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Meng H, Mou C, Zhang L, Zhou J, Lu T, Chen Z. The roles of 6K protein on Getah virus replication and pathogenicity. J Med Virol 2023; 95:e29302. [PMID: 38084773 DOI: 10.1002/jmv.29302] [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: 09/09/2023] [Revised: 10/31/2023] [Accepted: 11/25/2023] [Indexed: 12/18/2023]
Abstract
Alphavirus is a type of arbovirus that can infect both humans and animals. The amino acid sequence of the 6K protein, being one of the structural proteins of the alphavirus, is not conserved. Deletion of this protein will result in varying effects on different alphaviruses. Our study focuses on the function of the Getah virus (GETV) 6K protein in infected cells and mice. We successfully constructed infectious clone plasmids and created resulting viruses (rGETV and rGETV-Δ6K). Our comprehensive microscopic analysis revealed that the 6 K protein mainly stays in the endoplasmic reticulum. In addition, rGETV-Δ6K has lower thermal stability and sensitivity to temperature than GETV. Although the deletion of the 6K protein does not reduce virion production in ST cells, it affects the release of virions from host cells by inhibiting the process of E2 protein transportation to the plasma membrane. Subsequent in vivo testing demonstrated that neonatal mice infected with rGETV-Δ6K had a lower virus content, less significant pathological changes in tissue slices, and milder disease than those infected with the wild-type virus. Our results indicate that the 6K protein effectively reduces the viral titer by influencing the release of viral particles. Furthermore, the 6K protein play a role in the clinical manifestation of GETV disease.
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Affiliation(s)
- Hui Meng
- College of Veterinary Medicine, Yangzhou University, Yangzhou, Jiangsu, China
| | - Chunxiao Mou
- College of Veterinary Medicine, Yangzhou University, Yangzhou, Jiangsu, China
- Joint International Research Laboratory of Agriculture and Agri-Product Safety, the Ministry of Education of China, Yangzhou University, Yangzhou, Jiangsu, China
- Jiangsu Co-Innovation Center for Prevention and Control of Important Animal Infectious Diseases and Zoonoses, Yangzhou University, Yangzhou, Jiangsu, China
| | - Liangjiu Zhang
- College of Veterinary Medicine, Yangzhou University, Yangzhou, Jiangsu, China
| | - Jingye Zhou
- College of Veterinary Medicine, Yangzhou University, Yangzhou, Jiangsu, China
| | - Tianyuan Lu
- College of Veterinary Medicine, Yangzhou University, Yangzhou, Jiangsu, China
| | - Zhenhai Chen
- College of Veterinary Medicine, Yangzhou University, Yangzhou, Jiangsu, China
- Joint International Research Laboratory of Agriculture and Agri-Product Safety, the Ministry of Education of China, Yangzhou University, Yangzhou, Jiangsu, China
- Jiangsu Co-Innovation Center for Prevention and Control of Important Animal Infectious Diseases and Zoonoses, Yangzhou University, Yangzhou, Jiangsu, China
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Hucke FIL, Bestehorn-Willmann M, Bassetto M, Brancale A, Zanetta P, Bugert JJ. CHIKV strains Brazil (wt) and Ross (lab-adapted) differ with regard to cell host range and antiviral sensitivity and show CPE in human glioblastoma cell lines U138 and U251. Virus Genes 2022; 58:188-202. [PMID: 35347588 PMCID: PMC8960095 DOI: 10.1007/s11262-022-01892-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/28/2021] [Accepted: 03/01/2022] [Indexed: 11/24/2022]
Abstract
Chikungunya virus (CHIKV), a (re)emerging arbovirus, is the causative agent of chikungunya fever. To date, no approved vaccine or specific antiviral therapy are available. CHIKV has repeatedly been responsible for serious economic and public health impacts in countries where CHIKV epidemics occurred. Antiviral tests in vitro are generally performed in Vero-B4 cells, a well characterised cell line derived from the kidney of an African green monkey. In this work we characterised a CHIKV patient isolate from Brazil (CHIKVBrazil) with regard to cell affinity, infectivity, propagation and cell damage and compared it with a high-passage lab strain (CHIKVRoss). Infecting various cell lines (Vero-B4, A549, Huh-7, DBTRG, U251, and U138) with both virus strains, we found distinct differences between the two viruses. CHIKVBrazil does not cause cytopathic effects (CPE) in the human hepatocarcinoma cell line Huh-7. Neither CHIKVBrazil nor CHIKVRoss caused CPE on A549 human lung epithelial cells. The human astrocyte derived glioblastoma cell lines U138 and U251 were found to be effective models for lytic infection with both virus strains and we discuss their predictive potential for neurogenic CHIKV disease. We also detected significant differences in antiviral efficacies regarding the two CHIKV strains. Generally, the antivirals ribavirin, hydroxychloroquine (HCQ) and T-1105 seem to work better against CHIKVBrazil in glioblastoma cells than in Vero-B4. Finally, full genome analyses of the CHIKV isolates were done in order to determine their lineage and possibly explain differences in tissue range and antiviral compound efficacies.
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Affiliation(s)
- Friederike I L Hucke
- Bundeswehr Institute of Microbiology, Neuherbergstraße 11, 80937, Munich, Germany.
| | | | - Marcella Bassetto
- Department of Chemistry, Faculty of Science and Engineering, Swansea University, Swansea, UK
| | - Andrea Brancale
- Cardiff School of Pharmacy and Pharmaceutical Sciences, Cardiff University, Cardiff, UK
| | - Paola Zanetta
- Laboratory of Applied Microbiology, Center for Translational Research on Allergic and Autoimmune Diseases (CAAD), Department of Health Sciences (DISS), School of Medicine, Università del Piemonte Orientale (UPO), 28100, Novara, Italy
| | - Joachim J Bugert
- Bundeswehr Institute of Microbiology, Neuherbergstraße 11, 80937, Munich, Germany
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3
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Constant LEC, Rajsfus BF, Carneiro PH, Sisnande T, Mohana-Borges R, Allonso D. Overview on Chikungunya Virus Infection: From Epidemiology to State-of-the-Art Experimental Models. Front Microbiol 2021; 12:744164. [PMID: 34675908 PMCID: PMC8524093 DOI: 10.3389/fmicb.2021.744164] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2021] [Accepted: 09/07/2021] [Indexed: 12/27/2022] Open
Abstract
Chikungunya virus (CHIKV) is currently one of the most relevant arboviruses to public health. It is a member of the Togaviridae family and alphavirus genus and causes an arthritogenic disease known as chikungunya fever (CHIKF). It is characterized by a multifaceted disease, which is distinguished from other arbovirus infections by the intense and debilitating arthralgia that can last for months or years in some individuals. Despite the great social and economic burden caused by CHIKV infection, there is no vaccine or specific antiviral drugs currently available. Recent outbreaks have shown a change in the severity profile of the disease in which atypical and severe manifestation lead to hundreds of deaths, reinforcing the necessity to understand the replication and pathogenesis processes. CHIKF is a complex disease resultant from the infection of a plethora of cell types. Although there are several in vivo models for studying CHIKV infection, none of them reproduces integrally the disease signature observed in humans, which is a challenge for vaccine and drug development. Therefore, understanding the potentials and limitations of the state-of-the-art experimental models is imperative to advance in the field. In this context, the present review outlines the present knowledge on CHIKV epidemiology, replication, pathogenesis, and immunity and also brings a critical perspective on the current in vitro and in vivo state-of-the-art experimental models of CHIKF.
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Affiliation(s)
- Larissa E. C. Constant
- Departamento de Biotecnologia Farmacêutica, Faculdade de Farmácia, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil
- Laboratório de Biotecnologia e Bioengenharia Estrutural, Instituto de Biofísica Carlos Chagas Filho, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil
| | - Bia F. Rajsfus
- Departamento de Biotecnologia Farmacêutica, Faculdade de Farmácia, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil
- Laboratório de Biotecnologia e Bioengenharia Estrutural, Instituto de Biofísica Carlos Chagas Filho, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil
| | - Pedro H. Carneiro
- Laboratório de Biotecnologia e Bioengenharia Estrutural, Instituto de Biofísica Carlos Chagas Filho, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil
| | - Tháyna Sisnande
- Laboratório de Biotecnologia e Bioengenharia Estrutural, Instituto de Biofísica Carlos Chagas Filho, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil
| | - Ronaldo Mohana-Borges
- Laboratório de Biotecnologia e Bioengenharia Estrutural, Instituto de Biofísica Carlos Chagas Filho, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil
| | - Diego Allonso
- Departamento de Biotecnologia Farmacêutica, Faculdade de Farmácia, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil
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Elmasri Z, Nasal BL, Jose J. Alphavirus-Induced Membrane Rearrangements during Replication, Assembly, and Budding. Pathogens 2021; 10:984. [PMID: 34451448 PMCID: PMC8399458 DOI: 10.3390/pathogens10080984] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2021] [Revised: 07/30/2021] [Accepted: 08/02/2021] [Indexed: 01/01/2023] Open
Abstract
Alphaviruses are arthropod-borne viruses mainly transmitted by hematophagous insects that cause moderate to fatal disease in humans and other animals. Currently, there are no approved vaccines or antivirals to mitigate alphavirus infections. In this review, we summarize the current knowledge of alphavirus-induced structures and their functions in infected cells. Throughout their lifecycle, alphaviruses induce several structural modifications, including replication spherules, type I and type II cytopathic vacuoles, and filopodial extensions. Type I cytopathic vacuoles are replication-induced structures containing replication spherules that are sites of RNA replication on the endosomal and lysosomal limiting membrane. Type II cytopathic vacuoles are assembly induced structures that originate from the Golgi apparatus. Filopodial extensions are induced at the plasma membrane and are involved in budding and cell-to-cell transport of virions. This review provides an overview of the viral and host factors involved in the biogenesis and function of these virus-induced structures. Understanding virus-host interactions in infected cells will lead to the identification of new targets for antiviral discovery.
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Affiliation(s)
- Zeinab Elmasri
- Huck Institutes of the Life Sciences, The Pennsylvania State University, University Park, PA 16802, USA;
- Department of Biochemistry & Molecular Biology, Eberly College of Science, The Pennsylvania State University, University Park, PA 16802, USA;
| | - Benjamin L. Nasal
- Department of Biochemistry & Molecular Biology, Eberly College of Science, The Pennsylvania State University, University Park, PA 16802, USA;
| | - Joyce Jose
- Huck Institutes of the Life Sciences, The Pennsylvania State University, University Park, PA 16802, USA;
- Department of Biochemistry & Molecular Biology, Eberly College of Science, The Pennsylvania State University, University Park, PA 16802, USA;
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Maljkovic Berry I, Eyase F, Pollett S, Konongoi SL, Joyce MG, Figueroa K, Ofula V, Koka H, Koskei E, Nyunja A, Mancuso JD, Jarman RG, Sang R. Global Outbreaks and Origins of a Chikungunya Virus Variant Carrying Mutations Which May Increase Fitness for Aedes aegypti: Revelations from the 2016 Mandera, Kenya Outbreak. Am J Trop Med Hyg 2020; 100:1249-1257. [PMID: 30860010 PMCID: PMC6493958 DOI: 10.4269/ajtmh.18-0980] [Citation(s) in RCA: 38] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Abstract
In 2016, a chikungunya virus (CHIKV) outbreak was reported in Mandera, Kenya. This was the first major CHIKV outbreak in the country since the global reemergence of this virus in Kenya in 2004. We collected samples and sequenced viral genomes from this outbreak. All Kenyan genomes contained two mutations, E1:K211E and E2:V264A, recently reported to have an association with increased infectivity, dissemination, and transmission in the Aedes aegypti vector. Phylogeographic inference of temporal and spatial virus relationships showed that this variant emerged within the East, Central, and South African lineage between 2005 and 2008, most probably in India. It was also in India where the first large outbreak caused by this virus appeared, in New Delhi, 2010. More importantly, our results also showed that this variant is no longer contained to India. We found it present in several major outbreaks, including the 2016 outbreaks in Pakistan and Kenya, and the 2017 outbreak in Bangladesh. Thus, this variant may have a capability of driving large CHIKV outbreaks in different regions of the world. Our results point to the importance of continued genomic-based surveillance and prompt urgent vector competence studies to assess the level of vector susceptibility and virus transmission, and the impact this might have on this variant's epidemic potential and global spread.
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Affiliation(s)
- Irina Maljkovic Berry
- Viral Diseases Branch, Walter Reed Army Institute of Research, Silver Spring, Maryland
| | - Fredrick Eyase
- United States Army Medical Research Directorate - Kenya, Nairobi, Kenya
| | - Simon Pollett
- Viral Diseases Branch, Walter Reed Army Institute of Research, Silver Spring, Maryland
| | - Samson Limbaso Konongoi
- Center for Virus Research, Kenya Medical Research Institute, Nairobi, Kenya.,United States Army Medical Research Directorate - Kenya, Nairobi, Kenya
| | - Michael Gordon Joyce
- Henry M. Jackson Foundation for the Advancement of Military Medicine, Inc., Bethesda, Maryland.,Military HIV Research Program, Walter Reed Army Institute of Research, Silver Spring, Maryland
| | - Katherine Figueroa
- Viral Diseases Branch, Walter Reed Army Institute of Research, Silver Spring, Maryland
| | - Victor Ofula
- United States Army Medical Research Directorate - Kenya, Nairobi, Kenya
| | - Helen Koka
- United States Army Medical Research Directorate - Kenya, Nairobi, Kenya
| | - Edith Koskei
- United States Army Medical Research Directorate - Kenya, Nairobi, Kenya
| | - Albert Nyunja
- United States Army Medical Research Directorate - Kenya, Nairobi, Kenya
| | - James D Mancuso
- United States Army Medical Research Directorate - Kenya, Nairobi, Kenya
| | - Richard G Jarman
- Viral Diseases Branch, Walter Reed Army Institute of Research, Silver Spring, Maryland
| | - Rosemary Sang
- United States Army Medical Research Directorate - Kenya, Nairobi, Kenya
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Brown RS, Wan JJ, Kielian M. The Alphavirus Exit Pathway: What We Know and What We Wish We Knew. Viruses 2018; 10:E89. [PMID: 29470397 PMCID: PMC5850396 DOI: 10.3390/v10020089] [Citation(s) in RCA: 60] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2018] [Revised: 02/19/2018] [Accepted: 02/20/2018] [Indexed: 12/28/2022] Open
Abstract
Alphaviruses are enveloped positive sense RNA viruses and include serious human pathogens, such as the encephalitic alphaviruses and Chikungunya virus. Alphaviruses are transmitted to humans primarily by mosquito vectors and include species that are classified as emerging pathogens. Alphaviruses assemble highly organized, spherical particles that bud from the plasma membrane. In this review, we discuss what is known about the alphavirus exit pathway during a cellular infection. We describe the viral protein interactions that are critical for virus assembly/budding and the host factors that are involved, and we highlight the recent discovery of cell-to-cell transmission of alphavirus particles via intercellular extensions. Lastly, we discuss outstanding questions in the alphavirus exit pathway that may provide important avenues for future research.
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Affiliation(s)
- Rebecca S Brown
- Department of Cell Biology, Albert Einstein College of Medicine, Bronx, NY 10461, USA.
| | - Judy J Wan
- Department of Cell Biology, Albert Einstein College of Medicine, Bronx, NY 10461, USA.
| | - Margaret Kielian
- Department of Cell Biology, Albert Einstein College of Medicine, Bronx, NY 10461, USA.
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An Alphavirus E2 Membrane-Proximal Domain Promotes Envelope Protein Lateral Interactions and Virus Budding. mBio 2017; 8:mBio.01564-17. [PMID: 29114027 PMCID: PMC5676042 DOI: 10.1128/mbio.01564-17] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023] Open
Abstract
Alphaviruses are members of a group of small enveloped RNA viruses that includes important human pathogens such as Chikungunya virus and the equine encephalitis viruses. The virus membrane is covered by a lattice composed of 80 spikes, each a trimer of heterodimers of the E2 and E1 transmembrane proteins. During virus endocytic entry, the E1 glycoprotein mediates the low-pH-dependent fusion of the virus membrane with the endosome membrane, thus initiating virus infection. While much is known about E1 structural rearrangements during membrane fusion, it is unclear how the E1/E2 dimer dissociates, a step required for the fusion reaction. A recent Alphavirus cryo-electron microscopy reconstruction revealed a previously unidentified D subdomain in the E2 ectodomain, close to the virus membrane. A loop within this region, here referred to as the D-loop, contains two highly conserved histidines, H348 and H352, which were hypothesized to play a role in dimer dissociation. We generated Semliki Forest virus mutants containing the single and double alanine substitutions H348A, H352A, and H348/352A. The three D-loop mutations caused a reduction in virus growth ranging from 1.6 to 2 log but did not significantly affect structural protein biosynthesis or transport, dimer stability, virus fusion, or specific infectivity. Instead, growth reduction was due to inhibition of a late stage of virus assembly at the plasma membrane. The virus particles that are produced show reduced thermostability compared to the wild type. We propose the E2 D-loop as a key region in establishing the E1-E2 contacts that drive glycoprotein lattice formation and promote Alphavirus budding from the plasma membrane. Alphavirus infection causes severe and debilitating human diseases for which there are no effective antiviral therapies or vaccines. In order to develop targeted therapeutics, detailed molecular understanding of the viral entry and exit mechanisms is required. In this report, we define the role of the E2 protein juxtamembrane D-loop, which contains highly conserved histidine residues at positions 348 and 352. These histidines do not play an important role in virus fusion and infection. However, mutation of the D-loop histidines causes significant decreases in the assembly and thermostability of Alphavirus particles. Our results suggest that the E2 D-loop interacts with the E1 protein to promote Alphavirus budding.
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Zheng Y, Kielian M. An alphavirus temperature-sensitive capsid mutant reveals stages of nucleocapsid assembly. Virology 2015; 484:412-420. [PMID: 26051211 DOI: 10.1016/j.virol.2015.05.011] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2015] [Revised: 05/05/2015] [Accepted: 05/12/2015] [Indexed: 11/17/2022]
Abstract
Alphaviruses have a nucleocapsid core composed of the RNA genome surrounded by an icosahedral lattice of capsid protein. An insertion after position 186 in the capsid protein produced a strongly temperature-sensitive growth phenotype. Even when the structural proteins were synthesized at the permissive temperature (28°C), subsequent incubation of the cells at the non-permissive temperature (37°C) dramatically decreased mutant capsid protein stability and particle assembly. Electron microscopy confirmed the presence of cytoplasmic nucleocapsids in mutant-infected cells cultured at the permissive temperature, but these nucleocapsids were not stable to sucrose gradient separation. In contrast, nucleocapsids isolated from mutant virus particles had similar stability to that of wildtype virus. Our data support a model in which cytoplasmic nucleocapsids go through a maturation step during packaging into virus particles. The insertion site lies in the interface between capsid proteins in the assembled nucleocapsid, suggesting the region where such a stabilizing transition occurs.
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Affiliation(s)
- Yan Zheng
- Department of Cell Biology, Albert Einstein College of Medicine, Bronx, New York, USA.
| | - Margaret Kielian
- Department of Cell Biology, Albert Einstein College of Medicine, Bronx, New York, USA.
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Wagner JM, Pajerowski JD, Daniels CL, McHugh PM, Flynn JA, Balliet JW, Casimiro DR, Subramanian S. Enhanced production of Chikungunya virus-like particles using a high-pH adapted spodoptera frugiperda insect cell line. PLoS One 2014; 9:e94401. [PMID: 24713807 PMCID: PMC3979839 DOI: 10.1371/journal.pone.0094401] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2014] [Accepted: 03/14/2014] [Indexed: 11/18/2022] Open
Abstract
Chikungunya virus-like particles (VLPs) have potential to be used as a prophylactic vaccine based on testing in multiple animal models and are currently being evaluated for human use in a Phase I clinical trial. The current method for producing these enveloped alphavirus VLPs by transient gene expression in mammalian cells presents challenges for scalable and robust industrial manufacturing, so the insect cell baculovirus expression vector system was evaluated as an alternative expression technology. Subsequent to recombinant baculovirus infection of Sf21 cells in standard culture media (pH 6.2–6.4), properly processed Chikungunya structural proteins were detected and assembled capsids were observed. However, an increase in culture pH to 6.6–6.8 was necessary to produce detectable concentrations of assembled VLPs. Since this elevated production pH exceeds the optimum for growth medium stability and Sf21 culture, medium modifications were made and a novel insect cell variant (SfBasic) was derived by exposure of Sf21 to elevated culture pH for a prolonged period of time. The high-pH adapted SfBasic insect cell line described herein is capable of maintaining normal cell growth into the typical mammalian cell culture pH range of 7.0–7.2 and produces 11-fold higher Chikungunya VLP yields relative to the parental Sf21 cell line. After scale-up into stirred tank bioreactors, SfBasic derived VLPs were chromatographically purified and shown to be similar in size and structure to a VLP standard derived from transient gene expression in HEK293 cells. Total serum anti-Chikungunya IgG and neutralizing titers from guinea pigs vaccinated with SfBasic derived VLPs or HEK293 derived VLPs were not significantly different with respect to production method, suggesting that this adapted insect cell line and production process could be useful for manufacturing Chikungunya VLPs for use as a vaccine. The adaptation of Sf21 to produce high levels of recombinant protein and VLPs in an elevated pH range may also have applications for other pH-sensitive protein or VLP targets.
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Affiliation(s)
- James M. Wagner
- Vaccine Research and Development, Merck Research Laboratories, Merck & Co., Inc., West Point, Pennsylvania, United States of America
| | - J. David Pajerowski
- Vaccine Research and Development, Merck Research Laboratories, Merck & Co., Inc., West Point, Pennsylvania, United States of America
| | - Christopher L. Daniels
- Vaccine Research and Development, Merck Research Laboratories, Merck & Co., Inc., West Point, Pennsylvania, United States of America
| | - Patrick M. McHugh
- Vaccine Research and Development, Merck Research Laboratories, Merck & Co., Inc., West Point, Pennsylvania, United States of America
| | - Jessica A. Flynn
- Vaccine Research and Development, Merck Research Laboratories, Merck & Co., Inc., West Point, Pennsylvania, United States of America
| | - John W. Balliet
- Vaccine Research and Development, Merck Research Laboratories, Merck & Co., Inc., West Point, Pennsylvania, United States of America
| | - Danilo R. Casimiro
- Vaccine Research and Development, Merck Research Laboratories, Merck & Co., Inc., West Point, Pennsylvania, United States of America
| | - Shyamsundar Subramanian
- Vaccine Research and Development, Merck Research Laboratories, Merck & Co., Inc., West Point, Pennsylvania, United States of America
- * E-mail:
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10
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A key interaction between the alphavirus envelope proteins responsible for initial dimer dissociation during fusion. J Virol 2013; 87:3774-81. [PMID: 23325694 DOI: 10.1128/jvi.03310-12] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
Alphaviruses such as Semliki Forest virus (SFV) are enveloped viruses whose surface is covered by an organized lattice composed of trimers of E2-E1 heterodimers. The E1 envelope protein, a class II fusion protein, contains the hydrophobic fusion loop and refolds to drive virus fusion with the endosome membrane. The E2 protein is synthesized as a precursor p62, whose processing by furin primes the heterodimer for dissociation during virus entry. Dissociation of the E2-E1 heterodimer is an essential step during low-pH-triggered fusion, while the dissociation of the immature p62-E1 dimer is relatively pH resistant. Previous structural studies described an "acid-sensitive region" in E2 that becomes disordered at low pH. Within this region, the conserved E2 H170 is in position to form a hydrogen bond with the underlying E1 S57. Here we experimentally tested the role of this interaction in regulating dimer dissociation in mature and immature virus. Alanine substitutions of E1 S57 and E2 H170 destabilized the heterodimer and produced a higher pH threshold for exposure of the E1 fusion loop and for fusion of the immature virus. E1 S57K or S57D mutations were lethal and caused transport and assembly defects that were partially abrogated by neutralization of the exocytic pathway. The lethal phenotype of E1 S57K was rescued by second-site mutations at E2 H170/M171. Together, our results define a key role for the E1 S57-E2 H170 interaction in dimer stability and the pH dependence of fusion and provide evidence for stepwise dissociation of the E2-E1 dimer at low pH.
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A specific domain of the Chikungunya virus E2 protein regulates particle formation in human cells: implications for alphavirus vaccine design. J Virol 2012; 86:8879-83. [PMID: 22647698 DOI: 10.1128/jvi.00370-12] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023] Open
Abstract
Virus-like particles (VLPs) can be generated from Chikungunya virus (CHIKV), but different strains yield variable quantities of particles. Here, we define the genetic basis for these differences and show that amino acid 234 in E2 substantially affects VLP production. This site is located within the acid-sensitive region (ASR) known to initiate a major conformational change in E1/E2. Selected other mutations in the ASR, or changes in pH, also increased VLP yield. These results demonstrate that the ASR of E2 plays an important role in regulating particle generation.
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12
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Cheng G, Liu L, Wang P, Zhang Y, Zhao YO, Colpitts TM, Feitosa F, Anderson JF, Fikrig E. An in vivo transfection approach elucidates a role for Aedes aegypti thioester-containing proteins in flaviviral infection. PLoS One 2011; 6:e22786. [PMID: 21818390 PMCID: PMC3144946 DOI: 10.1371/journal.pone.0022786] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2011] [Accepted: 07/04/2011] [Indexed: 02/07/2023] Open
Abstract
Mosquitoes transmit pathogens that cause infectious diseases of global importance. Techniques to easily introduce genes into mosquitoes, however, limit investigations of the interaction between microbes and their arthropod vectors. We now show that a cationic liposome significantly enhances delivery and expression of plasmid DNA in Aedes aegypti and Anopheles gambiae mosquitoes. We then introduced the genes for Ae. aegypti thioester-containing proteins (AeTEPs), which are involved in the control of flaviviral infection, into mosquitoes using this technique. In vivo transfection of AeTEP-1 into Ae. aegypti significantly reduced dengue virus infection, suggesting that the approach can further our understanding of pathogen-mosquito interactions.
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Affiliation(s)
- Gong Cheng
- Section of Infectious Diseases, Department of Internal Medicine, Yale University School of Medicine, New Haven, Connecticut, United States of America
| | - Lei Liu
- Section of Infectious Diseases, Department of Internal Medicine, Yale University School of Medicine, New Haven, Connecticut, United States of America
| | - Penghua Wang
- Section of Infectious Diseases, Department of Internal Medicine, Yale University School of Medicine, New Haven, Connecticut, United States of America
| | - Yue Zhang
- Section of Infectious Diseases, Department of Internal Medicine, Yale University School of Medicine, New Haven, Connecticut, United States of America
| | - Yang O. Zhao
- Section of Infectious Diseases, Department of Internal Medicine, Yale University School of Medicine, New Haven, Connecticut, United States of America
| | - Tonya M. Colpitts
- Section of Infectious Diseases, Department of Internal Medicine, Yale University School of Medicine, New Haven, Connecticut, United States of America
| | - Fabiana Feitosa
- Section of Infectious Diseases, Department of Internal Medicine, Yale University School of Medicine, New Haven, Connecticut, United States of America
| | - John F. Anderson
- Department of Entomology, Connecticut Agricultural Experiment Station, New Haven, Connecticut, United States of America
| | - Erol Fikrig
- Section of Infectious Diseases, Department of Internal Medicine, Yale University School of Medicine, New Haven, Connecticut, United States of America
- Howard Hughes Medical Institute, Chevy Chase, Maryland, United States of America
- * E-mail:
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Abstract
The study of enveloped animal viruses has greatly advanced our understanding of the general properties of membrane fusion and of the specific pathways that viruses use to infect the host cell. The membrane fusion proteins of the alphaviruses and flaviviruses have many similarities in structure and function. As reviewed here, alphaviruses use receptor-mediated endocytic uptake and low pH-triggered membrane fusion to deliver their RNA genomes into the cytoplasm. Recent advances in understanding the biochemistry and structure of the alphavirus membrane fusion protein provide a clearer picture of this fusion reaction, including the protein’s conformational changes during fusion and the identification of key domains. These insights into the alphavirus fusion mechanism suggest new areas for experimental investigation and potential inhibitor strategies for anti-viral therapy.
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Affiliation(s)
- Margaret Kielian
- Author to whom correspondence should be addressed; E-Mail: ; Tel.: +1-718-430-3638; Fax: +1-718-430-8574
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14
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Role of conserved histidine residues in the low-pH dependence of the Semliki Forest virus fusion protein. J Virol 2009; 83:4670-7. [PMID: 19244325 DOI: 10.1128/jvi.02646-08] [Citation(s) in RCA: 58] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
A wide variety of enveloped viruses infects cells by taking advantage of the low pH in the endocytic pathway to trigger virus-membrane fusion. For alphaviruses such as Semliki Forest virus (SFV), acidic pH initiates a series of conformational changes in the heterodimeric virus envelope proteins E1 and E2. Low pH dissociates the E2/E1 dimer, releasing the membrane fusion protein E1. E1 inserts into the target membrane and refolds to a trimeric hairpin conformation, thus driving the fusion reaction. The means by which E1 senses and responds to low pH is unclear, and protonation of conserved E1 histidine residues has been proposed as a possible mechanism. We tested the role of four conserved histidines by mutagenesis of the wild-type (wt) SFV infectious clone to create virus mutants with E1 H3A, H125A, H331A, and H331A/H333A mutations. The H125A, H331A, and H331A/H333A mutants had growth properties similar to those of wt SFV and showed modest change or no change in the pH dependence of virus-membrane fusion. By contrast, the E1 H3A mutation produced impaired virus growth and a markedly more acidic pH requirement for virus-membrane fusion. The dissociation of the H3A heterodimer and the membrane insertion of the mutant E1 protein were comparable to those of the wt in efficiency and pH dependence. However, the formation of the H3A homotrimer required a much lower pH and showed reduced efficiency. Together, these results and the location of H3 suggest that this residue acts to regulate the low-pH-dependent refolding of E1 during membrane fusion.
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15
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Taylor GM, Hanson PI, Kielian M. Ubiquitin depletion and dominant-negative VPS4 inhibit rhabdovirus budding without affecting alphavirus budding. J Virol 2007; 81:13631-9. [PMID: 17913808 PMCID: PMC2168838 DOI: 10.1128/jvi.01688-07] [Citation(s) in RCA: 64] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2007] [Accepted: 09/21/2007] [Indexed: 12/22/2022] Open
Abstract
The budding reactions of a number of enveloped viruses use the cellular machinery involved in the formation of the luminal vesicles of endosomal multivesicular bodies (MVB). Budding of these viruses is dependent on the presence of specific late-domain motifs in membrane-associated viral proteins. Such budding reactions usually involve ubiquitin and are blocked by expression of an ATPase-deficient form of VPS4, a cellular AAA+ ATPase believed to be required late in the MVB pathway for the disassembly/release of the MVB machinery. Here we examined the role of the MVB pathway in the budding of the late-domain-containing rhabdovirus vesicular stomatitis virus (VSV) and the alphavirus Semliki Forest virus (SFV). We tested early and late steps in the MVB pathway by depleting ubiquitin with the proteasome inhibitor MG-132 and by using cell lines inducibly expressing VPS4A or VPS4B protein. As previously shown, VSV budding was strongly dependent on ubiquitin. In contrast to the findings of previous studies with VPS4A, expression of ATPase-deficient mutants of either VPS4A or VPS4B inhibited VSV budding. Inhibition by VPS4 required the presence of the PPPY late domain on the VSV matrix protein and resulted in the accumulation of nonreleased VSV particles at the plasma membrane. In contrast, SFV budding was independent of both ubiquitin and the activity of VPS4, perhaps reflecting the important role of the highly organized envelope protein lattice during alphavirus budding.
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Affiliation(s)
- Gwen M Taylor
- Department of Cell Biology, Albert Einstein College of Medicine, Bronx, New York 10461, USA
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16
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Liao M, Kielian M. Functions of the stem region of the Semliki Forest virus fusion protein during virus fusion and assembly. J Virol 2006; 80:11362-9. [PMID: 16971447 PMCID: PMC1642169 DOI: 10.1128/jvi.01679-06] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
Membrane fusion of the alphaviruses is mediated by the E1 protein, a class II virus membrane fusion protein. During fusion, E1 dissociates from its heterodimer interaction with the E2 protein and forms a target membrane-inserted E1 homotrimer. The structure of the homotrimer is that of a trimeric hairpin in which E1 domain III and the stem region fold back toward the target membrane-inserted fusion peptide loop. The E1 stem region has a strictly conserved length and several highly conserved residues, suggesting the possibility of specific stem interactions along the trimer core and an important role in driving membrane fusion. Mutagenesis studies of the alphavirus Semliki Forest virus (SFV) here demonstrated that there was a strong requirement for the E1 stem in virus assembly and budding, probably reflecting its importance in lateral interactions of the envelope proteins. Surprisingly, however, neither the conserved length nor any specific residues of the stem were required for membrane fusion. Although the highest fusion activity was observed with wild-type E1, efficient fusion was mediated by stem mutants containing a variety of substitutions or deletions. A minimal stem length was required but could be conferred by a series of alanine residues. The lack of a specific stem sequence requirement during SFV fusion suggests that the interaction of domain III with the trimer core can provide sufficient driving force to mediate membrane merger.
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Affiliation(s)
- Maofu Liao
- Department of Cell Biology, Albert Einstein College of Medicine, 1300 Morris Park Ave., Bronx, NY 10461, USA
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17
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Zaitseva E, Mittal A, Griffin DE, Chernomordik LV. Class II fusion protein of alphaviruses drives membrane fusion through the same pathway as class I proteins. ACTA ACUST UNITED AC 2005; 169:167-77. [PMID: 15809312 PMCID: PMC2171914 DOI: 10.1083/jcb.200412059] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/04/2022]
Abstract
Viral fusion proteins of classes I and II differ radically in their initial structures but refold toward similar conformations upon activation. Do fusion pathways mediated by alphavirus E1 and influenza virus hemagglutinin (HA) that exemplify classes II and I differ to reflect the difference in their initial conformations, or concur to reflect the similarity in the final conformations? Here, we dissected the pathway of low pH–triggered E1-mediated cell–cell fusion by reducing the numbers of activated E1 proteins and by blocking different fusion stages with specific inhibitors. The discovered progression from transient hemifusion to small, and then expanding, fusion pores upon an increase in the number of activated fusion proteins parallels that established for HA-mediated fusion. We conclude that proteins as different as E1 and HA drive fusion through strikingly similar membrane intermediates, with the most energy-intensive stages following rather than preceding hemifusion. We propose that fusion reactions catalyzed by all proteins of both classes follow a similar pathway.
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Affiliation(s)
- Elena Zaitseva
- Section on Membrane Biology, Laboratory of Cellular and Molecular Biophysics, National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892, USA
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18
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Chanel-Vos C, Kielian M. A conserved histidine in the ij loop of the Semliki Forest virus E1 protein plays an important role in membrane fusion. J Virol 2004; 78:13543-52. [PMID: 15564465 PMCID: PMC533937 DOI: 10.1128/jvi.78.24.13543-13552.2004] [Citation(s) in RCA: 54] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
The enveloped alphavirus Semliki Forest virus (SFV) infects cells via a low pH-triggered membrane fusion reaction mediated by the E1 protein. E1 is a class II fusion protein that contains the hydrophobic fusion peptide loop and converts to a stable homotrimer during the fusion reaction. Intriguingly, the fusion loop is closely associated with a loop connecting the i and j beta-strands. This ij loop plays a role in the cholesterol dependence of membrane fusion and is specifically susceptible to proteolysis in the protease-resistant E1 homotrimer. The SFV ij loop contains a histidine residue at position 230. Sequence comparisons revealed that an analogous histidine is completely conserved in all alphavirus and flavivirus fusion proteins. An E1 H230A mutant was constructed using the SFV infectious clone. Although cells infected with H230A RNA produced virus particles, these virions were completely noninfectious and were blocked in both cell-cell fusion and lipid mixing assays. The H230A virions efficiently bound to cell surface receptors and responded to low pH by undergoing acid-dependent conformational changes including dissociation of the E1/E2 dimer, exposure of the fusion loop, association with target liposomes, exposure of acid-conformation-specific epitopes, and formation of the stable E1 homotrimer. Studies with a soluble fragment of E1 showed that the mutant protein was defective in lipid-dependent conformational changes. Our results indicate that the E1 ij loop and the conserved H230 residue play a critical role in alphavirus-membrane fusion and suggest the presence of a previously undescribed late intermediate in the fusion reaction.
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Affiliation(s)
- Chantal Chanel-Vos
- Department of Cell Biology, Albert Einstein College of Medicine, 1300 Morris Park Ave., Bronx, NY 10461, USA
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19
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Zhang X, Kielian M. Mutations that promote furin-independent growth of Semliki Forest virus affect p62-E1 interactions and membrane fusion. Virology 2004; 327:287-96. [PMID: 15351216 DOI: 10.1016/j.virol.2004.06.037] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2004] [Accepted: 06/24/2004] [Indexed: 11/17/2022]
Abstract
The enveloped alphavirus Semliki Forest virus (SFV) infects cells via a low pH-triggered membrane fusion reaction mediated by the E1 protein. E1's fusion activity is regulated by its heterodimeric interaction with a companion membrane protein E2. Mature E2 protein is generated by furin processing of the precursor p62. Processing destabilizes the heterodimer, allowing dissociation at acidic pH, E1 conformational changes, and membrane fusion. We used a furin-deficient cell line, FD11, to select for SFV mutants that show increased growth in the absence of p62 processing. We isolated and characterized 7 such pci mutants (p62 cleavage independent), which retained the parental furin cleavage site but showed significant increases in their ability to carry out membrane fusion in the p62 form. Sequence analysis of the pci mutants identified mutations primarily on the E2 protein, and suggested sites important in the interaction of p62 with E1 and the regulation of fusion.
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Affiliation(s)
- Xinyong Zhang
- Department of Cell Biology, Albert Einstein College of Medicine, Bronx, NY 10461, USA
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20
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Abstract
The alphavirus Semliki Forest virus (SFV) infects cells via a low-pH-dependent membrane fusion reaction mediated by the E1 envelope protein. Fusion is regulated by the interaction of E1 with the receptor-binding protein E2. E2 is synthesized as a precursor termed "p62," which forms a stable heterodimer with E1 and is processed late in the secretory pathway by a cellular furin-like protease. Once processing to E2 occurs, the E1/E2 heterodimer is destabilized so that it is more readily dissociated by exposure to low pH, allowing fusion and infection. We have used FD11 cells, a furin-deficient CHO cell line, to characterize the processing of p62 and its role in the control of virus fusion and infection. p62 was not cleaved in FD11 cells and cleavage was restored in FD11 cell transfectants expressing human furin. Studies of unprocessed virus produced in FD11 cells (wt/p62) demonstrated that the p62 protein was efficiently cleaved by purified furin in vitro, without requiring prior exposure to low pH. wt/p62 virus particles were also processed during their endocytic uptake in furin-containing cells, resulting in more efficient virus infection. wt/p62 virus was compared with mutant L, in which p62 cleavage was blocked by mutation of the furin-recognition motif. wt/p62 and mutant L had similar fusion properties, requiring a much lower pH than control virus to trigger fusion and fusogenic E1 conformational changes. However, the in vivo infectivity of mutant L was more strongly inhibited than that of wt/p62, due to additional effects of the mutation on virus-cell binding.
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Affiliation(s)
- Xinyong Zhang
- Department of Cell Biology, Albert Einstein College of Medicine, Bronx, New York 10461, USA
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21
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Samsonov AV, Chatterjee PK, Razinkov VI, Eng CH, Kielian M, Cohen FS. Effects of membrane potential and sphingolipid structures on fusion of Semliki Forest virus. J Virol 2002; 76:12691-702. [PMID: 12438595 PMCID: PMC136663 DOI: 10.1128/jvi.76.24.12691-12702.2002] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Cells expressing the E1 and E2 envelope proteins of Semliki Forest virus (SFV) were fused to voltage-clamped planar lipid bilayer membranes at low pH. Formation and evolution of fusion pores were electrically monitored by capacitance measurements, and membrane continuity was tracked by video fluorescence microscopy by including rhodamine-phosphatidylethanolamine in the bilayer. Fusion occurred without leakage for a negative potential applied to the trans side of the planar membrane. When a positive potential was applied, leakage was severe, obscuring the observation of any fusion. E1-mediated cell-cell fusion occurred without leakage for negative intracellular potentials but with substantial leakage for zero membrane potential. Thus, negative membrane potentials are generally required for nonleaky fusion. With planar bilayers as the target, the first fusion pore that formed almost always enlarged; pore flickering was a rare event. Similar to other target membranes, fusion required cholesterol and sphingolipids in the planar membrane. Sphingosine did not support fusion, but both ceramide, with even a minimal acyl chain (C(2)-ceramide), and lysosphingomyelin (lyso-SM) promoted fusion with the same kinetics. Thus, unrelated modifications to different parts of sphingosine yielded sphingolipids that supported fusion to the same degree. Fusion studies of pyrene-labeled SFV with cholesterol-containing liposomes showed that C(2)-ceramide supported fusion while lyso-SM did not, apparently due to its positive curvature effects. A model is proposed in which the hydroxyls of C-1 and C-3 as well as N of C-2 of the sphingosine backbone must orient so as to form multiple hydrogen bonds to amino acids of SFV E1 for fusion to proceed.
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Affiliation(s)
- Andrey V Samsonov
- Department of Molecular Biophysics and Physiology, Rush Medical College, 1653 W. Congress Parkway, Chicago, IL 60612, USA
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22
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Chatterjee PK, Eng CH, Kielian M. Novel mutations that control the sphingolipid and cholesterol dependence of the Semliki Forest virus fusion protein. J Virol 2002; 76:12712-22. [PMID: 12438597 PMCID: PMC136714 DOI: 10.1128/jvi.76.24.12712-12722.2002] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The enveloped alphavirus Semliki Forest virus (SFV) infects cells via a membrane fusion reaction mediated by the E1 membrane protein. Efficient SFV-membrane fusion requires the presence of cholesterol and sphingolipid in the target membrane. Here we report on two mutants, srf-4 and srf-5, selected for growth in cholesterol-depleted cells. Like the previously isolated srf-3 mutant (E1 proline 226 to serine), the phenotypes of the srf-4 and srf-5 mutants were conferred by single-amino-acid changes in the E1 protein: leucine 44 to phenylalanine and valine 178 to alanine, respectively. Like srf-3, srf-4 and srf-5 show striking increases in the cholesterol independence of growth, infection, membrane fusion, and exit. Unexpectedly, and unlike srf-3, srf-4 and srf-5 showed highly efficient fusion with sphingolipid-free membranes in both lipid- and content-mixing assays. Both srf-4 and srf-5 formed E1 homotrimers of decreased stability compared to the homotrimers of the wild type and the srf-3 mutant. All three srf mutations lie in the same domain of E1, but the srf-4 and srf-5 mutations are spatially separated from srf-3. When expressed together, the three mutations could interact to produce increased sterol independence and to cause temperature-sensitive E1 transport. Thus, the srf-4 and srf-5 mutations identify novel regions of E1 that are distinct from the fusion peptide and srf-3 region and modulate the requirements for both sphingolipid and cholesterol in virus-membrane fusion.
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Affiliation(s)
- Prodyot K Chatterjee
- Department of Cell Biology, Albert Einstein College of Medicine, 1300 Morris Park Avenue, Bronx, NY 10461, USA
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