei University College of Medicine, Seoul, Republic of Korea
- Brain Korea 21 Plus Project for Medical Sciences, Yonsei University College of Medicine, Seoul, Republic of Korea
- Center for Nanomedicine, Institute for Basic Science (IBS), Seoul, Republic of Korea
- Graduate Program of Nano Biomedical Engineering (NanoBME), Advanced Science Institute, Yonsei University, Seoul, Republic of Korea
| | - Goosang Yu
- Department of Pharmacology, Yonsei University College of Medicine, Seoul, Republic of Korea
- Brain Korea 21 Plus Project for Medical Sciences, Yonsei University College of Medicine, Seoul, Republic of Korea
| | - Jinman Park
- Department of Pharmacology, Yonsei University College of Medicine, Seoul, Republic of Korea
- Brain Korea 21 Plus Project for Medical Sciences, Yonsei University College of Medicine, Seoul, Republic of Korea
| | - Seonwoo Min
- Electrical and Computer Engineering, Seoul National University, Seoul, Republic of Korea
| | - Sungtae Lee
- Department of Pharmacology, Yonsei University College of Medicine, Seoul, Republic of Korea
| | - Sungroh Yoon
- Electrical and Computer Engineering, Seoul National University, Seoul, Republic of Korea
- Interdisciplinary Program in Bioinformatics, Seoul National University, Seoul, Republic of Korea
- Graduate School of Data Science, Seoul National University, Seoul, Republic of Korea
| | - Hyongbum Henry Kim
- Department of Pharmacology, Yonsei University College of Medicine, Seoul, Republic of Korea.
- Brain Korea 21 Plus Project for Medical Sciences, Yonsei University College of Medicine, Seoul, Republic of Korea.
- Center for Nanomedicine, Institute for Basic Science (IBS), Seoul, Republic of Korea.
- Graduate Program of Nano Biomedical Engineering (NanoBME), Advanced Science Institute, Yonsei University, Seoul, Republic of Korea.
- Severance Biomedical Science Institute, Yonsei University College of Medicine, Seoul, Republic of Korea.
- Graduate Program of NanoScience and Technology, Yonsei University, Seoul, Republic of Korea.
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17
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Kim N, Kim HK, Lee S, Seo JH, Choi JW, Park J, Min S, Yoon S, Cho SR, Kim HH. Prediction of the sequence-specific cleavage activity of Cas9 variants. Nat Biotechnol 2020; 38:1328-1336. [PMID: 32514125 DOI: 10.1038/s41587-020-0537-9] [Citation(s) in RCA: 121] [Impact Index Per Article: 30.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2019] [Revised: 04/23/2020] [Accepted: 04/27/2020] [Indexed: 12/11/2022]
Abstract
Several Streptococcus pyogenes Cas9 (SpCas9) variants have been developed to improve an enzyme's specificity or to alter or broaden its protospacer-adjacent motif (PAM) compatibility, but selecting the optimal variant for a given target sequence and application remains difficult. To build computational models to predict the sequence-specific activity of 13 SpCas9 variants, we first assessed their cleavage efficiency at 26,891 target sequences. We found that, of the 256 possible four-nucleotide NNNN sequences, 156 can be used as a PAM by at least one of the SpCas9 variants. For the high-fidelity variants, overall activity could be ranked as SpCas9 ≥ Sniper-Cas9 > eSpCas9(1.1) > SpCas9-HF1 > HypaCas9 ≈ xCas9 >> evoCas9, whereas their overall specificities could be ranked as evoCas9 >> HypaCas9 ≥ SpCas9-HF1 ≈ eSpCas9(1.1) > xCas9 > Sniper-Cas9 > SpCas9. Using these data, we developed 16 deep-learning-based computational models that accurately predict the activity of these variants at any target sequence.
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Affiliation(s)
- Nahye Kim
- Department of Pharmacology, Yonsei University College of Medicine, Seoul, Republic of Korea
- Brain Korea 21 Plus Project for Medical Sciences, Yonsei University College of Medicine, Seoul, Republic of Korea
| | - Hui Kwon Kim
- Department of Pharmacology, Yonsei University College of Medicine, Seoul, Republic of Korea
- Brain Korea 21 Plus Project for Medical Sciences, Yonsei University College of Medicine, Seoul, Republic of Korea
- Center for Nanomedicine, Institute for Basic Science (IBS), Seoul, Republic of Korea
- Graduate Program of Nano Biomedical Engineering (NanoBME), Advanced Science Institute, Yonsei University, Seoul, Republic of Korea
| | - Sungtae Lee
- Department of Pharmacology, Yonsei University College of Medicine, Seoul, Republic of Korea
| | - Jung Hwa Seo
- Brain Korea 21 Plus Project for Medical Sciences, Yonsei University College of Medicine, Seoul, Republic of Korea
- Department and Research Institute of Rehabilitation Medicine, Yonsei University College of Medicine, Seoul, Republic of Korea
| | - Jae Woo Choi
- Department of Pharmacology, Yonsei University College of Medicine, Seoul, Republic of Korea
| | - Jinman Park
- Department of Pharmacology, Yonsei University College of Medicine, Seoul, Republic of Korea
- Brain Korea 21 Plus Project for Medical Sciences, Yonsei University College of Medicine, Seoul, Republic of Korea
| | - Seonwoo Min
- Department of Electrical and Computer Engineering, Seoul National University, Seoul, Republic of Korea
| | - Sungroh Yoon
- Department of Electrical and Computer Engineering, Seoul National University, Seoul, Republic of Korea
- Interdisciplinary Program in Bioinformatics, Seoul National University, Seoul, Republic of Korea
| | - Sung-Rae Cho
- Brain Korea 21 Plus Project for Medical Sciences, Yonsei University College of Medicine, Seoul, Republic of Korea
- Department and Research Institute of Rehabilitation Medicine, Yonsei University College of Medicine, Seoul, Republic of Korea
- Graduate Program of NanoScience and Technology, Yonsei University, Seoul, Republic of Korea
| | - Hyongbum Henry Kim
- Department of Pharmacology, Yonsei University College of Medicine, Seoul, Republic of Korea.
- Brain Korea 21 Plus Project for Medical Sciences, Yonsei University College of Medicine, Seoul, Republic of Korea.
- Center for Nanomedicine, Institute for Basic Science (IBS), Seoul, Republic of Korea.
- Graduate Program of Nano Biomedical Engineering (NanoBME), Advanced Science Institute, Yonsei University, Seoul, Republic of Korea.
- Graduate Program of NanoScience and Technology, Yonsei University, Seoul, Republic of Korea.
- Severance Biomedical Science Institute, Yonsei University College of Medicine, Seoul, Republic of Korea.
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18
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Wang C, Lu T, Emanuel G, Babcock HP, Zhuang X. Imaging-based pooled CRISPR screening reveals regulators of lncRNA localization. Proc Natl Acad Sci U S A 2019; 116:10842-10851. [PMID: 31085639 PMCID: PMC6561216 DOI: 10.1073/pnas.1903808116] [Citation(s) in RCA: 73] [Impact Index Per Article: 14.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Pooled-library CRISPR screening provides a powerful means to discover genetic factors involved in cellular processes in a high-throughput manner. However, the phenotypes accessible to pooled-library screening are limited. Complex phenotypes, such as cellular morphology and subcellular molecular organization, as well as their dynamics, require imaging-based readout and are currently beyond the reach of pooled-library CRISPR screening. Here we report an all imaging-based pooled-library CRISPR screening approach that combines high-content phenotype imaging with high-throughput single guide RNA (sgRNA) identification in individual cells. In this approach, sgRNAs are codelivered to cells with corresponding barcodes placed at the 3' untranslated region of a reporter gene using a lentiviral delivery system with reduced recombination-induced sgRNA-barcode mispairing. Multiplexed error-robust fluorescence in situ hybridization (MERFISH) is used to read out the barcodes and hence identify the sgRNAs with high accuracy. We used this approach to screen 162 sgRNAs targeting 54 RNA-binding proteins for their effects on RNA localization to nuclear compartments and uncovered previously unknown regulatory factors for nuclear RNA localization. Notably, our screen revealed both positive and negative regulators for the nuclear speckle localization of a long noncoding RNA, MALAT1, suggesting a dynamic regulation of lncRNA localization in subcellular compartments.
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MESH Headings
- CRISPR-Cas Systems/genetics
- Cell Line, Tumor
- Cell Nucleus/chemistry
- Cell Nucleus/metabolism
- Gene Editing
- High-Throughput Nucleotide Sequencing/methods
- Humans
- Image Processing, Computer-Assisted/methods
- In Situ Hybridization, Fluorescence/methods
- Molecular Probes/chemistry
- Molecular Probes/genetics
- Molecular Probes/metabolism
- RNA, Guide, CRISPR-Cas Systems/chemistry
- RNA, Guide, CRISPR-Cas Systems/genetics
- RNA, Guide, CRISPR-Cas Systems/metabolism
- RNA, Long Noncoding/chemistry
- RNA, Long Noncoding/genetics
- RNA, Long Noncoding/metabolism
- RNA-Binding Proteins/chemistry
- RNA-Binding Proteins/metabolism
- Single-Cell Analysis/methods
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Affiliation(s)
- Chong Wang
- Howard Hughes Medical Institute, Harvard University, Cambridge, MA 02138
- Department of Chemistry and Chemical Biology, Harvard University, Cambridge, MA 02138
- Department of Physics, Harvard University, Cambridge, MA 02138
| | - Tian Lu
- Howard Hughes Medical Institute, Harvard University, Cambridge, MA 02138
- Department of Chemistry and Chemical Biology, Harvard University, Cambridge, MA 02138
- Department of Physics, Harvard University, Cambridge, MA 02138
| | - George Emanuel
- Howard Hughes Medical Institute, Harvard University, Cambridge, MA 02138
- Department of Chemistry and Chemical Biology, Harvard University, Cambridge, MA 02138
- Department of Physics, Harvard University, Cambridge, MA 02138
| | - Hazen P Babcock
- Center for Advanced Imaging, Harvard University, Cambridge, MA 02138
| | - Xiaowei Zhuang
- Howard Hughes Medical Institute, Harvard University, Cambridge, MA 02138;
- Department of Chemistry and Chemical Biology, Harvard University, Cambridge, MA 02138
- Department of Physics, Harvard University, Cambridge, MA 02138
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19
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Affiliation(s)
- Ruth E Hanna
- Broad Institute of MIT and Harvard, Cambridge, Massachusetts, USA
| | - John G Doench
- Broad Institute of MIT and Harvard, Cambridge, Massachusetts, USA
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20
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Ito Y, Tauzin A, Remion A, Ejima K, Mammano F, Iwami S. Dynamics of HIV-1 coinfection in different susceptible target cell populations during cell-free infection. J Theor Biol 2018; 455:39-46. [PMID: 30018001 DOI: 10.1016/j.jtbi.2018.06.025] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2018] [Revised: 05/24/2018] [Accepted: 06/28/2018] [Indexed: 12/27/2022]
Abstract
HIV-1 mutations rapidly accumulate through genetic recombination events, which require the infection of a single cell by two virions (coinfection). Accumulation of mutations in the viral population may lead to immune escape and high-level drug resistance. The existence of cell subpopulations characterized by different susceptibility to HIV-1 infection has been proposed as an important parameter driving coinfection (Dang et al., 2004). While the mechanism and the quantification of HIV-1 coinfection have been recently investigated by mathematical models, the detailed dynamics of this process during cell-free infection remains elusive. In this study, we constructed ordinary differential equations considering the heterogeneity of target cell populations during cell-free infection in cell culture, and reproduced the cell culture experimental data. Our mathematical analyses showed that the presence of two differently susceptible target cell subpopulations could explain our experimental datasets, while increasing the number of subpopulations did not improve the fitting. In addition, we quantitatively demonstrated that cells infected by multiple viruses mainly accumulated from one cell subpopulation under cell-free infection conditions. In particular, the frequency of infection events in the more susceptible subpopulation was 6.11-higher than that from the other subpopulation, and 98.3% of coinfected cells emerged from the more susceptible subpopulation. Our mathematical-experimental approach is able to extract such a quantitative information, and can be easily applied to other virus infections.
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Affiliation(s)
- Yusuke Ito
- Department of Biology, Faculty of Sciences, Kyushu University, Fukuoka 819-0395, Japan
| | - Alexandra Tauzin
- INSERM, U941, Paris 75010, France; Université Paris Diderot, Sorbonne Paris Cité, IUH, Paris 75010, France; Institut Universitaire d'Hématologie, Hôpital Saint-Louis, Paris 75010, France
| | - Azaria Remion
- INSERM, U941, Paris 75010, France; Université Paris Diderot, Sorbonne Paris Cité, IUH, Paris 75010, France; Institut Universitaire d'Hématologie, Hôpital Saint-Louis, Paris 75010, France
| | - Keisuke Ejima
- Department of Epidemiology and Biostatistics, School of Public Health, Indiana University Bloomington, IN, USA; Institute of Industrial Science, The University of Tokyo, Tokyo, Japan
| | - Fabrizio Mammano
- INSERM, U941, Paris 75010, France; Université Paris Diderot, Sorbonne Paris Cité, IUH, Paris 75010, France; Institut Universitaire d'Hématologie, Hôpital Saint-Louis, Paris 75010, France.
| | - Shingo Iwami
- Department of Biology, Faculty of Sciences, Kyushu University, Fukuoka 819-0395, Japan; PRESTO, JST, Saitama 332-0012, Japan; CREST, JST, Saitama 332-0012, Japan.
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21
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Xie S, Cooley A, Armendariz D, Zhou P, Hon GC. Frequent sgRNA-barcode recombination in single-cell perturbation assays. PLoS One 2018; 13:e0198635. [PMID: 29874289 PMCID: PMC5991360 DOI: 10.1371/journal.pone.0198635] [Citation(s) in RCA: 31] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2018] [Accepted: 05/22/2018] [Indexed: 11/18/2022] Open
Abstract
Simultaneously detecting CRISPR-based perturbations and induced transcriptional changes in the same cell is a powerful approach to unraveling genome function. Several lentiviral approaches have been developed, some of which rely on the detection of distally located genetic barcodes as an indirect proxy of sgRNA identity. Since barcodes are often several kilobases from their corresponding sgRNAs, viral recombination-mediated swapping of barcodes and sgRNAs is feasible. Using a self-circularization-based sgRNA-barcode library preparation protocol, we estimate the recombination rate to be ~50% and we trace this phenomenon to the pooled viral packaging step. Recombination is random, and decreases the signal-to-noise ratio of the assay. Our results suggest that alternative approaches can increase the throughput and sensitivity of single-cell perturbation assays.
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Affiliation(s)
- Shiqi Xie
- Cecil H. and Ida Green Center for Reproductive Biology Sciences, Department of Obstetrics and Gynecology, University of Texas Southwestern Medical Center, Dallas, Texas, United States of America
| | - Anne Cooley
- Cecil H. and Ida Green Center for Reproductive Biology Sciences, Department of Obstetrics and Gynecology, University of Texas Southwestern Medical Center, Dallas, Texas, United States of America
| | - Daniel Armendariz
- Cecil H. and Ida Green Center for Reproductive Biology Sciences, Department of Obstetrics and Gynecology, University of Texas Southwestern Medical Center, Dallas, Texas, United States of America
| | - Pei Zhou
- Cecil H. and Ida Green Center for Reproductive Biology Sciences, Department of Obstetrics and Gynecology, University of Texas Southwestern Medical Center, Dallas, Texas, United States of America
| | - Gary C. Hon
- Cecil H. and Ida Green Center for Reproductive Biology Sciences, Department of Obstetrics and Gynecology, University of Texas Southwestern Medical Center, Dallas, Texas, United States of America
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22
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López P, De Jesús O, Yamamura Y, Rodríguez N, Arias A, Sánchez R, Rodríguez Y, Tamayo-Agrait V, Cuevas W, Rivera-Amill V. Molecular Epidemiology of HIV-1 Virus in Puerto Rico: Novel Cases of HIV-1 Subtype C, D, and CRF-24BG. AIDS Res Hum Retroviruses 2018; 34:507-516. [PMID: 29658302 DOI: 10.1089/aid.2017.0305] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
HIV-1 subtype B virus is the most prevalent subtype in Puerto Rico (PR), accounting for about 90% of infection in the island. Recently, other subtypes and circulating recombinant forms (CRFs), including F(12_BF), A (01_BF), and CRF-39 BF-like, have been identified. The purpose of this study is to assess the distribution of drug resistance mutations and subtypes in PR. A total of 846 nucleotide sequences from the period comprising 2013 through 2017 were obtained from our "HIV Genotyping" test file. Phylogenetic and molecular epidemiology analyses were performed to evaluate the evolutionary dynamics and prevalence of drug resistance mutations. According to our results, we detected a decrease in the prevalence of protease inhibitor, nucleoside reverse transcriptase inhibitor (NRTI), and non-NRTI (NNRTI) resistance mutations over time. In addition, we also detected recombinant forms and, for the first time, identified subtypes C, D, and CRF-24BG in PR. Recent studies suggest that non-subtypes B are associated with a high risk of treatment failure and disease progression. The constant monitoring of viral evolution and drug resistance mutation dynamics is important to establish appropriate efforts for controlling viral expansion.
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Affiliation(s)
- Pablo López
- AIDS Research Program, Ponce Health Sciences University-School of Medicine, Ponce Research Institute, Ponce, Puerto Rico
| | - Omayra De Jesús
- AIDS Research Program, Ponce Health Sciences University-School of Medicine, Ponce Research Institute, Ponce, Puerto Rico
| | - Yasuhiro Yamamura
- AIDS Research Program, Ponce Health Sciences University-School of Medicine, Ponce Research Institute, Ponce, Puerto Rico
| | - Nayra Rodríguez
- AIDS Research Program, Ponce Health Sciences University-School of Medicine, Ponce Research Institute, Ponce, Puerto Rico
| | - Andrea Arias
- AIDS Research Program, Ponce Health Sciences University-School of Medicine, Ponce Research Institute, Ponce, Puerto Rico
| | - Raphael Sánchez
- AIDS Research Program, Ponce Health Sciences University-School of Medicine, Ponce Research Institute, Ponce, Puerto Rico
| | - Yadira Rodríguez
- AIDS Research Program, Ponce Health Sciences University-School of Medicine, Ponce Research Institute, Ponce, Puerto Rico
| | - Vivian Tamayo-Agrait
- Puerto Rico Community Network for Clinical Research on AIDS, University of Puerto Rico, Medical Sciences Campus, San Juan, Puerto Rico
| | - Wilfredo Cuevas
- HIV Clinic Outpatient Department, Ryder Memorial Hospital, Humacao, Puerto Rico
| | - Vanessa Rivera-Amill
- AIDS Research Program, Ponce Health Sciences University-School of Medicine, Ponce Research Institute, Ponce, Puerto Rico
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23
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Abstract
The evolution of viral pathogens is shaped by strong selective forces that are exerted during jumps to new hosts, confrontations with host immune responses and antiviral drugs, and numerous other processes. However, while undeniably strong and frequent, adaptive evolution is largely confined to small parts of information-packed viral genomes, and the majority of observed variation is effectively neutral. The predictions and implications of the neutral theory have proven immensely useful in this context, with applications spanning understanding within-host population structure, tracing the origins and spread of viral pathogens, predicting evolutionary dynamics, and modeling the emergence of drug resistance. We highlight the multiple ways in which the neutral theory has had an impact, which has been accelerated in the age of high-throughput, high-resolution genomics.
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Affiliation(s)
- Simon D W Frost
- Department of Veterinary Medicine, University of Cambridge, Cambridge,
United Kingdom
- The Alan Turing Institute, London, United Kingdom
| | - Brittany Rife Magalis
- Institute for Genomics and Evolutionary Medicine, Temple University,
Philadelphia, PA
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24
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Song H, Giorgi EE, Ganusov VV, Cai F, Athreya G, Yoon H, Carja O, Hora B, Hraber P, Romero-Severson E, Jiang C, Li X, Wang S, Li H, Salazar-Gonzalez JF, Salazar MG, Goonetilleke N, Keele BF, Montefiori DC, Cohen MS, Shaw GM, Hahn BH, McMichael AJ, Haynes BF, Korber B, Bhattacharya T, Gao F. Tracking HIV-1 recombination to resolve its contribution to HIV-1 evolution in natural infection. Nat Commun 2018; 9:1928. [PMID: 29765018 PMCID: PMC5954121 DOI: 10.1038/s41467-018-04217-5] [Citation(s) in RCA: 60] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2017] [Accepted: 04/10/2018] [Indexed: 11/29/2022] Open
Abstract
Recombination in HIV-1 is well documented, but its importance in the low-diversity setting of within-host diversification is less understood. Here we develop a novel computational tool (RAPR (Recombination Analysis PRogram)) to enable a detailed view of in vivo viral recombination during early infection, and we apply it to near-full-length HIV-1 genome sequences from longitudinal samples. Recombinant genomes rapidly replace transmitted/founder (T/F) lineages, with a median half-time of 27 days, increasing the genetic complexity of the viral population. We identify recombination hot and cold spots that differ from those observed in inter-subtype recombinants. Furthermore, RAPR analysis of longitudinal samples from an individual with well-characterized neutralizing antibody responses shows that recombination helps carry forward resistance-conferring mutations in the diversifying quasispecies. These findings provide insight into molecular mechanisms by which viral recombination contributes to HIV-1 persistence and immunopathogenesis and have implications for studies of HIV transmission and evolution in vivo.
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Affiliation(s)
- Hongshuo Song
- Duke Human Vaccine Institute and Department of Medicine, Duke University Medical Center, Durham, NC, 27710, USA
- United States Military HIV Research Program, Walter Reed Army Institute of Research, Silver Spring, MD, 20910, USA
| | - Elena E Giorgi
- Theoretical Division, Los Alamos National Laboratory, Los Alamos, NM, 87544, USA
| | - Vitaly V Ganusov
- Department of Microbiology, University of Tennessee, Knoxville, TN, 37996, USA
| | - Fangping Cai
- Duke Human Vaccine Institute and Department of Medicine, Duke University Medical Center, Durham, NC, 27710, USA
| | - Gayathri Athreya
- Office for Research & Discovery, University of Arizona, Tucson, AZ, 85721, USA
| | - Hyejin Yoon
- Theoretical Division, Los Alamos National Laboratory, Los Alamos, NM, 87544, USA
| | - Oana Carja
- Department of Biology, University of Pennsylvania, Philadelphia, PA, 19104, USA
| | - Bhavna Hora
- Duke Human Vaccine Institute and Department of Medicine, Duke University Medical Center, Durham, NC, 27710, USA
| | - Peter Hraber
- Theoretical Division, Los Alamos National Laboratory, Los Alamos, NM, 87544, USA
| | | | - Chunlai Jiang
- Duke Human Vaccine Institute and Department of Medicine, Duke University Medical Center, Durham, NC, 27710, USA
- National Engineering Laboratory For AIDS Vaccine, College of Life Science, Jilin University, Changchun, Jilin, 130012, China
| | - Xiaojun Li
- Duke Human Vaccine Institute and Department of Medicine, Duke University Medical Center, Durham, NC, 27710, USA
| | - Shuyi Wang
- Department of Medicine, University of Pennsylvania, Philadelphia, PA, 19104, USA
| | - Hui Li
- Department of Medicine, University of Pennsylvania, Philadelphia, PA, 19104, USA
| | - Jesus F Salazar-Gonzalez
- Department of Medicine, University of Alabama at Birmingham, Birmingham, AL, 35294, USA
- MRC/UVRI and LSHTM Uganda Research Unit, Plot 51-57, Nakiwogo Road, Entebbe, Uganda
| | - Maria G Salazar
- Department of Medicine, University of Alabama at Birmingham, Birmingham, AL, 35294, USA
| | - Nilu Goonetilleke
- Departments of Microbiology and Immunology & Medicine, University of North Carolina at Chapel Hill, Chapel Hill, NC, 27599, USA
| | - Brandon F Keele
- AIDS and Cancer Virus Program, Frederick National Laboratory for Cancer Research, Frederick, MD, 21702, USA
| | - David C Montefiori
- Duke Human Vaccine Institute and Department of Medicine, Duke University Medical Center, Durham, NC, 27710, USA
| | - Myron S Cohen
- Departments of Microbiology and Immunology & Medicine, University of North Carolina at Chapel Hill, Chapel Hill, NC, 27599, USA
| | - George M Shaw
- Department of Medicine, University of Pennsylvania, Philadelphia, PA, 19104, USA
- Department of Microbiology, University of Pennsylvania, Philadelphia, PA, 19104, USA
| | - Beatrice H Hahn
- Department of Medicine, University of Pennsylvania, Philadelphia, PA, 19104, USA
- Department of Microbiology, University of Pennsylvania, Philadelphia, PA, 19104, USA
| | - Andrew J McMichael
- Weatherall Institute of Molecular Medicine, University of Oxford, Oxford, OX3 9DS, UK
| | - Barton F Haynes
- Duke Human Vaccine Institute and Department of Medicine, Duke University Medical Center, Durham, NC, 27710, USA
| | - Bette Korber
- Theoretical Division, Los Alamos National Laboratory, Los Alamos, NM, 87544, USA
| | - Tanmoy Bhattacharya
- Theoretical Division, Los Alamos National Laboratory, Los Alamos, NM, 87544, USA
- Santa Fe Institute, Santa Fe, NM, 87501, USA
| | - Feng Gao
- Duke Human Vaccine Institute and Department of Medicine, Duke University Medical Center, Durham, NC, 27710, USA.
- National Engineering Laboratory For AIDS Vaccine, College of Life Science, Jilin University, Changchun, Jilin, 130012, China.
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25
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Hill AJ, McFaline-Figueroa JL, Starita LM, Gasperini MJ, Matreyek KA, Packer J, Jackson D, Shendure J, Trapnell C. On the design of CRISPR-based single-cell molecular screens. Nat Methods 2018; 15:271-274. [PMID: 29457792 PMCID: PMC5882576 DOI: 10.1038/nmeth.4604] [Citation(s) in RCA: 131] [Impact Index Per Article: 21.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2017] [Accepted: 01/06/2018] [Indexed: 01/05/2023]
Abstract
Several groups recently coupled CRISPR perturbations and single-cell RNA-seq for pooled genetic screens. We demonstrate that vector designs of these studies are susceptible to ∼50% swapping of guide RNA-barcode associations because of lentiviral template switching. We optimized a published alternative, CROP-seq, in which the guide RNA also serves as the barcode, and here confirm that this strategy performs robustly and doubled the rate at which guides are assigned to cells to 94%.
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Affiliation(s)
- Andrew J Hill
- Department of Genome Sciences, University of Washington, Seattle, Washington, USA
| | | | - Lea M Starita
- Department of Genome Sciences, University of Washington, Seattle, Washington, USA
| | - Molly J Gasperini
- Department of Genome Sciences, University of Washington, Seattle, Washington, USA
| | - Kenneth A Matreyek
- Department of Genome Sciences, University of Washington, Seattle, Washington, USA
| | - Jonathan Packer
- Department of Genome Sciences, University of Washington, Seattle, Washington, USA
| | - Dana Jackson
- Department of Genome Sciences, University of Washington, Seattle, Washington, USA
| | - Jay Shendure
- Department of Genome Sciences, University of Washington, Seattle, Washington, USA
- Howard Hughes Medical Institute, Seattle, Washington, USA
| | - Cole Trapnell
- Department of Genome Sciences, University of Washington, Seattle, Washington, USA
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26
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Dubois N, Marquet R, Paillart JC, Bernacchi S. Retroviral RNA Dimerization: From Structure to Functions. Front Microbiol 2018; 9:527. [PMID: 29623074 PMCID: PMC5874298 DOI: 10.3389/fmicb.2018.00527] [Citation(s) in RCA: 55] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2018] [Accepted: 03/08/2018] [Indexed: 01/18/2023] Open
Abstract
The genome of the retroviruses is a dimer composed by two homologous copies of genomic RNA (gRNA) molecules of positive polarity. The dimerization process allows two gRNA molecules to be non-covalently linked together through intermolecular base-pairing. This step is critical for the viral life cycle and is highly conserved among retroviruses with the exception of spumaretroviruses. Furthermore, packaging of two gRNA copies into viral particles presents an important evolutionary advantage for immune system evasion and drug resistance. Recent studies reported RNA switches models regulating not only gRNA dimerization, but also translation and packaging, and a spatio-temporal characterization of viral gRNA dimerization within cells are now at hand. This review summarizes our current understanding on the structural features of the dimerization signals for a variety of retroviruses (HIVs, MLV, RSV, BLV, MMTV, MPMV…), the mechanisms of RNA dimer formation and functional implications in the retroviral cycle.
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Affiliation(s)
- Noé Dubois
- Architecture et Réactivité de l'ARN, UPR 9002, IBMC, CNRS, Université de Strasbourg, Strasbourg, France
| | - Roland Marquet
- Architecture et Réactivité de l'ARN, UPR 9002, IBMC, CNRS, Université de Strasbourg, Strasbourg, France
| | - Jean-Christophe Paillart
- Architecture et Réactivité de l'ARN, UPR 9002, IBMC, CNRS, Université de Strasbourg, Strasbourg, France
| | - Serena Bernacchi
- Architecture et Réactivité de l'ARN, UPR 9002, IBMC, CNRS, Université de Strasbourg, Strasbourg, France
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27
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Matreyek KA, Stephany JJ, Fowler DM. A platform for functional assessment of large variant libraries in mammalian cells. Nucleic Acids Res 2017; 45:e102. [PMID: 28335006 PMCID: PMC5499817 DOI: 10.1093/nar/gkx183] [Citation(s) in RCA: 79] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2016] [Accepted: 03/08/2017] [Indexed: 01/01/2023] Open
Abstract
Sequencing-based, massively parallel genetic assays have revolutionized our ability to quantify the relationship between many genotypes and a phenotype of interest. Unfortunately, variant library expression platforms in mammalian cells are far from ideal, hindering the study of human gene variants in their physiologically relevant cellular contexts. Here, we describe a platform for phenotyping variant libraries in transfectable mammalian cell lines in two steps. First, a landing pad cell line with a genomically integrated, Tet-inducible cassette containing a Bxb1 recombination site is created. Second, a single variant from a library of transfected, promoter-less plasmids is recombined into the landing pad in each cell. Thus, every cell in the recombined pool expresses a single variant, allowing for parallel, sequencing-based assessment of variant effect. We describe a method for incorporating a single landing pad into a defined site of a cell line of interest, and show that our approach can be used generate more than 20 000 recombinant cells in a single experiment. Finally, we use our platform in combination with a sequencing-based assay to explore the N-end rule by simultaneously measuring the effects of all possible N-terminal amino acids on protein expression.
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Affiliation(s)
- Kenneth A Matreyek
- Department of Genome Sciences, University of Washington, Seattle, WA 98195, USA
| | - Jason J Stephany
- Department of Bioengineering, University of Washington, Seattle, WA 98195, USA
| | - Douglas M Fowler
- Department of Genome Sciences, University of Washington, Seattle, WA 98195, USA.,Department of Bioengineering, University of Washington, Seattle, WA 98195, USA
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28
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29
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Doekes HM, Fraser C, Lythgoe KA. Effect of the Latent Reservoir on the Evolution of HIV at the Within- and Between-Host Levels. PLoS Comput Biol 2017; 13:e1005228. [PMID: 28103248 PMCID: PMC5245781 DOI: 10.1371/journal.pcbi.1005228] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2016] [Accepted: 10/31/2016] [Indexed: 02/06/2023] Open
Abstract
The existence of long-lived reservoirs of latently infected CD4+ T cells is the major barrier to curing HIV, and has been extensively studied in this light. However, the effect of these reservoirs on the evolutionary dynamics of the virus has received little attention. Here, we present a within-host quasispecies model that incorporates a long-lived reservoir, which we then nest into an epidemiological model of HIV dynamics. For biologically plausible parameter values, we find that the presence of a latent reservoir can severely delay evolutionary dynamics within a single host, with longer delays associated with larger relative reservoir sizes and/or homeostatic proliferation of cells within the reservoir. These delays can fundamentally change the dynamics of the virus at the epidemiological scale. In particular, the delay in within-host evolutionary dynamics can be sufficient for the virus to evolve intermediate viral loads consistent with maximising transmission, as is observed, and not the very high viral loads that previous models have predicted, an effect that can be further enhanced if viruses similar to those that initiate infection are preferentially transmitted. These results depend strongly on within-host characteristics such as the relative reservoir size, with the evolution of intermediate viral loads observed only when the within-host dynamics are sufficiently delayed. In conclusion, we argue that the latent reservoir has important, and hitherto under-appreciated, roles in both within- and between-host viral evolution.
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Affiliation(s)
- Hilje M. Doekes
- Department of Infectious Disease Epidemiology, Imperial College London, London, United Kingdom
- Theoretical Biology, Utrecht University, Utrecht, The Netherlands
| | - Christophe Fraser
- Department of Infectious Disease Epidemiology, Imperial College London, London, United Kingdom
- Oxford Big Data Institute, Li Ka Shing Centre for Health Information and Discovery, Nuffield Department of Medicine, University of Oxford, Oxford, United Kingdom
| | - Katrina A. Lythgoe
- Department of Infectious Disease Epidemiology, Imperial College London, London, United Kingdom
- Department of Zoology, University of Oxford, Oxford, United Kingdom
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30
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Menéndez-Arias L, Sebastián-Martín A, Álvarez M. Viral reverse transcriptases. Virus Res 2016; 234:153-176. [PMID: 28043823 DOI: 10.1016/j.virusres.2016.12.019] [Citation(s) in RCA: 48] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2016] [Revised: 12/19/2016] [Accepted: 12/24/2016] [Indexed: 12/11/2022]
Abstract
Reverse transcriptases (RTs) play a major role in the replication of Retroviridae, Metaviridae, Pseudoviridae, Hepadnaviridae and Caulimoviridae. RTs are enzymes that are able to synthesize DNA using RNA or DNA as templates (DNA polymerase activity), and degrade RNA when forming RNA/DNA hybrids (ribonuclease H activity). In retroviruses and LTR retrotransposons (Metaviridae and Pseudoviridae), the coordinated action of both enzymatic activities converts single-stranded RNA into a double-stranded DNA that is flanked by identical sequences known as long terminal repeats (LTRs). RTs of retroviruses and LTR retrotransposons are active as monomers (e.g. murine leukemia virus RT), homodimers (e.g. Ty3 RT) or heterodimers (e.g. human immunodeficiency virus type 1 (HIV-1) RT). RTs lack proofreading activity and display high intrinsic error rates. Besides, high recombination rates observed in retroviruses are promoted by poor processivity that causes template switching, a hallmark of reverse transcription. HIV-1 RT inhibitors acting on its polymerase activity constitute the backbone of current antiretroviral therapies, although novel drugs, including ribonuclease H inhibitors, are still necessary to fight HIV infections. In Hepadnaviridae and Caulimoviridae, reverse transcription leads to the formation of nicked circular DNAs that will be converted into episomal DNA in the host cell nucleus. Structural and biochemical information on their polymerases is limited, although several drugs inhibiting HIV-1 RT are known to be effective against the human hepatitis B virus polymerase. In this review, we summarize current knowledge on reverse transcription in the five virus families and discuss available biochemical and structural information on RTs, including their biosynthesis, enzymatic activities, and potential inhibition.
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Affiliation(s)
- Luis Menéndez-Arias
- Centro de Biología Molecular "Severo Ochoa", Consejo Superior de Investigaciones Científicas and Universidad Autónoma de Madrid, c/Nicolás Cabrera, 1, Campus de Cantoblanco, 28049 Madrid, Spain.
| | - Alba Sebastián-Martín
- Centro de Biología Molecular "Severo Ochoa", Consejo Superior de Investigaciones Científicas and Universidad Autónoma de Madrid, c/Nicolás Cabrera, 1, Campus de Cantoblanco, 28049 Madrid, Spain
| | - Mar Álvarez
- Centro de Biología Molecular "Severo Ochoa", Consejo Superior de Investigaciones Científicas and Universidad Autónoma de Madrid, c/Nicolás Cabrera, 1, Campus de Cantoblanco, 28049 Madrid, Spain
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31
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Abstract
Antiviral drug resistance is a matter of great clinical importance that, historically, has been investigated mostly from a virological perspective. Although the proximate mechanisms of resistance can be readily uncovered using these methods, larger evolutionary trends often remain elusive. Recent interest by population geneticists in studies of antiviral resistance has spurred new metrics for evaluating mutation and recombination rates, demographic histories of transmission and compartmentalization, and selective forces incurred during viral adaptation to antiviral drug treatment. We present up-to-date summaries on antiviral resistance for a range of drugs and viral types, and review recent advances for studying their evolutionary histories. We conclude that information imparted by demographic and selective histories, as revealed through population genomic inference, is integral to assessing the evolution of antiviral resistance as it pertains to human health.
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Affiliation(s)
- Kristen K Irwin
- School of Life Sciences, École Polytechnique Fédéral de Lausanne (EPFL), Lausanne, Switzerland.,Swiss Institute of Bioinformatics (SIB), Lausanne, Switzerland
| | - Nicholas Renzette
- Department of Microbiology and Physiological Systems, University of Massachusetts Medical School, Worcester, Massachusetts, USA
| | - Timothy F Kowalik
- Department of Microbiology and Physiological Systems, University of Massachusetts Medical School, Worcester, Massachusetts, USA
| | - Jeffrey D Jensen
- School of Life Sciences, École Polytechnique Fédéral de Lausanne (EPFL), Lausanne, Switzerland.,Swiss Institute of Bioinformatics (SIB), Lausanne, Switzerland
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32
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Cromer D, Schlub TE, Smyth RP, Grimm AJ, Chopra A, Mallal S, Davenport MP, Mak J. HIV-1 Mutation and Recombination Rates Are Different in Macrophages and T-cells. Viruses 2016; 8:118. [PMID: 27110814 PMCID: PMC4848610 DOI: 10.3390/v8040118] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2015] [Revised: 04/05/2016] [Accepted: 04/19/2016] [Indexed: 11/16/2022] Open
Abstract
High rates of mutation and recombination help human immunodeficiency virus (HIV) to evade the immune system and develop resistance to antiretroviral therapy. Macrophages and T-cells are the natural target cells of HIV-1 infection. A consensus has not been reached as to whether HIV replication results in differential recombination between primary T-cells and macrophages. Here, we used HIV with silent mutation markers along with next generation sequencing to compare the mutation and the recombination rates of HIV directly in T lymphocytes and macrophages. We observed a more than four-fold higher recombination rate of HIV in macrophages compared to T-cells (p < 0.001) and demonstrated that this difference is not due to different reliance on C-X-C chemokine receptor type 4 (CXCR4) and C-C chemokine receptor type 5 (CCR5) co-receptors between T-cells and macrophages. We also found that the pattern of recombination across the HIV genome (hot and cold spots) remains constant between T-cells and macrophages despite a three-fold increase in the overall recombination rate. This indicates that the difference in rates is a general feature of HIV DNA synthesis during macrophage infection. In contrast to HIV recombination, we found that T-cells have a 30% higher mutation rate than macrophages (p < 0.001) and that the mutational profile is similar between these cell types. Unexpectedly, we found no association between mutation and recombination in macrophages, in contrast to T-cells. Our data highlights some of the fundamental difference of HIV recombination and mutation amongst these two major target cells of infection. Understanding these differences will provide invaluable insights toward HIV evolution and how the virus evades immune surveillance and anti-retroviral therapeutics.
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Affiliation(s)
- Deborah Cromer
- Infection Analytics Program, Kirby Institute, UNSW Australia, Sydney NSW 2052, Australia.
- Centre for Vascular Research, UNSW Australia, Sydney NSW 2052, Australia.
| | - Timothy E Schlub
- Sydney School of Public Health, Sydney Medical School, University of Sydney, Sydney NSW 2006, Australia.
| | - Redmond P Smyth
- Centre for Virology, Burnet Institute, Melbourne VIC 3004, Australia.
- Architecture et Réactivité de l'ARN, IBMC, CNRS, Université de Strasbourg, 67084 Strasbourg, France.
| | - Andrew J Grimm
- Infection Analytics Program, Kirby Institute, UNSW Australia, Sydney NSW 2052, Australia.
| | - Abha Chopra
- Institute for Immunology and Infectious Diseases (IIID), Murdoch University, Perth WA 6150, Australia.
| | - Simon Mallal
- Institute for Immunology and Infectious Diseases (IIID), Murdoch University, Perth WA 6150, Australia.
| | - Miles P Davenport
- Infection Analytics Program, Kirby Institute, UNSW Australia, Sydney NSW 2052, Australia.
- Centre for Vascular Research, UNSW Australia, Sydney NSW 2052, Australia.
| | - Johnson Mak
- Biosecurity Flagship, CSIRO (AAHL), Geelong VIC 3220, Australia.
- School of Medicine, Deakin University and CSIRO (AAHL), Geelong VIC 3216, Australia.
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33
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Abstract
BACKGROUND HIV recombination has been estimated in vitro using a variety of approaches, and shows a high rate of template switching per reverse transcription event. In-vivo studies of recombination generally measure the accumulation of recombinant strains over time, and thus do not directly estimate a comparable template switching rate. METHOD To examine whether the estimated in-vitro template switching rate is representative of the rate that occurs during HIV infection in vivo, we adopted a novel approach, analysing single genome sequences from early founder viruses to study the in-vivo template switching rate in the env region of HIV. RESULTS We estimated the in-vivo per cycle template switching rate to be between 0.5 and 1.5/1000 nt, or approximately 5-14 recombination events over the length of the HIV genome. CONCLUSION The in-vivo estimated template switching rate is close to the in-vitro estimated rate found in primary T lymphocytes but not macrophages, which is consistent with the majority of HIV infection occurring in T lymphocytes.
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34
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A general method to eliminate laboratory induced recombinants during massive, parallel sequencing of cDNA library. Virol J 2015; 12:55. [PMID: 25879746 PMCID: PMC4403950 DOI: 10.1186/s12985-015-0280-x] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2014] [Accepted: 03/16/2015] [Indexed: 01/09/2023] Open
Abstract
BACKGROUND Massive, parallel sequencing is a potent tool for dissecting the regulation of biological processes by revealing the dynamics of the cellular RNA profile under different conditions. Similarly, massive, parallel sequencing can be used to reveal the complexity of viral quasispecies that are often found in the RNA virus infected host. However, the production of cDNA libraries for next-generation sequencing (NGS) necessitates the reverse transcription of RNA into cDNA and the amplification of the cDNA template using PCR, which may introduce artefact in the form of phantom nucleic acids species that can bias the composition and interpretation of original RNA profiles. METHOD Using HIV as a model we have characterised the major sources of error during the conversion of viral RNA to cDNA, namely excess RNA template and the RNaseH activity of the polymerase enzyme, reverse transcriptase. In addition we have analysed the effect of PCR cycle on detection of recombinants and assessed the contribution of transfection of highly similar plasmid DNA to the formation of recombinant species during the production of our control viruses. RESULTS We have identified RNA template concentrations, RNaseH activity of reverse transcriptase, and PCR conditions as key parameters that must be carefully optimised to minimise chimeric artefacts. CONCLUSIONS Using our optimised RT-PCR conditions, in combination with our modified PCR amplification procedure, we have developed a reliable technique for accurate determination of RNA species using NGS technology.
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Pérez-Losada M, Arenas M, Galán JC, Palero F, González-Candelas F. Recombination in viruses: mechanisms, methods of study, and evolutionary consequences. INFECTION, GENETICS AND EVOLUTION : JOURNAL OF MOLECULAR EPIDEMIOLOGY AND EVOLUTIONARY GENETICS IN INFECTIOUS DISEASES 2015; 30:296-307. [PMID: 25541518 PMCID: PMC7106159 DOI: 10.1016/j.meegid.2014.12.022] [Citation(s) in RCA: 198] [Impact Index Per Article: 22.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/23/2014] [Revised: 12/15/2014] [Accepted: 12/17/2014] [Indexed: 02/08/2023]
Abstract
Recombination is a pervasive process generating diversity in most viruses. It joins variants that arise independently within the same molecule, creating new opportunities for viruses to overcome selective pressures and to adapt to new environments and hosts. Consequently, the analysis of viral recombination attracts the interest of clinicians, epidemiologists, molecular biologists and evolutionary biologists. In this review we present an overview of three major areas related to viral recombination: (i) the molecular mechanisms that underlie recombination in model viruses, including DNA-viruses (Herpesvirus) and RNA-viruses (Human Influenza Virus and Human Immunodeficiency Virus), (ii) the analytical procedures to detect recombination in viral sequences and to determine the recombination breakpoints, along with the conceptual and methodological tools currently used and a brief overview of the impact of new sequencing technologies on the detection of recombination, and (iii) the major areas in the evolutionary analysis of viral populations on which recombination has an impact. These include the evaluation of selective pressures acting on viral populations, the application of evolutionary reconstructions in the characterization of centralized genes for vaccine design, and the evaluation of linkage disequilibrium and population structure.
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Affiliation(s)
- Marcos Pérez-Losada
- CIBIO, Centro de Investigação em Biodiversidade e Recursos Genéticos, Universidade do Porto, Campus Agrário de Vairão, Portugal; Computational Biology Institute, George Washington University, Ashburn, VA 20147, USA
| | - Miguel Arenas
- Centre for Molecular Biology "Severo Ochoa", Consejo Superior de Investigaciones Científicas (CSIC), Madrid, Spain
| | - Juan Carlos Galán
- Servicio de Microbiología, Hospital Ramón y Cajal and Instituto Ramón y Cajal de Investigación Sanitaria (IRYCIS), Madrid, Spain; CIBER en Epidemiología y Salud Pública, Spain
| | - Ferran Palero
- CIBER en Epidemiología y Salud Pública, Spain; Unidad Mixta Infección y Salud Pública, FISABIO-Universitat de València, Valencia, Spain
| | - Fernando González-Candelas
- CIBER en Epidemiología y Salud Pública, Spain; Unidad Mixta Infección y Salud Pública, FISABIO-Universitat de València, Valencia, Spain.
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Rawson JMO, Mansky LM. Retroviral vectors for analysis of viral mutagenesis and recombination. Viruses 2014; 6:3612-42. [PMID: 25254386 PMCID: PMC4189041 DOI: 10.3390/v6093612] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2014] [Revised: 09/15/2014] [Accepted: 09/17/2014] [Indexed: 12/29/2022] Open
Abstract
Retrovirus population diversity within infected hosts is commonly high due in part to elevated rates of replication, mutation, and recombination. This high genetic diversity often complicates the development of effective diagnostics, vaccines, and antiviral drugs. This review highlights the diverse vectors and approaches that have been used to examine mutation and recombination in retroviruses. Retroviral vectors for these purposes can broadly be divided into two categories: those that utilize reporter genes as mutation or recombination targets and those that utilize viral genes as targets of mutation or recombination. Reporter gene vectors greatly facilitate the detection, quantification, and characterization of mutants and/or recombinants, but may not fully recapitulate the patterns of mutagenesis or recombination observed in native viral gene sequences. In contrast, the detection of mutations or recombination events directly in viral genes is more biologically relevant but also typically more challenging and inefficient. We will highlight the advantages and disadvantages of the various vectors and approaches used as well as propose ways in which they could be improved.
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Affiliation(s)
- Jonathan M O Rawson
- Institute for Molecular Virology, University of Minnesota, Moos Tower 18-242, 515 Delaware St SE, Minneapolis, MN 55455, USA.
| | - Louis M Mansky
- Institute for Molecular Virology, University of Minnesota, Moos Tower 18-242, 515 Delaware St SE, Minneapolis, MN 55455, USA.
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da Silva J, Wyatt SK. Fitness valleys constrain HIV-1's adaptation to its secondary chemokine coreceptor. J Evol Biol 2014; 27:604-15. [DOI: 10.1111/jeb.12329] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2013] [Accepted: 01/04/2014] [Indexed: 12/15/2022]
Affiliation(s)
- J. da Silva
- School of Molecular and Biomedical Science; University of Adelaide; Adelaide SA Australia
| | - S. K. Wyatt
- School of Molecular and Biomedical Science; University of Adelaide; Adelaide SA Australia
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Fifteen to twenty percent of HIV substitution mutations are associated with recombination. J Virol 2014; 88:3837-49. [PMID: 24453357 DOI: 10.1128/jvi.03136-13] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
HIV undergoes high rates of mutation and recombination during reverse transcription, but it is not known whether these events occur independently or are linked mechanistically. Here we used a system of silent marker mutations in HIV and a single round of infection in primary T lymphocytes combined with a high-throughput sequencing and mathematical modeling approach to directly estimate the viral recombination and mutation rates. From >7 million nucleotides (nt) of sequences from HIV infection, we observed 4,801 recombination events and 859 substitution mutations (≈1.51 and 0.12 events per 1,000 nt, respectively). We used experimental controls to account for PCR-induced and transfection-induced recombination and sequencing error. We found that the single-cycle virus-induced mutation rate is 4.6 × 10(-5) mutations per nt after correction. By sorting of our data into recombined and nonrecombined sequences, we found a significantly higher mutation rate in recombined regions (P = 0.003 by Fisher's exact test). We used a permutation approach to eliminate a number of potential confounding factors and confirm that mutation occurs around the site of recombination and is not simply colocated in the genome. By comparing mutation rates in recombined and nonrecombined regions, we found that recombination-associated mutations account for 15 to 20% of all mutations occurring during reverse transcription.
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Abstract
UNLABELLED HIV-1 infection is characterized by the rapid generation of genetic diversity that facilitates viral escape from immune selection and antiretroviral therapy. Despite recombination's crucial role in viral diversity and evolution, little is known about the genomic factors that influence recombination between highly similar genomes. In this study, we use a minimally modified full-length HIV-1 genome and high-throughput sequence analysis to study recombination in gag and pol in T cells. We find that recombination is favored at a number of recombination hot spots, where recombination occurs six times more frequently than at corresponding cold spots. Interestingly, these hot spots occur near important features of the HIV-1 genome but do not occur at sites immediately around protease inhibitor or reverse transcriptase inhibitor drug resistance mutations. We show that the recombination hot and cold spots are consistent across five blood donors and are independent of coreceptor-mediated entry. Finally, we check common experimental confounders and find that these are not driving the location of recombination hot spots. This is the first study to identify the location of recombination hot spots between two similar viral genomes with great statistical power and under conditions that closely reflect natural recombination events among HIV-1 quasispecies. IMPORTANCE The ability of HIV-1 to evade the immune system and antiretroviral therapy depends on genetic diversity within the viral quasispecies. Retroviral recombination is an important mechanism that helps to generate and maintain this genetic diversity, but little is known about how recombination rates vary within the HIV-1 genome. We measured recombination rates in gag and pol and identified recombination hot and cold spots, demonstrating that recombination is not random but depends on the underlying gene sequence. The strength and location of these recombination hot and cold spots can be used to improve models of viral dynamics and evolution, which will be useful for the design of robust antiretroviral therapies.
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Di Giallonardo F, Zagordi O, Duport Y, Leemann C, Joos B, Künzli-Gontarczyk M, Bruggmann R, Beerenwinkel N, Günthard HF, Metzner KJ. Next-generation sequencing of HIV-1 RNA genomes: determination of error rates and minimizing artificial recombination. PLoS One 2013; 8:e74249. [PMID: 24058534 PMCID: PMC3776835 DOI: 10.1371/journal.pone.0074249] [Citation(s) in RCA: 50] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2013] [Accepted: 07/31/2013] [Indexed: 12/28/2022] Open
Abstract
Next-generation sequencing (NGS) is a valuable tool for the detection and quantification of HIV-1 variants in vivo. However, these technologies require detailed characterization and control of artificially induced errors to be applicable for accurate haplotype reconstruction. To investigate the occurrence of substitutions, insertions, and deletions at the individual steps of RT-PCR and NGS, 454 pyrosequencing was performed on amplified and non-amplified HIV-1 genomes. Artificial recombination was explored by mixing five different HIV-1 clonal strains (5-virus-mix) and applying different RT-PCR conditions followed by 454 pyrosequencing. Error rates ranged from 0.04-0.66% and were similar in amplified and non-amplified samples. Discrepancies were observed between forward and reverse reads, indicating that most errors were introduced during the pyrosequencing step. Using the 5-virus-mix, non-optimized, standard RT-PCR conditions introduced artificial recombinants in a fraction of at least 30% of the reads that subsequently led to an underestimation of true haplotype frequencies. We minimized the fraction of recombinants down to 0.9-2.6% by optimized, artifact-reducing RT-PCR conditions. This approach enabled correct haplotype reconstruction and frequency estimations consistent with reference data obtained by single genome amplification. RT-PCR conditions are crucial for correct frequency estimation and analysis of haplotypes in heterogeneous virus populations. We developed an RT-PCR procedure to generate NGS data useful for reliable haplotype reconstruction and quantification.
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Affiliation(s)
- Francesca Di Giallonardo
- Division of Infectious Diseases and Hospital Epidemiology, University Hospital Zurich, University of Zurich, Zurich, Switzerland
| | - Osvaldo Zagordi
- Department of Biosystems Sciences and Engineering, ETH Zurich, Basel, Switzerland
- Institute of Medical Virology, University of Zurich, Zurich, Switzerland
| | - Yannick Duport
- Division of Infectious Diseases and Hospital Epidemiology, University Hospital Zurich, University of Zurich, Zurich, Switzerland
| | - Christine Leemann
- Division of Infectious Diseases and Hospital Epidemiology, University Hospital Zurich, University of Zurich, Zurich, Switzerland
| | - Beda Joos
- Division of Infectious Diseases and Hospital Epidemiology, University Hospital Zurich, University of Zurich, Zurich, Switzerland
| | | | - Rémy Bruggmann
- Functional Genomics Center Zurich (FGCZ), University of Zurich, ETH Zurich, Zurich, Switzerland
| | - Niko Beerenwinkel
- Department of Biosystems Sciences and Engineering, ETH Zurich, Basel, Switzerland
- SIB Swiss Institute of Bioinformatics, Basel, Switzerland
| | - Huldrych F. Günthard
- Division of Infectious Diseases and Hospital Epidemiology, University Hospital Zurich, University of Zurich, Zurich, Switzerland
| | - Karin J. Metzner
- Division of Infectious Diseases and Hospital Epidemiology, University Hospital Zurich, University of Zurich, Zurich, Switzerland
- * E-mail:
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Smith SA, Wood C, West JT. HIV-1 Env C2-V4 diversification in a slow-progressor infant reveals a flat but rugged fitness landscape. PLoS One 2013; 8:e63094. [PMID: 23638182 PMCID: PMC3639246 DOI: 10.1371/journal.pone.0063094] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2013] [Accepted: 03/28/2013] [Indexed: 11/19/2022] Open
Abstract
Human immunodeficiency virus type-1 (HIV-1) fitness has been associated with virus entry, a process mediated by the envelope glycoprotein (Env). We previously described Env genetic diversification in a Zambian, subtype C infected, slow-progressor child (1157i) in parallel with an evolving neutralizing antibody response. Because of the role the Variable-3 loop (V3) plays in transmission, cell tropism, neutralization sensitivity, and fitness, longitudinally isolated 1157i C2-V4 alleles were cloned into HIV-1NL4-3-eGFP and -DsRed2 infectious molecular clones. The fluorescent reporters allowed for dual-infection competitions between all patient-derived C2-V4 chimeras to quantify the effect of V3 diversification and selection on fitness. 'Winners' and 'losers' were readily discriminated among the C2-V4 alleles. Exceptional sensitivity for detection of subtle fitness differences was revealed through analysis of two alleles differing in a single synonymous amino acid. However, when the outcomes of N = 33 competitions were averaged for each chimera, the aggregate analysis showed that despite increasing diversification and divergence with time, natural selection of C2-V4 sequences in this individual did not appear to be producing a 'survival of the fittest' evolutionary pattern. Rather, we detected a relatively flat fitness landscape consistent with mutational robustness. Fitness outcomes were then correlated with individual components of the entry process. Env incorporation into particles correlated best with fitness, suggesting a role for Env avidity, as opposed to receptor/coreceptor affinity, in defining fitness. Nevertheless, biochemical analyses did not identify any step in HIV-1 entry as a dominant determinant of fitness. Our results lead us to conclude that multiple aspects of entry contribute to maintaining adequate HIV-1 fitness, and there is no surrogate analysis for determining fitness. The capacity for subtle polymorphisms in Env to nevertheless significantly impact viral fitness suggests fitness is best defined by head-to-head competition.
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Affiliation(s)
- S. Abigail Smith
- Department of Microbiology and Immunology, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma, United States of America
| | - Charles Wood
- Nebraska Center for Virology, University of Nebraska, Lincoln, Nebraska, United States of America
- School of Biological Sciences, University of Nebraska, Lincoln, Nebraska, United States of America
| | - John T. West
- Department of Microbiology and Immunology, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma, United States of America
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Brégnard C, Pacini G, Danos O, Basmaciogullari S. Suboptimal provirus expression explains apparent nonrandom cell coinfection with HIV-1. J Virol 2012; 86:8810-20. [PMID: 22696639 PMCID: PMC3421764 DOI: 10.1128/jvi.00831-12] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2012] [Accepted: 06/04/2012] [Indexed: 11/20/2022] Open
Abstract
Despite the ability of primate lentiviruses to prevent infected cells from being reinfected, cell coinfection has occurred in the past and has shaped virus evolution by promoting the biogenesis of heterozygous virions and recombination during reverse transcription. In vitro experiments have shown that cell coinfection with HIV is more frequent than would be expected if coinfection were a random process. A possible explanation for this bias is the heterogeneity of target cells and the preferred infection of a subpopulation. To address this question, we compared the frequency of double-positive cells measured following coincubation with green fluorescent protein (GFP) and DsRed HIV reporter viruses with that of stochastic coinfection calculated as the product of the frequencies of GFP- and DsRed-positive cells upon incubation with either reporter virus. Coinfection was more frequent than would be expected on the grounds of stochastic infection, due to the underestimation of single-infection frequencies, which mathematically decreased the calculated frequency. Indeed, when cells were incubated with either reporter virus, a fraction of the cells were scored as uninfected yet harbored a silent provirus that was reactivated upon coinfection through cross talk between viral elements. When such cross talk was avoided, experimental and calculated coinfection frequencies matched, indicating random coinfection. The proportion of infected cells harboring a silent provirus was estimated from coinfection experiments and was shown to be cell type dependent but independent of the virus entry route.
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Affiliation(s)
- Christelle Brégnard
- Hôpital Necker-Enfants Malades, Université Paris Descartes, Sorbonne Paris Cité, Paris, France
- Université Paris Diderot, Sorbonne Paris Cité, Paris, France
- Inserm U845, Paris, France
| | - Gregory Pacini
- Hôpital Necker-Enfants Malades, Université Paris Descartes, Sorbonne Paris Cité, Paris, France
- Université Paris Diderot, Sorbonne Paris Cité, Paris, France
- Inserm U845, Paris, France
| | - Olivier Danos
- Hôpital Necker-Enfants Malades, Université Paris Descartes, Sorbonne Paris Cité, Paris, France
- Inserm U845, Paris, France
- Cancer Institute, University College London, London, United Kingdom
| | - Stéphane Basmaciogullari
- Hôpital Necker-Enfants Malades, Université Paris Descartes, Sorbonne Paris Cité, Paris, France
- Inserm U845, Paris, France
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Smyth RP, Davenport MP, Mak J. The origin of genetic diversity in HIV-1. Virus Res 2012; 169:415-29. [PMID: 22728444 DOI: 10.1016/j.virusres.2012.06.015] [Citation(s) in RCA: 71] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2012] [Revised: 06/10/2012] [Accepted: 06/12/2012] [Indexed: 10/28/2022]
Abstract
One of the hallmarks of HIV infection is the rapid development of a genetically complex population (quasispecies) from an initially limited number of infectious particles. Genetic diversity remains one of the major obstacles to eradication of HIV. The viral quasispecies can respond rapidly to selective pressures, such as that imposed by the immune system and antiretroviral therapy, and frustrates vaccine design efforts. Two unique features of retroviral replication are responsible for the unprecedented variation generated during infection. First, mutations are frequently introduced into the viral genome by the error prone viral reverse transcriptase and through the actions of host cellular factors, such as the APOBEC family of nucleic acid editing enzymes. Second, the HIV reverse transcriptase can utilize both copies of the co-packaged viral genome in a process termed retroviral recombination. When the co-packaged viral genomes are genetically different, retroviral recombination can lead to the shuffling of mutations between viral genomes in the quasispecies. This review outlines the stages of the retroviral life cycle where genetic variation is introduced, focusing on the principal mechanisms of mutation and recombination. Understanding the mechanistic origin of genetic diversity is essential to combating HIV.
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Affiliation(s)
- Redmond P Smyth
- Centre for Virology, Burnet Institute, 85 Commercial Road, Melbourne, Victoria 3004, Australia
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44
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Abstract
Evolution of RNA viruses occurs through disequilibria of collections of closely related mutant spectra or mutant clouds termed viral quasispecies. Here we review the origin of the quasispecies concept and some biological implications of quasispecies dynamics. Two main aspects are addressed: (i) mutant clouds as reservoirs of phenotypic variants for virus adaptability and (ii) the internal interactions that are established within mutant spectra that render a virus ensemble the unit of selection. The understanding of viruses as quasispecies has led to new antiviral designs, such as lethal mutagenesis, whose aim is to drive viruses toward low fitness values with limited chances of fitness recovery. The impact of quasispecies for three salient human pathogens, human immunodeficiency virus and the hepatitis B and C viruses, is reviewed, with emphasis on antiviral treatment strategies. Finally, extensions of quasispecies to nonviral systems are briefly mentioned to emphasize the broad applicability of quasispecies theory.
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Affiliation(s)
- Esteban Domingo
- Centro de Biología Molecular Severo Ochoa (CSIC-UAM), C/ Nicolás Cabrera, Universidad Autónoma de Madrid, Cantoblanco, Madrid, Spain.
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da Silva J. The dynamics of HIV-1 adaptation in early infection. Genetics 2012; 190:1087-99. [PMID: 22209906 PMCID: PMC3296244 DOI: 10.1534/genetics.111.136366] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2011] [Accepted: 12/18/2011] [Indexed: 11/18/2022] Open
Abstract
Human immunodeficiency virus type 1 (HIV-1) undergoes a severe population bottleneck during sexual transmission and yet adapts extremely rapidly to the earliest immune responses. The bottleneck has been inferred to typically consist of a single genome, and typically eight amino acid mutations in viral proteins spread to fixation by the end of the early chronic phase of infection in response to selection by CD8(+) T cells. Stochastic simulation was used to examine the effects of the transmission bottleneck and of potential interference among spreading immune-escape mutations on the adaptive dynamics of the virus in early infection. If major viral population genetic parameters are assigned realistic values that permit rapid adaptive evolution, then a bottleneck of a single genome is not inconsistent with the observed pattern of adaptive fixations. One requirement is strong selection by CD8(+) T cells that decreases over time. Such selection may reduce effective population sizes at linked loci through genetic hitchhiking. However, this effect is predicted to be minor in early infection because the transmission bottleneck reduces the effective population size to such an extent that the resulting strong selection and weak mutation cause beneficial mutations to fix sequentially and thus avoid interference.
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Affiliation(s)
- Jack da Silva
- School of Molecular and Biomedical Science, University of Adelaide, Adelaide, SA 5005, Australia.
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46
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Castro-Nallar E, Pérez-Losada M, Burton GF, Crandall KA. The evolution of HIV: inferences using phylogenetics. Mol Phylogenet Evol 2012; 62:777-92. [PMID: 22138161 PMCID: PMC3258026 DOI: 10.1016/j.ympev.2011.11.019] [Citation(s) in RCA: 63] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2011] [Revised: 11/17/2011] [Accepted: 11/21/2011] [Indexed: 12/02/2022]
Abstract
Molecular phylogenetics has revolutionized the study of not only evolution but also disparate fields such as genomics, bioinformatics, epidemiology, ecology, microbiology, molecular biology and biochemistry. Particularly significant are its achievements in population genetics as a result of the development of coalescent theory, which have contributed to more accurate model-based parameter estimation and explicit hypothesis testing. The study of the evolution of many microorganisms, and HIV in particular, have benefited from these new methodologies. HIV is well suited for such sophisticated population analyses because of its large population sizes, short generation times, high substitution rates and relatively small genomes. All these factors make HIV an ideal and fascinating model to study molecular evolution in real time. Here we review the significant advances made in HIV evolution through the application of phylogenetic approaches. We first examine the relative roles of mutation and recombination on the molecular evolution of HIV and its adaptive response to drug therapy and tissue allocation. We then review some of the fundamental questions in HIV evolution in relation to its origin and diversification and describe some of the insights gained using phylogenies. Finally, we show how phylogenetic analysis has advanced our knowledge of HIV dynamics (i.e., phylodynamics).
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Affiliation(s)
- Eduardo Castro-Nallar
- Department of Biology, 401 Widtsoe Building, Brigham Young University, Provo, UT 84602-5181, USA.
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47
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Pond SLK, Murrell B, Poon AFY. Evolution of viral genomes: interplay between selection, recombination, and other forces. Methods Mol Biol 2012; 856:239-72. [PMID: 22399462 DOI: 10.1007/978-1-61779-585-5_10] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
RNA viruses evolve very rapidly, often recombine, and are subject to strong host (immune response) and anthropogenic (antiretroviral drugs) selective forces. Given their compact and extensively sequenced genomes, comparative analysis of RNA viral data can provide important insights into the molecular mechanisms of adaptation, pathogenicity, immune evasion, and drug resistance. In this chapter, we present an example-based overview of recent advances in evolutionary models and statistical approaches that enable screening viral alignments for evidence of adaptive change in the presence of recombination, detecting bursts of directional adaptive evolution associated with the phenotypic changes, and detecting of coevolving sites in viral genes.
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48
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Abstract
Throughout the living world, genetic recombination and nucleotide substitution are the primary processes that create the genetic variation upon which natural selection acts. Just as analyses of substitution patterns can reveal a great deal about evolution, so too can analyses of recombination. Evidence of genetic recombination within the genomes of apparently asexual species can equate with evidence of cryptic sexuality. In sexually reproducing species, nonrandom patterns of sequence exchange can provide direct evidence of population subdivisions that prevent certain individuals from mating. Although an interesting topic in its own right, an important reason for analysing recombination is to account for its potentially disruptive influences on various phylogenetic-based molecular evolution analyses. Specifically, the evolutionary histories of recombinant sequences cannot be accurately described by standard bifurcating phylogenetic trees. Taking recombination into account can therefore be pivotal to the success of selection, molecular clock and various other analyses that require adequate modelling of shared ancestry and draw increased power from accurately inferred phylogenetic trees. Here, we review various computational approaches to studying recombination and provide guidelines both on how to gain insights into this important evolutionary process and on how it can be properly accounted for during molecular evolution studies.
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Affiliation(s)
- Darren P Martin
- Computational Biology Group, Institute of Infectious Diseases and Molecular Medicine, University of Cape Town, Cape Town, South Africa
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49
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Smyth RP, Schlub TE, Grimm A, Venturi V, Chopra A, Mallal S, Davenport MP, Mak J. Reducing chimera formation during PCR amplification to ensure accurate genotyping. Gene 2010; 469:45-51. [PMID: 20833233 DOI: 10.1016/j.gene.2010.08.009] [Citation(s) in RCA: 77] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2010] [Revised: 08/27/2010] [Accepted: 08/30/2010] [Indexed: 11/28/2022]
Abstract
Measurements of population diversity are fundamental to the reconstruction of the evolutionary and epidemiological history of organisms. Commonly used protocols to measure population diversity using the polymerase chain reaction (PCR) are prone to the introduction of artificial chimeras. These are often difficult to detect and can confound the correct interpretation of results due to the false generation of recombinants when the underlying DNA sample contains multiple distinct templates. This study presents a standardised procedure to suppress the formation of artificial chimeras during PCR amplification. The solution is based on the accurate determination of the efficiency and end point of the log-linear phase of a PCR. This procedure will facilitate the generation of data sets that more accurately reflect the underlying population diversity rather than artifacts introduced by the process itself.
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Affiliation(s)
- R P Smyth
- Centre for Virology, Burnet Institute, 85 Commercial Road, Melbourne, Victoria, Australia
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