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Hirch T, Brander N, Schenk F, Pöllmann SJ, Reichenbach J, Schubert R, Modlich U. Expression of a large coding sequence: Gene therapy vectors for Ataxia Telangiectasia. Sci Rep 2023; 13:19386. [PMID: 37938627 PMCID: PMC10632516 DOI: 10.1038/s41598-023-46332-4] [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: 07/26/2023] [Accepted: 10/31/2023] [Indexed: 11/09/2023] Open
Abstract
Ataxia telangiectasia is a monogenetic disorder caused by mutations in the ATM gene. Its encoded protein kinase ATM plays a fundamental role in DNA repair of double strand breaks (DSBs). Impaired function of this kinase leads to a multisystemic disorder including immunodeficiency, progressive cerebellar degeneration, radiation sensitivity, dilated blood vessels, premature aging and a predisposition to cancer. Since allogenic hematopoietic stem cell (HSC) transplantation improved disease outcome, gene therapy based on autologous HSCs is an alternative promising concept. However, due to the large cDNA of ATM (9.2 kb), efficient packaging of retroviral particles and sufficient transduction of HSCs remains challenging.We generated lentiviral, gammaretroviral and foamy viral vectors with a GFP.F2A.Atm fusion or a GFP transgene and systematically compared transduction efficiencies. Vector titers dropped with increasing transgene size, but despite their described limited packaging capacity, we were able to produce lentiviral and gammaretroviral particles. The reduction in titers could not be explained by impaired packaging of the viral genomes, but the main differences occurred after transduction. Finally, after transduction of Atm-deficient (ATM-KO) murine fibroblasts with the lentiviral vector expressing Atm, we could show the expression of ATM protein which phosphorylated its downstream substrates (pKap1 and p-p53).
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Affiliation(s)
- Tanja Hirch
- Division of Veterinary Medicine, RG Gene Modification in Stem Cells, Paul-Ehrlich-Institute, Langen, Germany
| | - Nadine Brander
- Division of Veterinary Medicine, RG Gene Modification in Stem Cells, Paul-Ehrlich-Institute, Langen, Germany
| | - Franziska Schenk
- Division of Veterinary Medicine, RG Gene Modification in Stem Cells, Paul-Ehrlich-Institute, Langen, Germany
| | - Simon J Pöllmann
- Division of Veterinary Medicine, RG Gene Modification in Stem Cells, Paul-Ehrlich-Institute, Langen, Germany
- Department of Gene and Cell Therapy, Institute for Regenerative Medicine - IREM, University of Zurich, Schlieren, Switzerland
| | - Janine Reichenbach
- Department of Gene and Cell Therapy, Institute for Regenerative Medicine - IREM, University of Zurich, Schlieren, Switzerland
- Deptartment of Somatic Gene Therapy, University Children's Hospital Zurich, Zurich, Switzerland
- Competence Center for Applied Biotechnology and Molecular Medicine (CABMM), University of Zurich, Zurich, Switzerland
| | - Ralf Schubert
- Department for Children and Adolescents, University Hospital Frankfurt, Goethe University, Frankfurt, Germany
| | - Ute Modlich
- Division of Veterinary Medicine, RG Gene Modification in Stem Cells, Paul-Ehrlich-Institute, Langen, Germany.
- Department of Gene and Cell Therapy, Institute for Regenerative Medicine - IREM, University of Zurich, Schlieren, Switzerland.
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Le SJ, Xin GY, Wu WC, Shi M. Genetic Diversity and Evolution of Viruses Infecting Felis catus: A Global Perspective. Viruses 2023; 15:1338. [PMID: 37376637 DOI: 10.3390/v15061338] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2023] [Revised: 05/27/2023] [Accepted: 05/29/2023] [Indexed: 06/29/2023] Open
Abstract
Cats harbor many important viral pathogens, and the knowledge of their diversity has been greatly expanded thanks to increasingly popular molecular sequencing techniques. While the diversity is mostly described in numerous regionally defined studies, there lacks a global overview of the diversity for the majority of cat viruses, and therefore our understanding of the evolution and epidemiology of these viruses was generally inadequate. In this study, we analyzed 12,377 genetic sequences from 25 cat virus species and conducted comprehensive phylodynamic analyses. It revealed, for the first time, the global diversity for all cat viruses known to date, taking into account highly virulent strains and vaccine strains. From there, we further characterized and compared the geographic expansion patterns, temporal dynamics and recombination frequencies of these viruses. While respiratory pathogens such as feline calicivirus showed some degree of geographical panmixes, the other viral species are more geographically defined. Furthermore, recombination rates were much higher in feline parvovirus, feline coronavirus, feline calicivirus and feline foamy virus than the other feline virus species. Collectively, our findings deepen the understanding of the evolutionary and epidemiological features of cat viruses, which in turn provide important insight into the prevention and control of cat pathogens.
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Affiliation(s)
- Shi-Jia Le
- State Key Laboratory for Biocontrol, School of Medicine, Shenzhen Campus of Sun Yat-sen University, Sun Yat-sen University, Shenzhen 518107, China
| | - Gen-Yang Xin
- State Key Laboratory for Biocontrol, School of Medicine, Shenzhen Campus of Sun Yat-sen University, Sun Yat-sen University, Shenzhen 518107, China
| | - Wei-Chen Wu
- State Key Laboratory for Biocontrol, School of Medicine, Shenzhen Campus of Sun Yat-sen University, Sun Yat-sen University, Shenzhen 518107, China
| | - Mang Shi
- State Key Laboratory for Biocontrol, School of Medicine, Shenzhen Campus of Sun Yat-sen University, Sun Yat-sen University, Shenzhen 518107, China
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AbuEed L, Makundi I, Miyake A, Kawasaki J, Minoura C, Koshida Y, Nishigaki K. Feline Foamy Virus Transmission in Tsushima Leopard Cats (Prionailurus bengalensis euptilurus) on Tsushima Island, Japan. Viruses 2023; 15:v15040835. [PMID: 37112816 PMCID: PMC10146696 DOI: 10.3390/v15040835] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2023] [Revised: 03/14/2023] [Accepted: 03/22/2023] [Indexed: 03/29/2023] Open
Abstract
Tsushima leopard cats (TLC; Prionailurus bengalensis euptilurus) only inhabit Tsushima Island, Nagasaki, Japan and are critically endangered and threatened by infectious diseases. The feline foamy virus (FFV) is widely endemic in domestic cats. Therefore, its transmission from domestic cats to TLCs may threaten the TLC population. Thus, this study aimed to assess the possibility that domestic cats could transmit FFV to TLCs. Eighty-nine TLC samples were screened, and FFV was identified in seven (7.86%). To assess the FFV infection status of domestic cats, 199 domestic cats were screened; 14.07% were infected. The phylogenetic analysis revealed that the FFV partial sequence from domestic cats and TLC sequences clustered in one clade, suggesting that the two populations share the same strain. The statistical data minimally supported the association between increased infection rate and sex (p = 0.28), indicating that FFV transmission is not sex dependent. In domestic cats, a significant difference was observed in FFV detection in feline immunodeficiency virus (p = 0.002) and gammaherpesvirus1 infection statuses (p = 0.0001) but not in feline leukemia virus infection status (p = 0.21). Monitoring FFV infection in domestic cats and TLC populations is highly recommended as part of TLC surveillance and management strategies.
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Smith RH, Bloomer H, Fink D, Keyvanfar K, Nasimuzzaman M, Sancheznieto F, Dutta R, Guenther Bui K, Alvarado LJ, Bauer TR, Hickstein DD, Russell DW, Malik P, van der Loo JC, Highfill SL, Kuhns DB, Pirooznia M, Larochelle A. Preclinical Evaluation of Foamy Virus Vector-Mediated Gene Addition in Human Hematopoietic Stem/Progenitor Cells for Correction of Leukocyte Adhesion Deficiency Type 1. Hum Gene Ther 2022; 33:1293-1304. [PMID: 36094106 PMCID: PMC9808799 DOI: 10.1089/hum.2022.065] [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: 03/16/2022] [Accepted: 08/23/2022] [Indexed: 01/13/2023] Open
Abstract
Ex vivo gene therapy procedures targeting hematopoietic stem and progenitor cells (HSPCs) predominantly utilize lentivirus-based vectors for gene transfer. We provide the first pre-clinical evidence of the therapeutic utility of a foamy virus vector (FVV) for the genetic correction of human leukocyte adhesion deficiency type 1 (LAD-1), an inherited primary immunodeficiency resulting from mutation of the β2 integrin common chain, CD18. CD34+ HSPCs isolated from a severely affected LAD-1 patient were transduced under a current good manufacturing practice-compatible protocol with FVV harboring a therapeutic CD18 transgene. LAD-1-associated cellular chemotactic defects were ameliorated in transgene-positive, myeloid-differentiated LAD-1 cells assayed in response to a strong neutrophil chemoattractant in vitro. Xenotransplantation of vector-transduced LAD-1 HSPCs in immunodeficient (NSG) mice resulted in long-term (∼5 months) human cell engraftment within murine bone marrow. Moreover, engrafted LAD-1 myeloid cells displayed in vivo levels of transgene marking previously reported to ameliorate the LAD-1 phenotype in a large animal model of the disease. Vector insertion site analysis revealed a favorable vector integration profile with no overt evidence of genotoxicity. These results coupled with the unique biological features of wild-type foamy virus support the development of FVVs for ex vivo gene therapy of LAD-1.
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Affiliation(s)
- Richard H. Smith
- Cellular and Molecular Therapeutics Branch, National Heart, Lung, Blood Institute, National Institutes of Health, Bethesda, Maryland, USA
| | - Hanan Bloomer
- Cellular and Molecular Therapeutics Branch, National Heart, Lung, Blood Institute, National Institutes of Health, Bethesda, Maryland, USA
| | - Danielle Fink
- Neutrophil Monitoring Lab, Leidos Biomedical Research, Inc., Frederick National Laboratory for Cancer Research, Frederick, Maryland, USA
| | - Keyvan Keyvanfar
- Cellular and Molecular Therapeutics Branch, National Heart, Lung, Blood Institute, National Institutes of Health, Bethesda, Maryland, USA
| | - Md Nasimuzzaman
- Division of Experimental Hematology and Cancer Biology, Cincinnati Children's Hospital Medical Center, Cincinnati, Ohio, USA
| | - Fátima Sancheznieto
- Cellular and Molecular Therapeutics Branch, National Heart, Lung, Blood Institute, National Institutes of Health, Bethesda, Maryland, USA
| | - Roop Dutta
- Cellular and Molecular Therapeutics Branch, National Heart, Lung, Blood Institute, National Institutes of Health, Bethesda, Maryland, USA
| | - Kacey Guenther Bui
- Cellular and Molecular Therapeutics Branch, National Heart, Lung, Blood Institute, National Institutes of Health, Bethesda, Maryland, USA
| | - Luigi J. Alvarado
- Cellular and Molecular Therapeutics Branch, National Heart, Lung, Blood Institute, National Institutes of Health, Bethesda, Maryland, USA
| | - Thomas R. Bauer
- Immune Deficiency-Cellular Therapy Program, National Cancer Institute, National Institutes of Health, Bethesda, Maryland, USA
| | - Dennis D. Hickstein
- Immune Deficiency-Cellular Therapy Program, National Cancer Institute, National Institutes of Health, Bethesda, Maryland, USA
| | - David W. Russell
- Department of Medicine, University of Washington, Seattle, Washington, USA
| | - Punam Malik
- Division of Experimental Hematology and Cancer Biology, Cincinnati Children's Hospital Medical Center, Cincinnati, Ohio, USA
| | - Johannes C.M. van der Loo
- Division of Experimental Hematology and Cancer Biology, Cincinnati Children's Hospital Medical Center, Cincinnati, Ohio, USA
| | - Steven L. Highfill
- Center for Cellular Engineering, Department of Transfusion Medicine, Clinical Center, National Institutes of Health, Bethesda, Maryland, USA
| | - Douglas B. Kuhns
- Neutrophil Monitoring Lab, Leidos Biomedical Research, Inc., Frederick National Laboratory for Cancer Research, Frederick, Maryland, USA
| | - Mehdi Pirooznia
- Laboratory of Bioinformatics and Computational Biology, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, Maryland, USA
| | - Andre Larochelle
- Cellular and Molecular Therapeutics Branch, National Heart, Lung, Blood Institute, National Institutes of Health, Bethesda, Maryland, USA
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The Unique, the Known, and the Unknown of Spumaretrovirus Assembly. Viruses 2021; 13:v13010105. [PMID: 33451128 PMCID: PMC7828637 DOI: 10.3390/v13010105] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2020] [Revised: 01/08/2021] [Accepted: 01/10/2021] [Indexed: 12/22/2022] Open
Abstract
Within the family of Retroviridae, foamy viruses (FVs) are unique and unconventional with respect to many aspects in their molecular biology, including assembly and release of enveloped viral particles. Both components of the minimal assembly and release machinery, Gag and Env, display significant differences in their molecular structures and functions compared to the other retroviruses. This led to the placement of FVs into a separate subfamily, the Spumaretrovirinae. Here, we describe the molecular differences in FV Gag and Env, as well as Pol, which is translated as a separate protein and not in an orthoretroviral manner as a Gag-Pol fusion protein. This feature further complicates FV assembly since a specialized Pol encapsidation strategy via a tripartite Gag-genome–Pol complex is used. We try to relate the different features and specific interaction patterns of the FV Gag, Pol, and Env proteins in order to develop a comprehensive and dynamic picture of particle assembly and release, but also other features that are indirectly affected. Since FVs are at the root of the retrovirus tree, we aim at dissecting the unique/specialized features from those shared among the Spuma- and Orthoretrovirinae. Such analyses may shed light on the evolution and characteristics of virus envelopment since related viruses within the Ortervirales, for instance LTR retrotransposons, are characterized by different levels of envelopment, thus affecting the capacity for intercellular transmission.
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Koç BT, Oğuzoğlu TÇ. First report on the prevalence and genetic relatedness of Feline Foamy Virus (FFV) from Turkish domestic cats. Virus Res 2019; 274:197768. [PMID: 31562905 DOI: 10.1016/j.virusres.2019.197768] [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] [Received: 03/15/2019] [Revised: 09/19/2019] [Accepted: 09/23/2019] [Indexed: 10/25/2022]
Abstract
Feline Foamy Virus (FFV) is an important retroviral agent affecting domestic cats in Turkey that has been studied less intensively than Feline Immunodeficiency Virus (FIV) and Feline Leukemia Virus (FeLV). Accordingly, we aimed to investigate the presence and prevalence of FFV among domestic cats by molecular techniques. PCR was used to amplify the gag-pol gene overlap in order to detect the presence of FFV. The gene encoding bet, an important accessory gene, was also characterized. Molecular characteristics were analyzed and phylogenetic trees were constructed. We determined the positivity rate as 10% in all samples (20/200) based on the gag-pol test. The phylogenetic analysis indicated that the Turkish FFV sequences form a separate cluster among other isolates in the constructed maximum likelihood (ML) tree. bet-based products were obtained for two samples (1%; 2/200) that were also positive for gag-pol. These bet gene sequences confirm the presence of a separate cluster for the Turkish FFV isolates. The results suggest that FFV is prevalent and widespread in Turkish domestic cats. Additionally, these new FFV sequences represent the first FFV sequences from Turkey to be submitted to GenBank. This study paves the way for studies on the pathogenicity of FFV.
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Affiliation(s)
- B Taylan Koç
- Aydın Adnan Menderes University, Faculty of Veterinary Medicine, Department of Virology, Section "C", Isikli-Efeler, 09016, Aydin, Turkey.
| | - T Çiğdem Oğuzoğlu
- Ankara University, Faculty of Veterinary Medicine, Department of Virology, 06110, Dışkapı, Ankara, Turkey
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Kechejian S, Dannemiller N, Kraberger S, Ledesma Feliciano C, Löchelt M, Carver S, VandeWoude S. Feline foamy virus seroprevalence and demographic risk factors in stray domestic cat populations in Colorado, Southern California and Florida, USA. JFMS Open Rep 2019; 5:2055116919873736. [PMID: 31555460 PMCID: PMC6747863 DOI: 10.1177/2055116919873736] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023] Open
Abstract
Objectives Our study aim was to document the seroprevalence and associated risk factors of feline foamy virus (FFV) infection in domestic cat populations presented to animal shelters located in Southern California, Colorado and Florida, USA. Methods We used a glutathione S-transferase capture ELISA targeting the FFV Gag antigen to screen domestic cat serum collected from cats with unknown owners at eight different animal shelters from Colorado (n = 105, three shelters), Southern California (n = 172, three shelters) and Florida (n = 31, two shelters). χ2 statistics determined location effect on seroprevalence. Bayesian generalized linear models were used to explore age and sex as potential risk factors for infection. Results FFV seroprevalence was 64.0% across all locations. Seroprevalence by location was as follows: Southern California 75.0%, Colorado 52.4% and Florida 41.9%, with Southern California’s seroprevalence being significantly higher. Age had a significant effect on model fit for all locations, with adults having a higher probability of being infected. In Colorado, sex also had a significant effect on model fit, with males having a higher probability of being infected. Conclusions and relevance We have documented that FFV is extremely common in stray domestic cat populations across varied geographic and ecological niches throughout the USA. Adult cats are at a higher FFV infection risk than young cats. FFV has been associated with a higher risk of other retroviral infections and has been implicated in several chronic diseases of cats. Additional epidemiological and clinical studies are warranted to investigate the potential impacts of FFV on domestic cat health.
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Affiliation(s)
- Sarah Kechejian
- Department of Microbiology, Immunology, and Pathology, College of Veterinary Medicine and Biomedical Sciences, Colorado State University, Fort Collins, CO, USA
| | - Nick Dannemiller
- Department of Microbiology, Immunology, and Pathology, College of Veterinary Medicine and Biomedical Sciences, Colorado State University, Fort Collins, CO, USA
| | - Simona Kraberger
- The Biodesign Center for Fundamental and Applied Microbiomics, Center for Evolution and Medicine, School of Life Sciences, Arizona State University, Tempe, AZ, USA
| | - Carmen Ledesma Feliciano
- Division of Infectious Diseases, University of Colorado Anschutz Medical Campus, Aurora, CO, USA
| | - Martin Löchelt
- Department of Molecular Diagnostics of Oncogenic Infections, Research Program Infection, Inflammation and Cancer, German Cancer Research Center (Deutsches Krebsforschungszentrum Heidelberg, DKFZ), Heidelberg, Germany
| | - Scott Carver
- School of Biological Sciences, University of Tasmania, Sandy Bay, Tasmania, Australia
| | - Sue VandeWoude
- Department of Microbiology, Immunology, and Pathology, College of Veterinary Medicine and Biomedical Sciences, Colorado State University, Fort Collins, CO, USA
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Clinical and Molecular Features of Feline Foamy Virus and Feline Leukemia Virus Co-Infection in Naturally-Infected Cats. Viruses 2018; 10:v10120702. [PMID: 30544924 PMCID: PMC6315984 DOI: 10.3390/v10120702] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2018] [Revised: 12/06/2018] [Accepted: 12/07/2018] [Indexed: 11/17/2022] Open
Abstract
Feline foamy virus (FFV) and feline leukemia virus (FeLV) belong to the Retroviridae family. While disease has not been reported for FFV infection, FeLV infection can cause anemia and immunosuppression (progressive infection). Co-infection with FFV/FeLV allows evaluation of the pathogenic potential and epidemiology of FFV infection in cats with FeLV pathology. Blood and buccal swab samples from 81 cats were collected in Rio de Janeiro. Plasma was serologically tested for FeLV. DNA extracted from peripheral blood mononuclear cells and buccal swabs was used to PCR detect FFV and FeLV. A qPCR was developed to detect and measure FFV proviral loads (pVLs) in cats. FeLV qPCR was performed using previous methods. The median log10 pVL of FFV mono-infected individuals was lower than found in FFV/FeLV co-infected cats in buccal swabs (p = 0.003). We found 78% of cats had detectable buccal FFV DNA in FFV mono-infected and FFV co-infected FeLV-progressive cats, while in FeLV-regressive cats (those without signs of disease) 22% of cats had detectable buccal FFV DNA (p = 0.004). Our results suggest that regressive FeLV infection may reduce FFV saliva transmission, the main mode of FV transmission. We did not find evidence of differences in pathogenicity in FFV mono- and -dually infected cats. In summary, we show that FVs may interact with FeLV within the same host. Our study supports the utility of cats naturally co-infected with retroviruses as a model to investigate the impact of FV on immunocompromised mammalian hosts.
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Wei G, Kehl T, Bao Q, Benner A, Lei J, Löchelt M. The chromatin binding domain, including the QPQRYG motif, of feline foamy virus Gag is required for viral DNA integration and nuclear accumulation of Gag and the viral genome. Virology 2018; 524:56-68. [PMID: 30145377 DOI: 10.1016/j.virol.2018.08.007] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2018] [Revised: 08/08/2018] [Accepted: 08/08/2018] [Indexed: 01/15/2023]
Abstract
The retroviral Gag protein, the major component of released particles, plays different roles in particle assembly, maturation or infection of new host cells. Here, we characterize the Gag chromatin binding site including the highly conserved QPQRYG motif of feline foamy virus, a member of the Spumaretrovirinae. Mutagenesis of critical residues in the chromatin binding site/QPQRYG motif almost completely abrogates viral DNA integration and reduces nuclear accumulation of Gag and viral DNA. Genome packaging, reverse transcription, particle release and uptake into new target cells are not affected. The integrity of the QPQRYG motif appears to be important for processes after cytosolic entry, likely influencing incoming virus capsids or disassembly intermediates but not Gag synthesized de novo in progeny virus-producing cells. According to our data, chromatin binding is a shared feature among foamy viruses but further work is needed to understand the mechanisms involved.
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Affiliation(s)
- Guochao Wei
- Division of Molecular Diagnostics of Oncogenic Infections, Research Focus Infection, Inflammation and Cancer, German Cancer Research Center (Deutsches Krebsforschungszentrum, DKFZ), Heidelberg, Germany
| | - Timo Kehl
- Division of Molecular Diagnostics of Oncogenic Infections, Research Focus Infection, Inflammation and Cancer, German Cancer Research Center (Deutsches Krebsforschungszentrum, DKFZ), Heidelberg, Germany
| | - Qiuying Bao
- Division of Molecular Diagnostics of Oncogenic Infections, Research Focus Infection, Inflammation and Cancer, German Cancer Research Center (Deutsches Krebsforschungszentrum, DKFZ), Heidelberg, Germany
| | - Axel Benner
- Division of Biostatistics, German Cancer Research Center (Deutsches Krebsforschungszentrum, DKFZ), Heidelberg, Germany
| | - Janet Lei
- Division of Molecular Diagnostics of Oncogenic Infections, Research Focus Infection, Inflammation and Cancer, German Cancer Research Center (Deutsches Krebsforschungszentrum, DKFZ), Heidelberg, Germany
| | - Martin Löchelt
- Division of Molecular Diagnostics of Oncogenic Infections, Research Focus Infection, Inflammation and Cancer, German Cancer Research Center (Deutsches Krebsforschungszentrum, DKFZ), Heidelberg, Germany.
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Hamann MV, Lindemann D. Foamy Virus Protein-Nucleic Acid Interactions during Particle Morphogenesis. Viruses 2016; 8:v8090243. [PMID: 27589786 PMCID: PMC5035957 DOI: 10.3390/v8090243] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2016] [Revised: 08/19/2016] [Accepted: 08/22/2016] [Indexed: 12/24/2022] Open
Abstract
Compared with orthoretroviruses, our understanding of the molecular and cellular replication mechanism of foamy viruses (FVs), a subfamily of retroviruses, is less advanced. The FV replication cycle differs in several key aspects from orthoretroviruses, which leaves established retroviral models debatable for FVs. Here, we review the general aspect of the FV protein-nucleic acid interactions during virus morphogenesis. We provide a summary of the current knowledge of the FV genome structure and essential sequence motifs required for RNA encapsidation as well as Gag and Pol binding in combination with details about the Gag and Pol biosynthesis. This leads us to address open questions in FV RNA engagement, binding and packaging. Based on recent findings, we propose to shift the point of view from individual glycine-arginine-rich motifs having functions in RNA interactions towards envisioning the FV Gag C-terminus as a general RNA binding protein module. We encourage further investigating a potential new retroviral RNA packaging mechanism, which seems more complex in terms of the components that need to be gathered to form an infectious particle. Additional molecular insights into retroviral protein-nucleic acid interactions help us to develop safer, more specific and more efficient vectors in an era of booming genome engineering and gene therapy approaches.
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Affiliation(s)
- Martin V Hamann
- Institute of Virology, Medical Faculty Carl Gustav Carus, Technische Universität Dresden, 01307 Dresden, Germany.
- CRTD/DFG-Center for Regenerative Therapies Dresden, Technische Universität Dresden, 01307 Dresden, Germany.
| | - Dirk Lindemann
- Institute of Virology, Medical Faculty Carl Gustav Carus, Technische Universität Dresden, 01307 Dresden, Germany.
- CRTD/DFG-Center for Regenerative Therapies Dresden, Technische Universität Dresden, 01307 Dresden, Germany.
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Weber C, Armbruster N, Scheller C, Kreppel F, Kochanek S, Rethwilm A, Steinert AF. Foamy virus-adenovirus hybrid vectors for gene therapy of the arthritides. J Gene Med 2013; 15:155-67. [PMID: 23554302 DOI: 10.1002/jgm.2705] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2012] [Revised: 03/24/2013] [Accepted: 03/25/2013] [Indexed: 12/30/2022] Open
Abstract
BACKGROUND Genetic treatments of chronic arthritic conditions are essentially dependent on safe and efficient vector systems. To combine features of the efficient transduction of adenovirus vectors with the advantage of stable integration into the host cell genome of apathogenic prototype foamy virus vectors, hybrid vectors (FAD) have been established. In the present study, we have generated and investigated the use of safe FAD vectors for direct gene delivery to joints. METHODS We generated recombinant FAD encoding enhanced green fluorescent protein (EGFP) or human interleukin 1 receptor antagonist protein (IL1RA) cDNA, and explored their transgene expression profile, as well as the bioactivity of the IL1RA transgene in vitro. The feasibility of IL1RA gene delivery to articular tissues was investigated in a pilot study employing direct FAD injections to the knee joints of Wistar rats. RESULTS FAD vectors efficiently transduced human or rat fibroblasts with EGFP or IL1RA transgene in vitro. Levels of IL1RA transgene expression were high, stable and functional in vitro. Transduced synovial fibroblasts and high levels of IL1RA protein (10-35 ng/ml) could be detected in vivo in the synovium of Wistar rats 3-5 days after injection of FAD vectors to the knee joints. CONCLUSIONS Our results indicate that FAD vectors are capable of efficient in vivo gene transfer to synovium and merit further investigation as a means of providing efficient and long-term intra-articular transgene expression for treatment of the arthritides.
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Affiliation(s)
- Conrad Weber
- University of Würzburg, Department of Virology and Immunobiology, Würzburg, Germany
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12
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Rethwilm A. Specific RNA-protein interactions in the replication of foamy viruses (FVs). Curr Opin Virol 2013; 3:676-83. [PMID: 24119459 DOI: 10.1016/j.coviro.2013.09.003] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2013] [Revised: 09/10/2013] [Accepted: 09/10/2013] [Indexed: 11/25/2022]
Abstract
The FV pathway of replication is fundamentally different from what we know about the strategy employed by all known other retroviruses. This unique pathway involves some distinctive RNA-protein interactions, which range from nuclear RNA export to activation of reverse transcription late in the viral replication cycle. Some peculiarities of this replication strategy will be summarized here.
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Affiliation(s)
- Axel Rethwilm
- Universität Würzburg, Institut für Virologie und Immunbiologie, Versbacher Str. 7, 97078 Würzburg, Germany.
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13
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Rethwilm A, Bodem J. Evolution of foamy viruses: the most ancient of all retroviruses. Viruses 2013; 5:2349-74. [PMID: 24072062 PMCID: PMC3814592 DOI: 10.3390/v5102349] [Citation(s) in RCA: 45] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2013] [Revised: 08/27/2013] [Accepted: 09/18/2013] [Indexed: 12/24/2022] Open
Abstract
Recent evidence indicates that foamy viruses (FVs) are the oldest retroviruses (RVs) that we know and coevolved with their hosts for several hundred million years. This coevolution may have contributed to the non-pathogenicity of FVs, an important factor in development of foamy viral vectors in gene therapy. However, various questions on the molecular evolution of FVs remain still unanswered. The analysis of the spectrum of animal species infected by exogenous FVs or harboring endogenous FV elements in their genome is pivotal. Furthermore, animal studies might reveal important issues, such as the identification of the FV in vivo target cells, which than require a detailed characterization, to resolve the molecular basis of the accuracy with which FVs copy their genome. The issues of the extent of FV viremia and of the nature of the virion genome (RNA vs. DNA) also need to be experimentally addressed.
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Affiliation(s)
- Axel Rethwilm
- Universität Würzburg, Institut für Virologie und Immunbiologie, Versbacher Str.7, Würzburg 97078, Germany.
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Kehl T, Tan J, Materniak M. Non-simian foamy viruses: molecular virology, tropism and prevalence and zoonotic/interspecies transmission. Viruses 2013; 5:2169-209. [PMID: 24064793 PMCID: PMC3798896 DOI: 10.3390/v5092169] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2013] [Revised: 09/04/2013] [Accepted: 09/05/2013] [Indexed: 12/27/2022] Open
Abstract
Within the field of retrovirus, our knowledge of foamy viruses (FV) is still limited. Their unique replication strategy and mechanism of viral persistency needs further research to gain understanding of the virus-host interactions, especially in the light of the recent findings suggesting their ancient origin and long co-evolution with their nonhuman hosts. Unquestionably, the most studied member is the primate/prototype foamy virus (PFV) which was originally isolated from a human (designated as human foamy virus, HFV), but later identified as chimpanzee origin; phylogenetic analysis clearly places it among other Old World primates. Additionally, the study of non-simian animal FVs can contribute to a deeper understanding of FV-host interactions and development of other animal models. The review aims at highlighting areas of special interest regarding the structure, biology, virus-host interactions and interspecies transmission potential of primate as well as non-primate foamy viruses for gaining new insights into FV biology.
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Affiliation(s)
- Timo Kehl
- German Cancer Research Center, INF242, Heidelberg 69120, Germany
- Author to whom correspondence should be addressed; E-Mail: ; Tel.: +49-6221-42-4935; Fax: +49-6221-42-4932
| | - Juan Tan
- College of Life Sciences, Nankai University, 94 Weijin Road, Tianjin 300071, China; E-Mail:
| | - Magdalena Materniak
- Department of Biochemistry, National Veterinary Research Institute, Partyzantow Ave. 57, Pulawy 24-100, Poland; E-Mail:
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Liu W, Lei J, Liu Y, Slavkovic Lukic D, Räthe AM, Bao Q, Kehl T, Bleiholder A, Hechler T, Löchelt M. Feline foamy virus-based vectors: advantages of an authentic animal model. Viruses 2013; 5:1702-18. [PMID: 23857307 PMCID: PMC3738957 DOI: 10.3390/v5071702] [Citation(s) in RCA: 12] [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: 03/01/2013] [Revised: 06/13/2013] [Accepted: 06/25/2013] [Indexed: 02/07/2023] Open
Abstract
New-generation retroviral vectors have potential applications in vaccination and gene therapy. Foamy viruses are particularly interesting as vectors, because they are not associated to any disease. Vector research is mainly based on primate foamy viruses (PFV), but cats are an alternative animal model, due to their smaller size and the existence of a cognate feline foamy virus (FFV). The potential of replication-competent (RC) FFV vectors for vaccination and replication-deficient (RD) FFV-based vectors for gene delivery purposes has been studied over the past years. In this review, the key achievements and functional evaluation of the existing vectors from in vitro cell culture systems to out-bred cats will be described. The data presented here demonstrate the broad application spectrum of FFV-based vectors, especially in pathogen-specific prophylactic and therapeutic vaccination using RD vectors in cats and in classical gene delivery. In the cat-based system, FFV-based vectors provide an advantageous platform to evaluate and optimize the applicability, efficacy and safety of foamy virus (FV) vectors, especially the understudied aspect of FV cell and organ tropism.
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Affiliation(s)
| | | | | | | | | | | | | | | | | | - Martin Löchelt
- Department of Genome Modifications, Research Program Infection and Cancer, German Cancer Research Center, Im Neuenheimer Feld 242, 69120 Heidelberg, Germany; E-Mails: (W.L.); (J.L.); (Y.L.); (D.S.L.); (A.-M.R.); (Q.B.); (T.K.); (A.B.); (T.H.)
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The foamy virus Gag proteins: what makes them different? Viruses 2013; 5:1023-41. [PMID: 23531622 PMCID: PMC3705263 DOI: 10.3390/v5041023] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2013] [Revised: 03/15/2013] [Accepted: 03/20/2013] [Indexed: 12/15/2022] Open
Abstract
Gag proteins play an important role in many stages of the retroviral replication cycle. They orchestrate viral assembly, interact with numerous host cell proteins, engage in regulation of viral gene expression, and provide the main driving force for virus intracellular trafficking and budding. Foamy Viruses (FV), also known as spumaviruses, display a number of unique features among retroviruses. Many of these features can be attributed to their Gag proteins. FV Gag proteins lack characteristic orthoretroviral domains like membrane-binding domains (M domains), the major homology region (MHR), and the hallmark Cys-His motifs. In contrast, they contain several distinct domains such as the essential Gag-Env interaction domain and the glycine and arginine rich boxes (GR boxes). Furthermore, FV Gag only undergoes limited maturation and follows an unusual pathway for nuclear translocation. This review summarizes the known FV Gag domains and motifs and their functions. In particular, it provides an overview of the unique structural and functional properties that distinguish FV Gag proteins from orthoretroviral Gag proteins.
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Complete Genome Sequences of Two Novel Puma concolor Foamy Viruses from California. GENOME ANNOUNCEMENTS 2013; 1:e0020112. [PMID: 23516229 PMCID: PMC3622991 DOI: 10.1128/genomea.00201-12] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
We report two complete foamy retrovirus (FV) genomes isolated from Puma concolor, a large cat native to the Americas. Due to high overall genetic relatedness to known feline foamy viruses (FFVs), we propose the name Puma concolor FFV (FFVPc). The data confirm that felines are infected with distinct but closely related FVs.
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Abstract
The cellular receptor of foamy viruses (FVs) is unknown. The broad spectrum of permissive cells suggests that the cellular receptor is a molecular structure with almost ubiquitous prevalence. Here, we investigated the ability of heparan sulfate (HS), a glycosaminoglycan (GAG) present on the extracellular matrix of many cells, to bind FV particles and to permit prototype FV (PFV) and feline FV (FFV) entry. Permissivity of different cell lines for FV entry correlated with the amount of heparan sulfate present on the cell surface. The resulting 50% cell culture infectious doses (CCID(50)s) were distributed over a range of 4 logs, which means that the most susceptible cell line tested (HT1080) was more than 10,000 times more susceptible for PFV infection than the least susceptible cell line (CRL-2242). HS surface expression varied over a range of 2 logs. HS expression and FV susceptibility were positively correlated (P < 0.001). Enzymatic digestion of heparan sulfate on HT1080 cells diminished permissivity for PFV entry by a factor of at least 500. Using fast protein liquid chromatography (FPLC), we demonstrated binding of FV vector particles to a gel filtration column packed with heparin, a molecule structurally related to heparan sulfate, allowing for the purification of infectious particles. Both PFV and FFV infection were inhibited by soluble heparin. Our results show that FVs bind to HS and that this interaction is a pivotal step for viral entry, suggesting that HS is a cellular attachment factor for FVs.
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Lindemann D, Rethwilm A. Foamy virus biology and its application for vector development. Viruses 2011; 3:561-85. [PMID: 21994746 PMCID: PMC3185757 DOI: 10.3390/v3050561] [Citation(s) in RCA: 71] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2011] [Revised: 04/21/2011] [Accepted: 04/23/2011] [Indexed: 01/12/2023] Open
Abstract
Spuma- or foamy viruses (FV), endemic in most non-human primates, cats, cattle and horses, comprise a special type of retrovirus that has developed a replication strategy combining features of both retroviruses and hepadnaviruses. Unique features of FVs include an apparent apathogenicity in natural hosts as well as zoonotically infected humans, a reverse transcription of the packaged viral RNA genome late during viral replication resulting in an infectious DNA genome in released FV particles and a special particle release strategy depending capsid and glycoprotein coexpression and specific interaction between both components. In addition, particular features with respect to the integration profile into the host genomic DNA discriminate FV from orthoretroviruses. It appears that some inherent properties of FV vectors set them favorably apart from orthoretroviral vectors and ask for additional basic research on the viruses as well as on the application in Gene Therapy. This review will summarize the current knowledge of FV biology and the development as a gene transfer system.
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Affiliation(s)
- Dirk Lindemann
- Institut für Virologie, Medizinische Fakultät “Carl Gustav Carus”, Technische Universität Dresden, Fetscherstr. 74, 01307 Dresden, Germany
- DFG-Center for Regenerative Therapies Dresden (CRTD)—Cluster of Excellence, Biotechnology Center, Technische Universität Dresden, Fetscherstr. 74, 01307 Dresden, Germany
| | - Axel Rethwilm
- Institut für Virologie und Immunbiologie, Universität Würzburg, 97078 Würzburg, Germany; E-Mail:
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Abstract
Foamy virus (FV) capsid proteins have few lysines. Basic residues are almost exclusively represented by arginines indicating positive selective pressure. To analyze the possible functions of this peculiarity, we mutated an infectious molecular clone of the prototypic FV (PFV) to harbor lysines in the Gag protein at arginine-specifying positions and analyzed various aspects of the FV replication cycle. The majority of mutants replicated equally as well in permanent cell cultures as the original wild-type (wt) virus and were genetically stable in gag upon 10 cell-free passages. With respect to the features of late reverse transcription, nucleic acid content, and infectiousness of the virion DNA genome, the majority of mutants behaved like the wt. Several mutants of PFV were ubiquitinated in Gag but unable to generate virus-like particles (VLPs) or to undergo pseudotyping by a heterologous envelope. Using primary cells, however, a replicative disadvantage of the majority of mutants was disclosed. This disadvantage was enhanced upon interferon (IFN) treatment. We found no evidence that the lysine-bearing gag mutants showed more restriction than the wt virus by tetherin (CD317) or Trim5α. A single lysine in PFV Gag was found to be nonessential for transient replication in permanent cell culture if replaced by an arginine residue. Upon replication in primary cells, even without IFN treatment, this mutant was severely impaired, indicating the importance of specifying at least this lysine residue in PFV Gag. The paucity of lysines in FV Gag proteins may be a consequence of preventing proteasomal Gag degradation.
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Novel functions of prototype foamy virus Gag glycine- arginine-rich boxes in reverse transcription and particle morphogenesis. J Virol 2010; 85:1452-63. [PMID: 21106749 DOI: 10.1128/jvi.01731-10] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Prototype foamy virus (PFV) Gag lacks the characteristic orthoretroviral Cys-His motifs that are essential for various steps of the orthoretroviral replication cycle, such as RNA packaging, reverse transcription, infectivity, integration, and viral assembly. Instead, it contains three glycine-arginine-rich boxes (GR boxes) in its C terminus that putatively represent a functional equivalent. We used a four-plasmid replication-deficient PFV vector system, with uncoupled RNA genome packaging and structural protein translation, to analyze the effects of deletion and various substitution mutations within each GR box on particle release, particle-associated protein composition, RNA packaging, DNA content, infectivity, particle morphology, and intracellular localization. The degree of viral particle release by all mutants was similar to that of the wild type. Only minimal effects on Pol encapsidation, exogenous reverse transcriptase (RT) activity, and genomic viral RNA packaging were observed. In contrast, particle-associated DNA content and infectivity were drastically reduced for all deletion mutants and were undetectable for all alanine substitution mutants. Furthermore, GR box I mutants had significant changes in particle morphology, and GR box II mutants lacked the typical nuclear localization pattern of PFV Gag. Finally, it could be shown that GR boxes I and III, but not GR box II, can functionally complement each other. It therefore appears that, similar to the orthoretroviral Cys-His motifs, the PFV Gag GR boxes are important for RNA encapsidation, genome reverse transcription, and virion infectivity as well as for particle morphogenesis.
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Abstract
Foamy viruses (FVs), or spumaviruses, are integrating retroviruses that have been developed as vectors. Here we generated nonintegrating foamy virus (NIFV) vectors by introducing point mutations into the highly conserved DD35E catalytic core motif of the foamy virus integrase sequence. NIFV vectors produced high-titer stocks, transduced dividing cells, and did not integrate. Cells infected with NIFV vectors contained episomal vector genomes that consisted of linear, 1-long-terminal-repeat (1-LTR), and 2-LTR circular DNAs. These episomes expressed transgenes, were stable, and became progressively diluted in the dividing cell population. 1-LTR circles but not 2-LTR circles were found in all vector stocks prior to infection. Residual integration of NIFV vectors occurred at a frequency 4 logs lower than that of integrase-proficient FV vectors. Cre recombinase expressed from a NIFV vector mediated excision of both an integrated, floxed FV vector and a gene-targeted neo expression cassette, demonstrating the utility of these episomal vectors. The broad host range and large packaging capacity of NIFV vectors should make them useful for a variety of applications requiring transient gene expression.
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Zamborlini A, Renault N, Saïb A, Delelis O. Early reverse transcription is essential for productive foamy virus infection. PLoS One 2010; 5:e11023. [PMID: 20552014 PMCID: PMC2884000 DOI: 10.1371/journal.pone.0011023] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2010] [Accepted: 05/18/2010] [Indexed: 11/19/2022] Open
Abstract
BACKGROUND Although viral RNA constitutes the majority of nucleic acids packaged in virions, a late occurring step of reverse transcription leads to the presence of infectious viral cDNA in foamy virus particles. This peculiarity distinguishes them from the rest of the retroviral family. PRINCIPAL FINDINGS To evaluate the respective contribution of these viral nucleic acids in the replication of foamy viruses, their fate was studied by real-time PCR and RT-PCR early after infection, in the presence or in the absence of AZT. We found that an early reverse transcription step, which occurs during the first hours post-entry, is absolutely required for productive infection. Remarkably, sensitivity to AZT can be counteracted by increasing the multiplicity of infection (moi). We also show that 2-LTR circular viral DNA, which appears as soon as four hours post-infection, is transcriptionally competent. CONCLUSION Taken together, our data demonstrate that an early reverse transcription process, which takes place soon after viral entry, is indispensable for infectivity of FVs at low moi, when the amount of DNA-containing particles is not sufficient to lead to a productive infection. This study demonstrates a key role of the packaged viral RNA in the foamy virus infection, suggesting that the replication of this virus can be achieved by involving either viral DNA or RNA genome, depending on the condition of infection.
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Affiliation(s)
- Alessia Zamborlini
- CNRS UMR7212, Inserm U944, Université Paris Diderot, Institut Universitaire d'Hématologie, Paris, France
| | - Noémie Renault
- CNRS UMR7212, Inserm U944, Université Paris Diderot, Institut Universitaire d'Hématologie, Paris, France
| | - Ali Saïb
- CNRS UMR7212, Inserm U944, Université Paris Diderot, Institut Universitaire d'Hématologie, Paris, France
- Chaire de Biologie, Conservatoire National des Arts et Métiers, Paris, France
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Abstract
One of the most fascinating areas in retrovirology is the study of foamy viruses (FVs), because these viruses appear to do everything that is common to all other retroviruses differently. FVs have found a completely new way to propagate their genome. And they do this extremely successfully because most of wild non-human primates, felines, bovines, equines, and small ruminants are likely to be non-pathogenically infected. The success of FVs can also be viewed from a different angle, since they replicate very conservatively and do not need to shape their genotypic and phenotypic makeup every now and then. The elucidation of the underlying basic mechanisms of the FV replication strategy is the topic of this review.
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Schepetilnikov M, Schott G, Katsarou K, Thiébeauld O, Keller M, Ryabova LA. Molecular dissection of the prototype foamy virus (PFV) RNA 5'-UTR identifies essential elements of a ribosomal shunt. Nucleic Acids Res 2009; 37:5838-47. [PMID: 19638424 PMCID: PMC2761275 DOI: 10.1093/nar/gkp609] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
The prototype foamy virus (PFV) is a nonpathogenic retrovirus that shows promise as a vector for gene transfer. The PFV (pre)genomic RNA starts with a long complex leader that can be folded into an elongated hairpin, suggesting an alternative strategy to cap-dependent linear scanning for translation initiation of the downstream GAG open reading frame (ORF). We found that the PFV leader carries several short ORFs (sORFs), with the three 5′-proximal sORFs located upstream of a structural element. Scanning-inhibitory hairpin insertion analysis suggested a ribosomal shunt mechanism, whereby ribosomes start scanning at the leader 5′-end and initiate at the downstream ORF via bypass of the central leader regions, which are inhibitory for scanning. We show that the efficiency of shunting depends strongly on the stability of the structural element located downstream of either sORFs A/A′ or sORF B, and on the translation event at the corresponding 5′-proximal sORF. The PFV shunting strategy mirrors that of Cauliflower mosaic virus in plants; however, in mammals shunting can operate in the presence of a less stable structural element, although it is greatly improved by increasing the number of base pairings. At least one shunt configuration was found in primate FV (pre)genomic RNAs.
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Affiliation(s)
- Mikhail Schepetilnikov
- Institut de Biologie Moléculaire des Plantes du CNRS, Université de Strasbourg, 12 rue du Général Zimmer, 67084 Strasbourg Cedex, France
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The C terminus of foamy retrovirus Gag contains determinants for encapsidation of Pol protein into virions. J Virol 2008; 82:10803-10. [PMID: 18715914 DOI: 10.1128/jvi.00812-08] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Foamy viruses (FV) differ from orthoretroviruses in many aspects of their replication cycle. A major difference is in the mode of Pol expression, regulation, and encapsidation into virions. Orthoretroviruses synthesize Pol as a Gag-Pol fusion protein so that Pol is encapsidated into virus particles through Gag assembly domains. However, as FV express Pol independently of Gag from a spliced mRNA, packaging occurs through a distinct mechanism. FV genomic RNA contains cis-acting sequences that are required for Pol packaging, suggesting that Pol binds to RNA for its encapsidation. However, it is not known whether Gag is directly involved in Pol packaging. Previously our laboratory showed that sequences flanking the three glycine-arginine-rich (GR) boxes at the C terminus of FV Gag contain domains important for RNA packaging and Pol expression, cleavage, and packaging. We have now shown that both deletion and substitution mutations in the first GR box (GR1) prevented neither the assembly of particles with wild-type density nor packaging of RNA genomes but led to a defect in Pol packaging. Site-directed mutagenesis of GR1 indicated that the clustered positively charged amino acids in GR1 play important roles in Pol packaging. Our results suggest that GR1 contains a Pol interaction domain and that a Gag-Pol complex is formed and binds to RNA for incorporation into virions.
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Liu W, Worobey M, Li Y, Keele BF, Bibollet-Ruche F, Guo Y, Goepfert PA, Santiago ML, Ndjango JBN, Neel C, Clifford SL, Sanz C, Kamenya S, Wilson ML, Pusey AE, Gross-Camp N, Boesch C, Smith V, Zamma K, Huffman MA, Mitani JC, Watts DP, Peeters M, Shaw GM, Switzer WM, Sharp PM, Hahn BH. Molecular ecology and natural history of simian foamy virus infection in wild-living chimpanzees. PLoS Pathog 2008; 4:e1000097. [PMID: 18604273 PMCID: PMC2435277 DOI: 10.1371/journal.ppat.1000097] [Citation(s) in RCA: 115] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2008] [Accepted: 06/05/2008] [Indexed: 12/31/2022] Open
Abstract
Identifying microbial pathogens with zoonotic potential in wild-living primates can be important to human health, as evidenced by human immunodeficiency viruses types 1 and 2 (HIV-1 and HIV-2) and Ebola virus. Simian foamy viruses (SFVs) are ancient retroviruses that infect Old and New World monkeys and apes. Although not known to cause disease, these viruses are of public health interest because they have the potential to infect humans and thus provide a more general indication of zoonotic exposure risks. Surprisingly, no information exists concerning the prevalence, geographic distribution, and genetic diversity of SFVs in wild-living monkeys and apes. Here, we report the first comprehensive survey of SFVcpz infection in free-ranging chimpanzees (Pan troglodytes) using newly developed, fecal-based assays. Chimpanzee fecal samples (n = 724) were collected at 25 field sites throughout equatorial Africa and tested for SFVcpz-specific antibodies (n = 706) or viral nucleic acids (n = 392). SFVcpz infection was documented at all field sites, with prevalence rates ranging from 44% to 100%. In two habituated communities, adult chimpanzees had significantly higher SFVcpz infection rates than infants and juveniles, indicating predominantly horizontal rather than vertical transmission routes. Some chimpanzees were co-infected with simian immunodeficiency virus (SIVcpz); however, there was no evidence that SFVcpz and SIVcpz were epidemiologically linked. SFVcpz nucleic acids were recovered from 177 fecal samples, all of which contained SFVcpz RNA and not DNA. Phylogenetic analysis of partial gag (616 bp), pol-RT (717 bp), and pol-IN (425 bp) sequences identified a diverse group of viruses, which could be subdivided into four distinct SFVcpz lineages according to their chimpanzee subspecies of origin. Within these lineages, there was evidence of frequent superinfection and viral recombination. One chimpanzee was infected by a foamy virus from a Cercopithecus monkey species, indicating cross-species transmission of SFVs in the wild. These data indicate that SFVcpz (i) is widely distributed among all chimpanzee subspecies; (ii) is shed in fecal samples as viral RNA; (iii) is transmitted predominantly by horizontal routes; (iv) is prone to superinfection and recombination; (v) has co-evolved with its natural host; and (vi) represents a sensitive marker of population structure that may be useful for chimpanzee taxonomy and conservation strategies.
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Affiliation(s)
- Weimin Liu
- Departments of Medicine and Microbiology, University of Alabama at Birmingham, Birmingham, Alabama, United States of America
| | - Michael Worobey
- University of Arizona, Tucson, Arizona, United States of America
| | - Yingying Li
- Departments of Medicine and Microbiology, University of Alabama at Birmingham, Birmingham, Alabama, United States of America
| | - Brandon F. Keele
- Departments of Medicine and Microbiology, University of Alabama at Birmingham, Birmingham, Alabama, United States of America
| | - Frederic Bibollet-Ruche
- Departments of Medicine and Microbiology, University of Alabama at Birmingham, Birmingham, Alabama, United States of America
| | - Yuanyuan Guo
- Departments of Medicine and Microbiology, University of Alabama at Birmingham, Birmingham, Alabama, United States of America
| | - Paul A. Goepfert
- Departments of Medicine and Microbiology, University of Alabama at Birmingham, Birmingham, Alabama, United States of America
| | - Mario L. Santiago
- Gladstone Institute for Virology and Immunology, University of California at San Francisco, San Francisco, California, United States of America
| | | | - Cecile Neel
- Institut de Recherche pour le Développement (IRD) and University of Montpellier 1, Montpellier, France
- Projet Prevention du Sida ou Cameroun (PRESICA), Yaoundé, Cameroun
| | - Stephen L. Clifford
- Centre International de Recherches Medicales de Franceville (CIRMF), Franceville, Gabon
| | - Crickette Sanz
- Max-Planck Institute for Evolutionary Anthropology, Leipzig, Germany
| | - Shadrack Kamenya
- Gombe Stream Research Centre, The Jane Goodall Institute, Tanzania
| | - Michael L. Wilson
- Department of Anthropology, University of Minnesota, Minneapolis, Minnesota, United States of America
| | - Anne E. Pusey
- Jane Goodall Institute's Center for Primate Studies, Department of Ecology, Evolution and Behavior, University of Minnesota, St. Paul, Minnesota, United States of America
| | - Nicole Gross-Camp
- Antioch New England Graduate School, Keene, New Hampshire, United States of America
| | - Christophe Boesch
- Max-Planck Institute for Evolutionary Anthropology, Leipzig, Germany
| | | | - Koichiro Zamma
- Great Ape Research Institute, Hayashibara Biochemical Laboratories, Okayama, Japan
| | - Michael A. Huffman
- Section of Ecology, Primate Research Institute, Kyoto University, Aichi, Japan
| | - John C. Mitani
- Department of Anthropology, University of Michigan, Ann Arbor, Michigan, United States of America
| | - David P. Watts
- Department of Anthropology, Yale University, New Haven, Connecticut, United States of America
| | - Martine Peeters
- Institut de Recherche pour le Développement (IRD) and University of Montpellier 1, Montpellier, France
| | - George M. Shaw
- Departments of Medicine and Microbiology, University of Alabama at Birmingham, Birmingham, Alabama, United States of America
| | - William M. Switzer
- Laboratory Branch, National Center for HIV/AIDS, STD, and TB Prevention, Centers for Disease Control and Prevention, Atlanta, Georgia, United States of America
| | - Paul M. Sharp
- Institute of Evolutionary Biology, University of Edinburgh, Edinburgh, United Kingdom
| | - Beatrice H. Hahn
- Departments of Medicine and Microbiology, University of Alabama at Birmingham, Birmingham, Alabama, United States of America
- * E-mail:
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Hartl MJ, Wöhrl BM, Rösch P, Schweimer K. The solution structure of the simian foamy virus protease reveals a monomeric protein. J Mol Biol 2008; 381:141-9. [PMID: 18597783 DOI: 10.1016/j.jmb.2008.05.064] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2008] [Revised: 05/23/2008] [Accepted: 05/27/2008] [Indexed: 10/22/2022]
Abstract
In contrast to orthoretroviruses, foamy viruses (FVs) express their Pol polyprotein from a separate pol-specific transcript. Only the integrase domain is cleaved off, leading to a protease-reverse transcriptase (PR-RT) protein. We purified the separate PR domain (PRshort) of simian FV from macaques by expressing the recombinant gene in Escherichia coli. Sedimentation analyses and size exclusion chromatography indicate that PRshort is a stable monomer in solution. This allowed us to determine the structure of the PRshort monomer using 1426 experimental restraints derived from NMR spectroscopy. The superposition of 20 conformers resulted in a backbone atom rmsd of 0.55 A for residues Gln8-Leu93. Although the overall folds are similar, the macaque simian FV PRshort reveals significant differences in the dimerization interface relative to other retroviral PRs, such as HIV-1 (human immunodeficiency virus type 1) PR, which appear to be rather stable dimers. Especially the flap region and the N- and C-termini of PRshort are highly flexible. Neglecting these regions, the backbone atom rmsd drops to 0.32 A, highlighting the good definition of the central part of the protein. To exclude that the monomeric state of PRshort is due to cleaving off the RT, we purified the complete PR-RT and performed size exclusion chromatography. Our data show that PR-RT is also monomeric. We thus conclude adoption of a monomeric state of PR-RT to be a regulatory mechanism to inhibit PR activity before virus assembly in order to reduce packaging problems. Dimerization might therefore be triggered by additional viral or cellular factors.
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Affiliation(s)
- Maximilian J Hartl
- Lehrstuhl für Struktur und Chemie der Biopolymere, Universität Bayreuth, 95440 Bayreuth, Germany
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30
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Abstract
Foamy viruses (FVs) are unconventional retroviruses with a replication strategy that is significantly different from orthoretroviruses and bears some homology to that of hepadnaviruses. Although some cellular proteins, such as APOBEC3, have been reported to block FVs, no restriction by Trim5alpha has been described to date. The sensitivity of three FV isolates of human-chimpanzee or prototypic (PFV), macaque (SFVmac), and feline (FFV) origin to a variety of primate Trim5alphas was therefore tested. PFV and SFVmac were restricted by Trim5alphas from most New World monkeys, but not from other primates, whereas FFV-based vectors were restricted by Trim5alphas from the great apes gorilla and orangutan. Trim5alphas from Old World monkeys did not restrict any FV isolate tested. Capuchin Trim5alpha was unique, as it restricted SFVmac and FFV but not PFV. Trim5alpha specificity for FVs was determined by the B30.2 domain, interestingly involving, in some instances, the same residues of the variable regions previously implicated as major determinants for human immunodeficiency virus type 1 restriction. FVs with chimeric Gags were made to map the viral determinants of sensitivity to restriction. The N-terminal half of the Gag molecule was found to contain the regions that control susceptibility. This region most likely corresponds to the capsid of conventional retroviruses. Due to their unique replication strategy, FVs should provide a valuable new system to examine the mechanism of retroviral restriction by Trim5alpha.
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Peters K, Barg N, Gärtner K, Rethwilm A. Complex effects of foamy virus central purine-rich regions on viral replication. Virology 2008; 373:51-60. [PMID: 18078974 DOI: 10.1016/j.virol.2007.10.037] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2007] [Revised: 08/29/2007] [Accepted: 10/30/2007] [Indexed: 10/22/2022]
Abstract
Similar to the lentiviruses family of retroviruses, foamy viruses (FVs) contain purine-rich sequences located in the center of the genome. Their function on viral replication or vector transfer remains elusive, although dual initiation of plus-strand reverse transcription has been suggested. To elucidate the physical nature of the central region of the prototype FV (PFV) genome, we performed 3' and 5' RACE experiments. Our results revealed that the PFV genome contains a centrally located gap in the DNA plus-strand with no definite termination and start point and of variable length. We did not find evidence for a DNA flap region. The PFV isolate harbors four centrally located purine-rich elements (A-D). Only the D element is identical in sequence to the 3' poly purine tract (PPT). We mutated these elements while conserving or altering the overlapping pol reading frame and analyzed the mutants for transient replication in an infectious or for vector transfer in a replication-deficient background. In addition, we determined the protein composition of the respective viral particles. The A and B elements appeared to play a role in Pol protein encapsidation, the C element is likely involved in regulating gene expression, while mutation of the D element resulted in an insignificant reduction in transiently replicating virus and an approximately 50% reduction in vector titer. The reason for this deficit remains to be elucidated.
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Affiliation(s)
- Katrin Peters
- Institut für Virologie und Immunbiologie, Universität Würzburg, Versbacher Str. 7, 97078 Würzburg, Germany
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32
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Kretzschmar B, Nowrouzi A, Hartl MJ, Gärtner K, Wiktorowicz T, Herchenröder O, Kanzler S, Rudolph W, Mergia A, Wöhrl B, Rethwilm A. AZT-resistant foamy virus. Virology 2007; 370:151-7. [PMID: 17904181 PMCID: PMC2276251 DOI: 10.1016/j.virol.2007.08.025] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2007] [Revised: 07/25/2007] [Accepted: 08/21/2007] [Indexed: 11/24/2022]
Abstract
Azidothymidine (AZT) is a reverse transcriptase (RT) inhibitor that efficiently blocks the replication of spumaretroviruses or foamy viruses (FVs). To more precisely elucidate the mechanism of action of the FV RT enzyme, we generated an AZT-resistant FV in cell culture. Biologically resistant virus was obtained for simian foamy virus from macaque (SFVmac), which was insensitive to AZT concentrations of 1 mM, but not for FVs derived from chimpanzees. Nucleotide sequencing revealed four non-silent mutations in the pol gene. Introduction of these mutations into an infectious molecular clone identified all changes to be required for the fully AZT-resistant phenotype of SFVmac. The alteration of individual sites showed that AZT resistance in SFVmac was likely acquired by consecutive acquisition of pol mutations in a defined order, because some alterations on their own did not result in an efficiently replicating virus, neither in the presence nor in the absence of AZT. The introduction of the mutations into the RT of the closely related prototypic FV (PFV) did not yield an AZT-resistant virus, instead they significantly impaired the viral fitness.
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Affiliation(s)
- Benedikt Kretzschmar
- Universität Würzburg, Institut für Virologie und Immunbiologie, Versbacher Str. 7, 97078 Würzburg, Germany
| | - Ali Nowrouzi
- Universität Würzburg, Institut für Virologie und Immunbiologie, Versbacher Str. 7, 97078 Würzburg, Germany
| | | | - Kathleen Gärtner
- Universität Würzburg, Institut für Virologie und Immunbiologie, Versbacher Str. 7, 97078 Würzburg, Germany
| | - Tatiana Wiktorowicz
- Universität Würzburg, Institut für Virologie und Immunbiologie, Versbacher Str. 7, 97078 Würzburg, Germany
| | - Ottmar Herchenröder
- Technische Universität Dresden, Medizinische Fakultät “Carl Gustav Carus,” Institut für Virologie, Dresden, Germany
| | - Sylvia Kanzler
- Technische Universität Dresden, Medizinische Fakultät “Carl Gustav Carus,” Institut für Virologie, Dresden, Germany
| | - Wolfram Rudolph
- Technische Universität Dresden, Medizinische Fakultät “Carl Gustav Carus,” Institut für Virologie, Dresden, Germany
| | - Ayalew Mergia
- Department of Infectious Disease and Pathology, College of Veterinary Medicine, University of Florida, Gainesville, FL, USA
| | - Birgitta Wöhrl
- Universität Bayreuth, Lehrstuhl Biopolymere, Bayreuth, Germany
| | - Axel Rethwilm
- Universität Würzburg, Institut für Virologie und Immunbiologie, Versbacher Str. 7, 97078 Würzburg, Germany
- Corresponding author. Fax: +49 931 201 49553. E-mail address: (A. Rethwilm)
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Thümer L, Rethwilm A, Holmes EC, Bodem J. The complete nucleotide sequence of a New World simian foamy virus. Virology 2007; 369:191-7. [PMID: 17765280 DOI: 10.1016/j.virol.2007.07.018] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2007] [Revised: 06/29/2007] [Accepted: 07/11/2007] [Indexed: 11/25/2022]
Abstract
We determined the complete nucleotide sequence of the New World simian foamy virus (FV) from spider monkey (SFVspm). Starting from a conserved region in the integrase (IN) domain of the pol gene we cloned fragments of the genome up to the 5' end of the long terminal repeat (LTR) into plasmid vectors and elucidated their nucleotide sequence. The 3' end of the genome was determined by direct nucleotide sequencing of PCR products. Each nucleotide of the genome was determined at least two times from both strands. All protein motifs described to be conserved among primate FVs were found in SFVspm. At both the nucleotide and protein levels SFVspm is the most divergent primate FV described to date, reflecting the long-term phylogenetic separation between Old World and New World primate host species (Catarrhini and Platyrrhini, respectively). The molecular probes developed for SFVspm will allow the investigation of trans-species transmissions of this New World foamy virus to humans by serological assays.
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Affiliation(s)
- Leonore Thümer
- Universität Würzburg, Institut für Virologie und Immunbiologie, Versbacher Str. 7, 97078 Würzburg, Germany
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34
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Abstract
Foamy virus Pol precursor protein processing by the viral protease occurs at only one site, releasing a protease-reverse transcriptase and an integrase protein. To examine whether the cleavage of the Pol precursor protein is necessary for enzymatic activities and efficient viral replication, several mutations were generated around the cleavage site. All cleavage site mutants synthesize wild-type levels of Pol precursor protein. Mutants containing more than two amino acid substitutions around the cleavage site exhibit no detectable Pol processing. The Pol cleavage site is not required for the production of infectious particles in a single round of infection, but is important for subsequent rounds of viral infection. Mutations around the cleavage site affected the enzymatic activities of the protease and reverse transcriptase and prevented replication after two rounds of infection. Interestingly, Pol encapsidation is significantly reduced in some of the mutants.
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Affiliation(s)
- Jacqueline Roy
- Division of Basic Sciences, Fred Hutchinson Cancer Research Center, 1100 Fairview Ave. N., Seattle, WA 98109-1024, USA
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35
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Mannigel I, Stange A, Zentgraf H, Lindemann D. Correct capsid assembly mediated by a conserved YXXLGL motif in prototype foamy virus Gag is essential for infectivity and reverse transcription of the viral genome. J Virol 2007; 81:3317-26. [PMID: 17229703 PMCID: PMC1866044 DOI: 10.1128/jvi.01866-06] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Unlike other retrovirus Gag proteins, the prototype foamy virus (PFV) p71(g)(ag) protein is not processed into mature matrix (MA), capsid (CA), and nucleocapsid (NC) subunits. Little information about sequence motifs involved in FV capsid assembly and release is available. The recent analysis of candidate L-domain motifs in PFV Gag identified an evolutionarily conserved YXXL sequence motif with a potential function in capsid assembly. Here we provide support for the hypothesis that this motif does not function like a conventional L domain, by demonstrating that, unlike the PFV Gag PSAP L-domain motif, it cannot be functionally replaced by heterologous L-domain sequences. Furthermore, mutation of individual amino acids Y(464), I(466), L(467), and L(469), but not E(465), to alanine led to reduced particle release and production of noninfectious, aberrant capsid structures, although relative structural protein incorporation and processing were not affected. In contrast, mutation of G(468) to alanine resulted in an intermediate, temperature-sensitive phenotype characterized by reduced particle release and reduced infectivity. Despite similar relative RNA genome incorporation for all mutants, analysis and quantification of particle-associated viral nucleic acids demonstrated defects in genomic reverse transcription for all the noninfectious mutants, a process that, unlike that of orthoretroviruses, in the case of FVs takes place in the virus-producing cell. In correlation with the reduced infectivity, the G(468)A mutant displayed an intermediate level of genomic reverse transcription. Taken together, these results demonstrate that the conserved YXXLGL motif in PFV Gag is involved in correct capsid assembly, which in turn is essential for reverse transcription of the FV genome.
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Affiliation(s)
- Ingrid Mannigel
- Institut für Virologie, Medizinische Fakultät Carl Gustav Carus, Technische Universität Dresden, Fetscherstrasse 74, 01307 Dresden, Germany
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36
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Bastone P, Romen F, Liu W, Wirtz R, Koch U, Josephson N, Langbein S, Löchelt M. Construction and characterization of efficient, stable and safe replication-deficient foamy virus vectors. Gene Ther 2007; 14:613-20. [PMID: 17203107 DOI: 10.1038/sj.gt.3302890] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
As serious side effects affected recent virus-mediated gene transfer studies, novel vectors with improved safety profiles are urgently needed. In the present study, replication-deficient retroviral vectors based on feline foamy virus (FFV) were constructed and analyzed. The novel FFV vectors are devoid of almost the complete env gene plus the internal promoter - accessory bel gene cassette including the gene for the viral transcriptional transactivator Bel1/Tas. In these Bel1/Tas-independent vectors, expression of the lacZ (beta-galactosidase) marker gene is directed by the heterologous, constitutively active human ubiquitin C promoter (ubi). Env-transcomplemented vectors have un-concentrated titers of more than 10(5) transducing units/ml. The vectors allow efficient transduction of a broad array of diverse target cells, which can be increased by repeated vector exposure. However, the number of lacZ marker gene expressing cells decreased slightly upon serial passages of the transduced cells. Vectors carrying a self-inactivating (SIN) deletion of the TATA box and most parts of the viral promoter were not rescued by wt FFV whereas those with the intact or a partially deleted promoter were readily reactivated. This finding indicates that the viral promoters are in fact non-functional, pointing to a highly advantageous safety profile of these new FFV-ubi-lacZ-SIN vectors.
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Affiliation(s)
- P Bastone
- Abt. Genomveränderungen und Karzinogenese, Forschungsschwerpunkt Infektion und Krebs, Deutsches Krebsforschungszentrum, Heidelberg, Germany
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37
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Bastone P, Bravo IG, Löchelt M. Feline foamy virus-mediated marker gene transfer: identification of essential genetic elements and influence of truncated and chimeric proteins. Virology 2006; 348:190-9. [PMID: 16443252 DOI: 10.1016/j.virol.2005.12.022] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2005] [Revised: 11/22/2005] [Accepted: 12/16/2005] [Indexed: 11/16/2022]
Abstract
Retroviral vectors derived from foamy or spumaretroviruses are considered promising tools for targeted gene delivery and vaccination purposes. In order to fully exploit this potential, we identified essential cis-acting sequences on the feline foamy virus (FFV) genome by constructing and analyzing a series of FFV-based replication-deficient vector genomes. Cis-acting sequences essentially required for marker gene transfer were found to be localized at two sites on the FFV genome: (i) in the 5'-untranslated region and close to the gag ATG and (ii) in the central part of the pol gene. The presence of two cis-acting sequences and their relative location on the FFV genome are similar but not identical to the functionally corresponding elements described for simian and primate foamy viruses.
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Affiliation(s)
- Patrizia Bastone
- Department Genome Modifications and Carcinogenesis, Focus Infection and Cancer, German Cancer Research Centre, Heidelberg, Germany
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38
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Cartellieri M, Herchenröder O, Rudolph W, Heinkelein M, Lindemann D, Zentgraf H, Rethwilm A. N-terminal Gag domain required for foamy virus particle assembly and export. J Virol 2005; 79:12464-76. [PMID: 16160174 PMCID: PMC1211529 DOI: 10.1128/jvi.79.19.12464-12476.2005] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
Among the Retroviridae, foamy viruses (FVs) exhibit an unusual way of particle assembly and a highly specific incorporation of envelope protein into progeny virions. We have analyzed deletions and point mutants of the prototypic FV gag gene for capsid assembly and egress, envelope protein incorporation, infectivity, and ultrastructure. Deletions introduced at the 3' end of gag revealed the first 297 amino acids (aa) to be sufficient for specific Env incorporation and export of particulate material. Deletions introduced at the 5' end showed the region between aa 6 and 200 to be dispensable for virus capsid assembly but required for the incorporation of Env and particle egress. Point mutations were introduced in the 5' region of gag to target residues conserved among FVs from different species. Alanine substitutions of residues in a region between aa 40 and 60 resulted in severe alterations in particle morphology. Furthermore, at position 50, this region harbors the conserved arginine that is presumably at the center of a signal sequence directing FV Gag proteins to a cytoplasmic assembly site.
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Affiliation(s)
- Marc Cartellieri
- Institut für Virologie, Medizinische Fakultät, Technische Universität Dresden, Germany
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39
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Cartellieri M, Rudolph W, Herchenröder O, Lindemann D, Rethwilm A. Determination of the relative amounts of Gag and Pol proteins in foamy virus particles. Retrovirology 2005; 2:44. [PMID: 16004609 PMCID: PMC1185564 DOI: 10.1186/1742-4690-2-44] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2005] [Accepted: 07/08/2005] [Indexed: 11/10/2022] Open
Abstract
We determined the relative ratios of Gag and Pol molecules in highly purified virions of spumaretroviruses or foamy viruses (FVs) using monoclonal antibodies and bacterially expressed reference proteins. We found that the cleaved p68Gag moiety dominates in infectious FVs. Furthermore, approximate mean ratios in FV are 16:1 (pr71Gag plus p68Gag:p85RT),12:1 (p68Gag:p85RT), and 10:1 (pr71Gag plus p68Gag:p40IN). Thus, the results indicate that FVs have found a way to incorporate approximately as much Pol protein into their capsids as orthoretroviruses, despite a completely different Pol expression strategy.
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Affiliation(s)
- Marc Cartellieri
- Institut für Virologie, Medizinische Fakultät, Technische, Universität Dresden, Germany
- Institut für Virologie und Immunbiologie, Universität Würzburg, Germany
| | - Wolfram Rudolph
- Institut für Virologie, Medizinische Fakultät, Technische, Universität Dresden, Germany
| | - Ottmar Herchenröder
- Institut für Virologie, Medizinische Fakultät, Technische, Universität Dresden, Germany
| | - Dirk Lindemann
- Institut für Virologie, Medizinische Fakultät, Technische, Universität Dresden, Germany
| | - Axel Rethwilm
- Institut für Virologie und Immunbiologie, Universität Würzburg, Germany
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40
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Peters K, Wiktorowicz T, Heinkelein M, Rethwilm A. RNA and protein requirements for incorporation of the Pol protein into foamy virus particles. J Virol 2005; 79:7005-13. [PMID: 15890940 PMCID: PMC1112116 DOI: 10.1128/jvi.79.11.7005-7013.2005] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Foamy viruses (FVs) generate their Pol protein precursor molecule independently of the Gag protein from a spliced mRNA. This mode of expression raises the question of the mechanism of Pol protein incorporation into the viral particle (capsid). We previously showed that the packaging of (pre)genomic RNA is essential for Pol encapsidation (M. Heinkelein, C. Leurs, M. Rammling, K. Peters, H. Hanenberg, and A. Rethwilm, J. Virol. 76:10069-10073, 2002). Here, we demonstrate that distinct sequences in the RNA, which we termed Pol encapsidation sequences (PES), are required to incorporate Pol protein into the FV capsid. Two PES were found, which are contained in the previously identified cis-acting sequences necessary to transfer an FV vector. One PES is located in the U5 region of the 5' long terminal repeat and one at the 3' end of the pol gene region. Neither element has any significant effect on RNA packaging. However, deletion of either PES resulted in a significant reduction in Pol encapsidation. On the protein level, we show that only the Pol precursor, but not the individual reverse transcriptase (RT) and integrase (IN) subunits, is incorporated into FV particles. However, enzymatic activities of the protease (PR), RT, or IN are not required. Our results strengthen the view that in FVs, (pre)genomic RNA functions as a bridging molecule between Gag and Pol precursor proteins.
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Affiliation(s)
- Katrin Peters
- Institut für Virologie und Immunbiologie, Universität Würzburg, Versbacher Str. 7, 97078 Würzburg, Germany
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41
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Abstract
Foamy viruses (FVs) or spumaviruses were described for the first time in the early 1950s in cell cultures derived from monkey kidneys. Later, FVs were isolated in several mammal species such as cats, cattle and horses. Highly prevalent in non-human primates they are not naturally present in humans, although several cases of simian-to-human transmissions have been described. Interestingly, the replication strategy of FVs differs in many aspects from that of other retroviruses, presenting features that are closely related to pararetroviruses, exemplified by the hepatitis B virus (HBV), but also characteristics that are closely related to yeast retrotransposons. These characteristics led to the creation of a distinct viral subfamily by the International Committee on Virus Taxonomy in 2002; the Spumaretrovirinae.
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Affiliation(s)
- Olivier Delelis
- CNRS UPR9051, Hôpital Saint-Louis, Centre Hayem, 1 Avenue Claude Vellefaux, 75475 Paris Cedex 10, Paris, France
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42
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Juretzek T, Holm T, Gärtner K, Kanzler S, Lindemann D, Herchenröder O, Picard-Maureau M, Rammling M, Heinkelein M, Rethwilm A. Foamy virus integration. J Virol 2004; 78:2472-7. [PMID: 14963145 PMCID: PMC369232 DOI: 10.1128/jvi.78.5.2472-2477.2004] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
It had been suggested that during integration of spumaretroviruses (foamy viruses) the right (U5) end of the cDNA is processed, while the left (U3) remains uncleaved. We confirmed this hypothesis by sequencing two-long terminal repeat (LTR) circle junctions of unintegrated DNA. Based on an infectious foamy virus molecular clone, a set of constructs harboring mutations at the 5' end of the U3 region in the 3' LTR was analyzed for particle export, reverse transcription, and replication. Following transient transfection some mutants were severely impaired in generating infectious virus, while others replicated almost like the wild type. The replication competence of the mutants was unrelated to the cleavability of the newly created U3 end. This became obvious with two mutants both belonging to the high-titer type. One mutant containing a dinucleotide artificially transferred from the right to the left end was trimmed upon integration, while another one with an unrelated dinucleotide in that place was not. The latter construct in particular showed that the canonical TG motif at the beginning of the provirus is not essential for foamy virus integration.
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Affiliation(s)
- Thomas Juretzek
- Institut für Virologie, Medizinische Fakultät Carl Gustav Carus, Technische Universität Dresden, Dresden, Germany
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43
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Heinkelein M, Rammling M, Juretzek T, Lindemann D, Rethwilm A. Retrotransposition and cell-to-cell transfer of foamy viruses. J Virol 2003; 77:11855-8. [PMID: 14557671 PMCID: PMC229254 DOI: 10.1128/jvi.77.21.11855-11858.2003] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
A remarkable feature of the prototype foamy virus (PFV) replication pathway has been reported to consist of the ability to retrotranspose intracellularly with high efficiency (M. Heinkelein, T. Pietschmann, G. Jármy, M. Dressler, H. Imrich, J. Thurow, D. Lindemann, M. Bock, A. Moebes, J. Roy, O. Herchenröder, and A. Rethwilm, EMBO J. 19:3436-3345, 2000). PFV intracellular retrotransposition (IRT) was reported to be enhanced by coexpression of fusion-defective envelope protein. To investigate the possibility of cell-to-cell transfer of PFV genomes, which could mimic IRT, we performed cocultivation experiments with cells transfected with an IRT-competent and marker gene-expressing PFV vector together with cells expressing a different marker and measured cells positive for both markers. The findings corroborated the initial report on IRT of Env-deficient PFV. Furthermore, they indicated that viral cores that have incorporated fusion-deficient Env can be transferred from cell to cell in a cell type-specific manor. One possible explanation consists of a minor alternative cleavage site in Env that can be used to expose the fusion peptide of the Env transmembrane protein, which appears to be required for virus uptake.
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Affiliation(s)
- Martin Heinkelein
- Institut für Virologie, Medizinische Fakultät Carl Gustav Carus, Technische Universität Dresden, Dresden, Germany
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44
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Abstract
The replication strategy of foamy viruses diverges in many aspects from what is commonly accepted as the rules of retroviral replication. Although many questions on the details of the replication pathway are still unanswered, it appears that foamy viruses have adopted a strategy which functionally bridges the retroviral and the hepadnaviral replication pathways. A number of experimental findings in favour of the view that foamy viruses are reverse transcribing DNA viruses which integrate into the host cell genome are discussed.
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Affiliation(s)
- A Rethwilm
- Institut für Virologie, Medizinische Fakultät Carl Gustav Carus, Technische Universität Dresden, Fetscherstr. 74, Dresden, 01307 Germany.
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