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Levraud JP, Palha N, Langevin C, Boudinot P. Through the looking glass: witnessing host-virus interplay in zebrafish. Trends Microbiol 2014; 22:490-7. [PMID: 24865811 DOI: 10.1016/j.tim.2014.04.014] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2014] [Revised: 04/27/2014] [Accepted: 04/30/2014] [Indexed: 12/21/2022]
Abstract
Host-pathogen interactions can be very complex at all scales; understanding organ- or organism-level events require in vivo approaches. Besides traditional host models such as mice, the zebrafish offers an attractive cocktail of optical accessibility and genetic tractability, blended with a vertebrate-type immunity, where innate responses can easily be separated from adaptive ones. Applied to viral infections, this model has revealed unexpected idiosyncrasies among organs, which we believe may apply to the human situation. We also argue that the dynamic analysis of virus spread and immune response in zebrafish make this model particularly well suited to the exploration of the concept of infection tolerance and resistance in relation to viral diseases.
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Affiliation(s)
- Jean-Pierre Levraud
- Institut Pasteur, Macrophages et Développement de l'Immunité, Paris, France; Centre National de la Recherche Scientifique (CNRS), URA 2578, Paris, France.
| | - Nuno Palha
- Institut Pasteur, Macrophages et Développement de l'Immunité, Paris, France; Centre National de la Recherche Scientifique (CNRS), URA 2578, Paris, France
| | - Christelle Langevin
- Institut National de la Recherche Agronomique (INRA), Virologie et Immunologie Moléculaire, Jouy-en-Josas, France
| | - Pierre Boudinot
- Institut National de la Recherche Agronomique (INRA), Virologie et Immunologie Moléculaire, Jouy-en-Josas, France
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202
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Association between latent proviral characteristics and immune activation in antiretrovirus-treated human immunodeficiency virus type 1-infected adults. J Virol 2014; 88:8629-39. [PMID: 24850730 DOI: 10.1128/jvi.01257-14] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023] Open
Abstract
UNLABELLED Generalized immune activation during HIV infection is associated with an increased risk of cardiovascular disease, neurocognitive disease, osteoporosis, metabolic disorders, and physical frailty. The mechanisms driving this immune activation are poorly understood, particularly for individuals effectively treated with antiretroviral medications. We hypothesized that viral characteristics such as sequence diversity may play a role in driving HIV-associated immune activation. We therefore sequenced proviral DNA isolated from peripheral blood mononuclear cells from HIV-infected individuals on fully suppressive antiretroviral therapy. We performed phylogenetic analyses, calculated viral diversity and divergence in the env and pol genes, and determined coreceptor tropism and the frequency of drug resistance mutations. Comprehensive immune profiling included quantification of immune cell subsets, plasma cytokine levels, and intracellular signaling responses in T cells, B cells, and monocytes. These antiretroviral therapy-treated HIV-infected individuals exhibited a wide range of diversity and divergence in both env and pol genes. However, proviral diversity and divergence in env and pol, coreceptor tropism, and the level of drug resistance did not significantly correlate with markers of immune activation. A clinical history of virologic failure was also not significantly associated with levels of immune activation, indicating that a history of virologic failure does not inexorably lead to increased immune activation as long as suppressive antiretroviral medications are provided. Overall, this study demonstrates that latent viral diversity is unlikely to be a major driver of persistent HIV-associated immune activation. IMPORTANCE Chronic immune activation, which is associated with cardiovascular disease, neurologic disease, and early aging, is likely to be a major driver of morbidity and mortality in HIV-infected individuals. Although treatment of HIV with antiretroviral medications decreases the level of immune activation, levels do not return to normal. The factors driving this persistent immune activation, particularly during effective treatment, are poorly understood. In this study, we investigated whether characteristics of the latent, integrated HIV provirus that persists during treatment are associated with immune activation. We found no relationship between latent viral characteristics and immune activation in treated individuals, indicating that qualities of the provirus are unlikely to be a major driver of persistent inflammation. We also found that individuals who had previously failed treatment but were currently effectively treated did not have significantly increased levels of immune activation, providing hope that past treatment failures do not have a lifelong "legacy" impact.
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203
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Woodruff MC, Herndon CN, Heesters BA, Carroll MC. Contextual analysis of immunological response through whole-organ fluorescent imaging. Lymphat Res Biol 2014; 11:121-7. [PMID: 24044754 DOI: 10.1089/lrb.2013.0011] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
BACKGROUND As fluorescent microscopy has developed, significant insights have been gained into the establishment of immune response within secondary lymphoid organs, particularly in draining lymph nodes. While established techniques such as confocal imaging and intravital multi-photon microscopy have proven invaluable, they provide limited insight into the architectural and structural context in which these responses occur. To interrogate the role of the lymph node environment in immune response effectively, a new set of imaging tools taking into account broader architectural context must be implemented into emerging immunological questions. METHODS AND RESULTS Using two different methods of whole-organ imaging, optical clearing and three-dimensional reconstruction of serially sectioned lymph nodes, fluorescent representations of whole lymph nodes can be acquired at cellular resolution. Using freely available post-processing tools, images of unlimited size and depth can be assembled into cohesive, contextual snapshots of immunological response. Through the implementation of robust iterative analysis techniques, these highly complex three-dimensional images can be objectified into sortable object data sets. These data can then be used to interrogate complex questions at the cellular level within the broader context of lymph node biology. CONCLUSIONS By combining existing imaging technology with complex methods of sample preparation and capture, we have developed efficient systems for contextualizing immunological phenomena within lymphatic architecture. In combination with robust approaches to image analysis, these advances provide a path to integrating scientific understanding of basic lymphatic biology into the complex nature of immunological response.
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Affiliation(s)
- Matthew C Woodruff
- 1 Graduate Program in Immunology, Harvard Medical School , Boston, Massachusetts
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204
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Ezrin is a component of the HIV-1 virological presynapse and contributes to the inhibition of cell-cell fusion. J Virol 2014; 88:7645-58. [PMID: 24760896 DOI: 10.1128/jvi.00550-14] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
UNLABELLED During cell-to-cell transmission of HIV-1, viral and cellular proteins transiently accumulate at the contact zone between infected (producer) and uninfected (target) cells, forming the virological synapse. Rearrangements of the cytoskeleton in producer and target cells are required for proper targeting of viral and cellular components during synapse formation, yet little is known about how these processes are regulated, particularly within the producer cell. Since ezrin-radixin-moesin (ERM) proteins connect F-actin with integral and peripheral membrane proteins, are incorporated into virions, and interact with cellular components of the virological presynapse, we hypothesized that they play roles during the late stage of HIV-1 replication. Here we document that phosphorylated (i.e., active) ezrin specifically accumulates at the HIV-1 presynapse in T cell lines and primary CD4(+) lymphocytes. To investigate whether ezrin supports virus transmission, we sought to ablate ezrin expression in producer cells. While cells did not tolerate a complete knockdown of ezrin, even a modest reduction of ezrin expression (~50%) in HIV-1-producing cells led to the release of particles with impaired infectivity. Further, when cocultured with uninfected target cells, ezrin-knockdown producer cells displayed reduced accumulation of the tetraspanin CD81 at the synapse and fused more readily with target cells, thus forming syncytia. Such an outcome likely is not optimal for virus dissemination, as evidenced by the fact that, in vivo, only relatively few infected cells form syncytia. Thus, ezrin likely helps secure efficient virus spread not only by enhancing virion infectivity but also by preventing excessive membrane fusion at the virological synapse. IMPORTANCE While viruses, in principal, can propagate through successions of syncytia, HIV-1-infected cells in the majority of cases do not fuse with potential target cells during viral transmission. This mode of spread is coresponsible for key features of HIV-1 pathogenesis, including killing of bystander cells and establishment of latently infected T lymphocytes. Here we identify the ERM protein family member ezrin as a cellular factor that contributes to the inhibition of cell-cell fusion and thus to suppressing excessive syncytium formation. Our analyses further suggest that ezrin, which connects integral membrane proteins with actin, functions in concert with CD81, a member of the tetraspanin family of proteins. Additional evidence, documented here and elsewhere, suggests that ezrin and CD81 cooperate to prevent cytoskeleton rearrangements that need to take place during the fusion of cellular membranes.
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205
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Barreto-de-Souza V, Arakelyan A, Margolis L, Vanpouille C. HIV-1 vaginal transmission: cell-free or cell-associated virus? Am J Reprod Immunol 2014; 71:589-99. [PMID: 24730358 DOI: 10.1111/aji.12240] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2014] [Accepted: 02/25/2014] [Indexed: 12/28/2022] Open
Abstract
The vast majority of new HIV infections in male-to-female transmission occurs through semen, where HIV-1 is present in two different forms: as free and as cell-associated virus. In the female lower genital tract, semen mixes with female genital secretions that contain various factors, some of which facilitate or inhibit HIV-1 transmission. Next, HIV-1 crosses the genital epithelia, reaches the regional lymph nodes, and disseminates through the female host. Cervico-vaginal mucosa contains multiple barriers, resulting in a low probability of vaginal transmission. However, in some cases, HIV-1 is able to break these barriers. Although the exact mechanisms of how these barriers function remain unclear, their levels of efficiency against cell-free and cell-associated HIV-1 are different, and both cell-free and cell-associated virions seem to use different strategies to overcome these barriers. Understanding the basic mechanisms of HIV-1 vaginal transmission is required for the development of new antiviral strategies to contain HIV-1 epidemics.
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Affiliation(s)
- Victor Barreto-de-Souza
- Section of Intercellular Interactions, Program in Physical Biology, Eunice Kennedy Shriver National Institute of Child Health and Human Development, Bethesda, MD, USA
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206
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Visualization and dynamic analysis of host-pathogen interactions. Curr Opin Immunol 2014; 29:8-15. [PMID: 24705104 DOI: 10.1016/j.coi.2014.03.002] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2014] [Revised: 03/05/2014] [Accepted: 03/06/2014] [Indexed: 12/15/2022]
Abstract
To contain invading microbes, the immune system must efficiently recognize the presence of the invader, mobilize cells to the site of infection, and deploy effector function. Rare antigen-specific T cells must find small numbers of antigen-presenting cells, proliferate and differentiate in secondary lymphoid tissues, then traffic to the infected site and be activated by antigen again to contribute to host defense. Our understanding of the dynamic processes involved has benefited enormously from tools that enable the visualization of cell location and behavior in complex tissue environments. Here we summarize recent insights into T cell trafficking and migration through secondary lymphoid organs and at peripheral infection sites, highlighting cell-intrinsic and extrinsic factors optimizing antigen surveillance at steady-state and delivery of an effector response during infection.
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207
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Angin M, Sharma S, King M, Murooka TT, Ghebremichael M, Mempel TR, Walker BD, Bhasin MK, Addo MM. HIV-1 infection impairs regulatory T-cell suppressive capacity on a per-cell basis. J Infect Dis 2014; 210:899-903. [PMID: 24664171 DOI: 10.1093/infdis/jiu188] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
The impact of CD4+ regulatory T cells (Tregs) on human immunodeficiency virus type 1 (HIV-1) pathogenesis remains incompletely understood. Although it has been shown that Tregs can be infected with HIV-1, the consequences of infection on a per-cell basis are still unknown. In vitro HIV-GFP infected and noninfected Tregs were isolated by flow-based cell-sorting to investigate Treg suppressive capacity and gene expression profiles. Our data show that HIV-1-infected Tregs were significantly less suppressive than noninfected Tregs and demonstrated down-regulation of genes critical to Treg function. This impaired function may have detrimental consequences for the control of generalized immune activation and accelerate HIV disease progression.
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Affiliation(s)
| | | | | | | | | | | | | | - Manoj K Bhasin
- BIDMC Genomics and Proteomics Center, Dana Farber/Harvard Cancer Center
| | - Marylyn M Addo
- Ragon Institute of MGH, MIT and Harvard Massachusetts General Hospital, Division of Infectious Diseases, Boston, Massachusetts Department of Medicine I, University Hospital Hamburg-Eppendorf German Center for Infection Research (DZIF), partner site Hamburg/Lübeck/Borstel, Germany
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208
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Symeonides M, Lambelé M, Roy NH, Thali M. Evidence showing that tetraspanins inhibit HIV-1-induced cell-cell fusion at a post-hemifusion stage. Viruses 2014; 6:1078-90. [PMID: 24608085 PMCID: PMC3970140 DOI: 10.3390/v6031078] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2014] [Revised: 02/14/2014] [Accepted: 02/20/2014] [Indexed: 02/07/2023] Open
Abstract
Human immunodeficiency virus type 1 (HIV-1) transmission takes place primarily through cell-cell contacts known as virological synapses. Formation of these transient adhesions between infected and uninfected cells can lead to transmission of viral particles followed by separation of the cells. Alternatively, the cells can fuse, thus forming a syncytium. Tetraspanins, small scaffolding proteins that are enriched in HIV-1 virions and actively recruited to viral assembly sites, have been found to negatively regulate HIV-1 Env-induced cell-cell fusion. How these transmembrane proteins inhibit membrane fusion, however, is currently not known. As a first step towards elucidating the mechanism of fusion repression by tetraspanins, e.g., CD9 and CD63, we sought to identify the stage of the fusion process during which they operate. Using a chemical epistasis approach, four fusion inhibitors were employed in tandem with CD9 overexpression. Cells overexpressing CD9 were found to be sensitized to inhibitors targeting the pre-hairpin and hemifusion intermediates, while they were desensitized to an inhibitor of the pore expansion stage. Together with the results of a microscopy-based dye transfer assay, which revealed CD9- and CD63-induced hemifusion arrest, our investigations strongly suggest that tetraspanins block HIV-1-induced cell-cell fusion at the transition from hemifusion to pore opening.
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Affiliation(s)
- Menelaos Symeonides
- Graduate Program in Cell and Molecular Biology, University of Vermont, Burlington, VT 05405, USA.
| | - Marie Lambelé
- Department of Microbiology and Molecular Genetics, University of Vermont, Burlington, VT 05405, USA.
| | - Nathan H Roy
- Graduate Program in Cell and Molecular Biology, University of Vermont, Burlington, VT 05405, USA.
| | - Markus Thali
- Graduate Program in Cell and Molecular Biology, University of Vermont, Burlington, VT 05405, USA.
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209
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Kiene M, Rethi B, Jansson M, Dillon S, Lee E, Lantto R, Wilson C, Pöhlmann S, Chiodi F. Toll-like receptor 3 signalling up-regulates expression of the HIV co-receptor G-protein coupled receptor 15 on human CD4+ T cells. PLoS One 2014; 9:e88195. [PMID: 24558379 PMCID: PMC3928197 DOI: 10.1371/journal.pone.0088195] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2013] [Accepted: 01/03/2014] [Indexed: 11/19/2022] Open
Abstract
Background Many HIV-2 and SIV isolates, as well as some HIV-1 strains, can use the orphan 7-transmembrane receptor GPR15 as co-receptor for efficient entry into host cells. GPR15 is expressed on central memory and effector memory CD4+ T cells in healthy individuals and a subset of these cells is susceptible to HIV-1 and SIV infection. However, it has not been determined whether GPR15 expression is altered in the context of HIV-1 infection. Results Here, we show that GPR15 expression in CD4+ T cells is markedly up-regulated in some HIV-1 infected individuals compared to the rest of the infected patients and to healthy controls. Infection of the PM1 T cell line with primary HIV-1 isolates was found to up-regulate GPR15 expression on the infected cells, indicating that viral components can induce GPR15 expression. Up-regulation of GPR15 expression on CD4+ T cells was induced by activation of Toll-like receptor 3 signalling via TIR-domain-containing adapter-inducing interferon-β (TRIF) and was more prominent on gut-homing compared to lymph node-homing CD4+ T cells. Conclusion These results suggest that infection-induced up-regulation of GPR15 expression could increase susceptibility of CD4+ T cells to HIV infection and target cell availability in the gut in some infected individuals.
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Affiliation(s)
- Miriam Kiene
- Institute of Virology, Hannover Medical School, Hannover, Germany
- Department of Microbiology, Tumor and Cell Biology, Karolinska Institutet, Stockholm, Sweden
| | - Bence Rethi
- Department of Microbiology, Tumor and Cell Biology, Karolinska Institutet, Stockholm, Sweden
| | - Marianne Jansson
- Department of Laboratory Medicine, Lund University, Lund, Sweden
| | - Stephanie Dillon
- Division of Infectious Diseases, University of Colorado Anschutz Medical Campus, Aurora, Colorado, United States of America
| | - Eric Lee
- Division of Infectious Diseases, University of Colorado Anschutz Medical Campus, Aurora, Colorado, United States of America
| | - Rebecka Lantto
- Department of Microbiology, Tumor and Cell Biology, Karolinska Institutet, Stockholm, Sweden
| | - Cara Wilson
- Division of Infectious Diseases, University of Colorado Anschutz Medical Campus, Aurora, Colorado, United States of America
| | - Stefan Pöhlmann
- Infection Biology Unit, German Primate Center, Göttingen, Germany
| | - Francesca Chiodi
- Department of Microbiology, Tumor and Cell Biology, Karolinska Institutet, Stockholm, Sweden
- * E-mail:
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210
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Foley MH, Forcier T, McAndrew E, Gonzalez M, Chen H, Juelg B, Walker BD, Irvine DJ. High avidity CD8+ T cells efficiently eliminate motile HIV-infected targets and execute a locally focused program of anti-viral function. PLoS One 2014; 9:e87873. [PMID: 24551068 PMCID: PMC3923750 DOI: 10.1371/journal.pone.0087873] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2013] [Accepted: 12/29/2013] [Indexed: 11/17/2022] Open
Abstract
The dissemination of HIV from an initial site of infection is facilitated by motile HIV-infected CD4+ T-cells. However, the impact of infected target cell migration on antigen recognition by HIV-specific CD8+ T-cells is unclear. Using a 3D in vitro model of tissue, we visualized dynamic interactions between HIV-infected or peptide-pulsed CD4+ T-cells and HIV-specific CD8+ T-cells. CTLs engaged motile HIV-infected targets, but ∼50% of targets broke contact and escaped. In contrast, immobilized target cells were readily killed, indicating target motility directly inhibits CD8+ T-cell function. Strong calcium signals occurred in CTLs killing a motile target but calcium signaling was weak or absent in CTLs which permitted target escape. Neutralization of adhesion receptors LFA-1 and CD58 inhibited CD8+ T-cell function within the 3D matrix, demonstrating that efficient motile target lysis as dependent on adhesive engagement of targets. Antigen sensitivity (a convolution of antigen density, TCR avidity and CD8 coreceptor binding) is also critical for target recognition. We modulated this parameter (known as functional avidity but referred to here as “avidity” for the sake of simplicity) by exploiting common HIV escape mutations and measured their impact on CTL function at the single-cell level. Targets pulsed with low avidity mutant antigens frequently escaped while CTLs killed targets bearing high avidity antigen with near-perfect efficiency. CTLs engaged, arrested, and killed an initial target bearing high avidity antigen within minutes, but serial killing was surprisingly rare. CD8 cells remained committed to their initial dead target for hours, accumulating TCR signals that sustained secretion of soluble antiviral factors. These data indicate that high-avidity CD8+ T-cells execute an antiviral program in the precise location where antigen has been sensed: CTL effector functions are spatiotemporally coordinated with an early lytic phase followed by a sustained stationary secretory phase to control local viral infection.
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Affiliation(s)
- Maria Hottelet Foley
- Department of Biological Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States of America ; Ragon Institute of Massachusetts General Hospital, Massachusetts Institute of Technology, and Harvard University, Cambridge, Massachusetts, United States of America ; Koch Institute for Integrative Cancer Research, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States of America
| | - Talitha Forcier
- Ragon Institute of Massachusetts General Hospital, Massachusetts Institute of Technology, and Harvard University, Cambridge, Massachusetts, United States of America ; Department of Material Science and Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States of America
| | - Elizabeth McAndrew
- Ragon Institute of Massachusetts General Hospital, Massachusetts Institute of Technology, and Harvard University, Cambridge, Massachusetts, United States of America
| | - Michael Gonzalez
- Howard Hughes Medical Institute, Chevy Chase, Maryland, United States of America
| | - Huabiao Chen
- Ragon Institute of Massachusetts General Hospital, Massachusetts Institute of Technology, and Harvard University, Cambridge, Massachusetts, United States of America
| | - Boris Juelg
- Ragon Institute of Massachusetts General Hospital, Massachusetts Institute of Technology, and Harvard University, Cambridge, Massachusetts, United States of America
| | - Bruce D Walker
- Ragon Institute of Massachusetts General Hospital, Massachusetts Institute of Technology, and Harvard University, Cambridge, Massachusetts, United States of America ; Howard Hughes Medical Institute, Chevy Chase, Maryland, United States of America
| | - Darrell J Irvine
- Department of Biological Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States of America ; Ragon Institute of Massachusetts General Hospital, Massachusetts Institute of Technology, and Harvard University, Cambridge, Massachusetts, United States of America ; Koch Institute for Integrative Cancer Research, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States of America ; Department of Material Science and Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States of America ; Howard Hughes Medical Institute, Chevy Chase, Maryland, United States of America
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211
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Agosto LM, Zhong P, Munro J, Mothes W. Highly active antiretroviral therapies are effective against HIV-1 cell-to-cell transmission. PLoS Pathog 2014; 10:e1003982. [PMID: 24586176 PMCID: PMC3937346 DOI: 10.1371/journal.ppat.1003982] [Citation(s) in RCA: 78] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2013] [Accepted: 01/22/2014] [Indexed: 11/30/2022] Open
Abstract
HIV-1 cell-to-cell transmission allows for 2-3 orders of magnitude more efficient viral spread than cell-free dissemination. The high local multiplicity of infection (MOI) observed at cell-cell contact sites may lower the efficacy of antiretroviral therapies (ART). Here we test the efficacy of commonly used antiretroviral inhibitors against cell-to-cell and cell-free HIV-1 transmission. We demonstrate that, while some nucleoside-analog reverse transcriptase inhibitors (NRTI) are less effective against HIV-1 cell-to-cell transmission, most non-nucleoside-analog reverse transcriptase inhibitors (NNRTI), entry inhibitors and protease inhibitors remain highly effective. Moreover, poor NRTIs become highly effective when applied in combinations explaining the effectiveness of ART in clinical settings. Investigating the underlying mechanism, we observe a strict correlation between the ability of individual drugs and combinations of drugs to interfere with HIV-1 cell-to-cell transmission, and their effectiveness against high viral MOIs. Our results suggest that the ability to suppress high viral MOI is a feature of effective ART regimens and this parameter should be considered when designing novel antiviral therapies.
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Affiliation(s)
- Luis M. Agosto
- Department of Microbial Pathogenesis, Yale University School of Medicine, New Haven, Connecticut, United States of America
| | - Peng Zhong
- Department of Microbial Pathogenesis, Yale University School of Medicine, New Haven, Connecticut, United States of America
| | - James Munro
- Department of Microbial Pathogenesis, Yale University School of Medicine, New Haven, Connecticut, United States of America
| | - Walther Mothes
- Department of Microbial Pathogenesis, Yale University School of Medicine, New Haven, Connecticut, United States of America
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212
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Claser C, Malleret B, Peng K, Bakocevic N, Gun SY, Russell B, Ng LG, Rénia L. Rodent Plasmodium-infected red blood cells: Imaging their fates and interactions within their hosts. Parasitol Int 2014; 63:187-94. [DOI: 10.1016/j.parint.2013.07.012] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2013] [Revised: 06/30/2013] [Accepted: 07/15/2013] [Indexed: 10/26/2022]
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213
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Wilson EMP, Sereti I. Immune restoration after antiretroviral therapy: the pitfalls of hasty or incomplete repairs. Immunol Rev 2014; 254:343-54. [PMID: 23772630 DOI: 10.1111/imr.12064] [Citation(s) in RCA: 106] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Antiretroviral therapy (ART) is a life-saving intervention in human immunodeficiency virus (HIV) infection. Immune restoration after ART dramatically reduces the incidence and severity of opportunistic diseases and death. On some occasions, immune restoration may be erratic, leading to acute inflammatory responses (known as immune reconstitution inflammatory syndrome) shortly after ART initiation, or incomplete, with residual inflammation despite chronic treatment, leading to non-infectious morbidity and mortality. We propose that ART may not always restore the perfect balance of innate and adaptive immunity in strategic milieus, predisposing HIV-infected persons to complications of acute or chronic inflammation. The best current strategy for fully successful immune restoration is early antiretroviral therapy, which can prevent acquired immunodeficiency syndrome (AIDS)-associated events, restrict cell subset imbalances and dysfunction, while preserving structural integrity of lymphoid tissues. Future HIV research should capitalize on innovative techniques and move beyond the static study of T-cell subsets in peripheral blood or isolated tissues. Improved targeted therapeutic strategies could stem from a better understanding of how HIV perturbs the environmental niches and the mobility and trafficking of cells that affect the dynamic cell-to-cell interactions and determine the outcome of innate and adaptive immune responses.
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Affiliation(s)
- Eleanor M P Wilson
- HIV Pathogenesis Unit, Laboratory of Immunoregulation, NIAID/NIH, Bethesda, MD, USA
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214
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Kulpa DA, Brehm JH, Fromentin R, Cooper A, Cooper C, Ahlers J, Chomont N, Sékaly RP. The immunological synapse: the gateway to the HIV reservoir. Immunol Rev 2014; 254:305-25. [PMID: 23772628 PMCID: PMC3707302 DOI: 10.1111/imr.12080] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
A major challenge in the development of a cure for human immunodeficiency virus (HIV) has been the incomplete understanding of the basic mechanisms underlying HIV persistence during antiretroviral therapy. It is now realized that the establishment of a latently infected reservoir refractory to immune system recognition has thus far hindered eradication efforts. Recent investigation into the innate immune response has shed light on signaling pathways downstream of the immunological synapse critical for T-cell activation and establishment of T-cell memory. This has led to the understanding that the cell-to-cell contacts observed in an immunological synapse that involve the CD4+ T cell and antigen-presenting cell or T-cell–T-cell interactions enhance efficient viral spread and facilitate the induction and maintenance of latency in HIV-infected memory T cells. This review focuses on recent work characterizing the immunological synapse and the signaling pathways involved in T-cell activation and gene regulation in the context of HIV persistence.
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Affiliation(s)
- Deanna A Kulpa
- Division of Infectious Diseases, Vaccine and Gene Therapy Institute-Florida (VGTI-FL), Port Saint Lucie, FL 34987, USA
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215
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Torres-Castro I, Cortés-Rubio CN, Sandoval G, Lamoyi E, Larralde C, Huerta L. Flow cytometry analysis of cell population dynamics and cell cycle during HIV-1 envelope-mediated formation of syncytia in vitro. In Vitro Cell Dev Biol Anim 2014; 50:453-63. [DOI: 10.1007/s11626-013-9724-z] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2013] [Accepted: 12/09/2013] [Indexed: 02/01/2023]
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216
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Covassin L, Jangalwe S, Jouvet N, Laning J, Burzenski L, Shultz LD, Brehm MA. Human immune system development and survival of non-obese diabetic (NOD)-scid IL2rγ(null) (NSG) mice engrafted with human thymus and autologous haematopoietic stem cells. Clin Exp Immunol 2014; 174:372-88. [PMID: 23869841 DOI: 10.1111/cei.12180] [Citation(s) in RCA: 90] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 07/12/2013] [Indexed: 01/01/2023] Open
Abstract
Immunodeficient mice bearing targeted mutations in the IL2rg gene and engrafted with human immune systems are effective tools for the study of human haematopoiesis, immunity, infectious disease and transplantation biology. The most robust human immune model is generated by implantation of human fetal thymic and liver tissues in irradiated recipients followed by intravenous injection of autologous fetal liver haematopoietic stem cells [often referred to as the BLT (bone marrow, liver, thymus) model]. To evaluate the non-obese diabetic (NOD)-scid IL2rγ(null) (NSG)-BLT model, we have assessed various engraftment parameters and how these parameters influence the longevity of NSG-BLT mice. We observed that irradiation and subrenal capsule implantation of thymus/liver fragments was optimal for generating human immune systems. However, after 4 months, a high number of NSG-BLT mice develop a fatal graft-versus-host disease (GVHD)-like syndrome, which correlates with the activation of human T cells and increased levels of human immunoglobulin (Ig). Onset of GVHD was not delayed in NSG mice lacking murine major histocompatibility complex (MHC) classes I or II and was not associated with a loss of human regulatory T cells or absence of intrathymic cells of mouse origin (mouse CD45(+) ). Our findings demonstrate that NSG-BLT mice develop robust human immune systems, but that the experimental window for these mice may be limited by the development of GVHD-like pathological changes.
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Affiliation(s)
- L Covassin
- Department of Molecular Medicine, University of Massachusetts Medical School, Worcester, MA, USA
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217
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Blood, sphingosine-1-phosphate and lymphocyte migration dynamics in the spleen. Curr Top Microbiol Immunol 2014; 378:107-28. [PMID: 24728595 DOI: 10.1007/978-3-319-05879-5_5] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
The spleen, the largest secondary lymphoid organ, has long been known to play important roles in immunity against blood-borne invaders. Yet how cells migrate within the spleen to ensure fast and effective responses is only now coming to light. Chemokines and oxysterols guide lymphocytes from sites of release at terminal arterioles into the lymphocyte-rich white pulp. Sphingosine-1-phosphate (S1P) and S1P-receptor-1 (S1PR1) promote lymphocyte egress from white to red pulp and back to circulation. Intravital two-photon microscopy has shown that marginal zone (MZ) B cells that are enriched between white and red pulps undergo continual oscillatory migration between the MZ and follicles, ferrying antigens. Cycles of G-protein-coupled receptor kinase-2 (GRK2) mediated S1PR1 desensitization and resensitization underlie this remarkable behavior. The findings discussed in this review have implications for understanding how splenic antibody and T-cell responses are mounted, how the immunosuppressant drug FTY720 (fingolimod) affects the spleen, and how cell shuttling behaviors contribute to immunity.
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218
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Spatial modeling of HIV cryptic viremia and 2-LTR formation during raltegravir intensification. J Theor Biol 2013; 345:61-9. [PMID: 24378646 DOI: 10.1016/j.jtbi.2013.12.020] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2013] [Revised: 10/31/2013] [Accepted: 12/16/2013] [Indexed: 11/21/2022]
Abstract
Combination Antiretroviral Therapy (cART) can suppress plasma HIV below the limit of detection in normal assays. Recently reported results suggest that viral replication may continue in some patients, despite undetectable levels in the blood. It has been suggested that the appearance of the circularized episomal HIV DNA artifact 2-LTR following treatment intensification with the integrase inhibitor raltegravir is a marker of ongoing viral replication. Other work has suggested that lymphoid organs may be a site of reduced antiviral penetration and increased viral production. In this study we model the hypothesis that this ongoing replication occurs in lymphoid follicle sanctuary sites and investigate the patterns of 2-LTR formation expected after raltegravir application. Experimental data is used to estimate the reaction and diffusion parameters in the model, and Monte-Carlo simulations are used to explore model behavior subject to variation in these rates. The results suggest that conditions for the formation of an observed transient peak in 2-LTR formation following raltegravir intensification include a sanctuary site diameter larger than 0.2mm, a viral basic reproductive ratio within the site larger than 1, and a total volume of active sanctuary sites above 20mL. Significant levels of uncontrolled replication can occur in the sanctuary sites without measurable changes in the plasma viral load. By contrast, subcritical replication (where the basic reproductive ratio of the virus is less than 1 in all sites) always results in monotonic increases of measured 2-LTR following raltegravir intensification, occurring at levels below the limit of detection.
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219
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Titanji BK, Aasa-Chapman M, Pillay D, Jolly C. Protease inhibitors effectively block cell-to-cell spread of HIV-1 between T cells. Retrovirology 2013; 10:161. [PMID: 24364896 PMCID: PMC3877983 DOI: 10.1186/1742-4690-10-161] [Citation(s) in RCA: 62] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2013] [Accepted: 12/11/2013] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND The Human Immunodeficiency Virus type-1 (HIV-1) spreads by cell-free diffusion and by direct cell-to-cell transfer, the latter being a significantly more efficient mode of transmission. Recently it has been suggested that cell-to-cell spread may permit ongoing virus replication in the presence of antiretroviral therapy (ART) based on studies performed using Reverse Transcriptase Inhibitors (RTIs). Protease Inhibitors (PIs) constitute an important component of ART; however whether this class of inhibitors can suppress cell-to-cell transfer of HIV-1 is unexplored. Here we have evaluated the inhibitory effect of PIs during cell-to-cell spread of HIV-1 between T lymphocytes. RESULTS Using quantitative assays in cell line and primary cell systems that directly measure the early steps of HIV-1 infection we find that the PIs Lopinavir and Darunavir are equally potent against both cell-free and cell-to-cell spread of HIV-1. We further show that a protease resistant mutant maintains its resistant phenotype during cell-to-cell spread and is transmitted more efficiently than wild-type virus in the presence of drug. By contrast we find that T cell-T cell spread of HIV-1 is 4-20 fold more resistant to inhibition by the RTIs Nevirapine, Zidovudine and Tenofovir. Notably, varying the ratio of infected and uninfected cells in co-culture impacted on the degree of inhibition, indicating that the relative efficacy of ART is dependent on the multiplicity of infection. CONCLUSIONS We conclude that if the variable effects of antiviral drugs on cell-to-cell virus dissemination of HIV-1 do indeed impact on viral replication and maintenance of viral reservoirs this is likely to be influenced by the antiviral drug class, since PIs appear particularly effective against both modes of HIV-1 spread.
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Affiliation(s)
| | | | | | - Clare Jolly
- Division of Infection and Immunity, University College London, Cruciform Building, Gower St, London WC1E 6BT, United Kingdom.
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High-multiplicity HIV-1 infection and neutralizing antibody evasion mediated by the macrophage-T cell virological synapse. J Virol 2013; 88:2025-34. [PMID: 24307588 DOI: 10.1128/jvi.03245-13] [Citation(s) in RCA: 88] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Macrophage infection is considered to play an important role in HIV-1 pathogenesis and persistence. Using a primary cell-based coculture model, we show that monocyte-derived macrophages (MDM) efficiently transmit a high-multiplicity HIV-1 infection to autologous CD4(+) T cells through a viral envelope glycoprotein (Env) receptor- and actin-dependent virological synapse (VS), facilitated by interactions between ICAM-1 and LFA-1. Virological synapse (VS)-mediated transmission by MDM results in high levels of T cell HIV-1 integration and is 1 to 2 orders of magnitude more efficient than cell-free infection. This mode of cell-to-cell transmission is broadly susceptible to the activity of CD4 binding site (CD4bs) and glycan or glycopeptide epitope-specific broadly neutralizing monoclonal antibodies (bNMAbs) but shows resistance to bNMAbs targeting the Env gp41 subunit membrane-proximal external region (MPER). These data define for the first time the structure and function of the macrophage-to-T cell VS and have important implications for bNMAb activity in HIV-1 prophylaxis and therapy. IMPORTANCE The ability of HIV-1 to move directly between contacting immune cells allows efficient viral dissemination with the potential to evade antibody attack. Here, we show that HIV-1 spreads from infected macrophages to T cells via a structure called a virological synapse that maintains extended contact between the two cell types, allowing transfer of multiple infectious events to the T cell. This process allows the virus to avoid neutralization by a class of antibody targeting the gp41 subunit of the envelope glycoproteins. These results have implications for viral spread in vivo and the specificities of neutralizing antibody elicited by antibody-based vaccines.
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221
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Malbec M, Porrot F, Rua R, Horwitz J, Klein F, Halper-Stromberg A, Scheid JF, Eden C, Mouquet H, Nussenzweig MC, Schwartz O. Broadly neutralizing antibodies that inhibit HIV-1 cell to cell transmission. ACTA ACUST UNITED AC 2013; 210:2813-21. [PMID: 24277152 PMCID: PMC3865481 DOI: 10.1084/jem.20131244] [Citation(s) in RCA: 139] [Impact Index Per Article: 12.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
A subset of broadly neutralizing anti-HIV antibodies inhibits cell to cell transmission of the virus. The neutralizing activity of anti–HIV-1 antibodies is typically measured in assays where cell-free virions enter reporter cell lines. However, HIV-1 cell to cell transmission is a major mechanism of viral spread, and the effect of the recently described broadly neutralizing antibodies (bNAbs) on this mode of transmission remains unknown. Here we identify a subset of bNAbs that inhibit both cell-free and cell-mediated infection in primary CD4+ lymphocytes. These antibodies target either the CD4-binding site (NIH45-46 and 3BNC60) or the glycan/V3 loop (10-1074 and PGT121) on HIV-1 gp120 and act at low concentrations by inhibiting multiple steps of viral cell to cell transmission. These antibodies accumulate at virological synapses and impair the clustering and fusion of infected and target cells and the transfer of viral material to uninfected T cells. In addition, they block viral cell to cell transmission to plasmacytoid DCs and thereby interfere with type-I IFN production. Thus, only a subset of bNAbs can efficiently prevent HIV-1 cell to cell transmission, and this property should be considered an important characteristic defining antibody potency for therapeutic or prophylactic antiviral strategies.
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Affiliation(s)
- Marine Malbec
- Virus and Immunity Unit, Department of Virology; and 2 Laboratory of Humoral Response to Pathogens, Department of Immunology; Institut Pasteur, 75015 Paris, France
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222
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Sherer NM. Long-distance relationships: do membrane nanotubes regulate cell-cell communication and disease progression? Mol Biol Cell 2013; 24:1095-8. [PMID: 23580190 PMCID: PMC3623630 DOI: 10.1091/mbc.e12-08-0622] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Metazoan cells rapidly exchange signals at tight cell-cell interfaces, including synapses and gap junctions. Advances in imaging recently exposed a third mode of intercellular cross-talk mediated by thin, actin-containing membrane extensions broadly known as "membrane" or "tunneling" nanotubes. An explosion of research suggests diverse functions for nanotubular superhighways, including cell-cell electrical coupling, calcium signaling, small-molecule exchange, and, remarkably, the transfer of bulky cargoes, including organelles or pathogenic agents. Despite great enthusiasm for all things nanotubular and their potential roles in cell signaling and pathogenesis, key questions remain regarding the mechanisms by which these structures regulate directional cell-cell exchange; how these linkages are formed and between which cells and, critically, whether nanotubes are as prevalent in vivo as they appear to be in the incubator.
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Affiliation(s)
- Nathan M Sherer
- McArdle Laboratory for Cancer Research, Institute for Molecular Virology, and Carbone Cancer Center, School of Medicine and Public Health, University of Wisconsin-Madison, Madison, WI 53706, USA.
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223
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Watkins RL, Zou W, Denton PW, Krisko JF, Foster JL, Garcia JV. In vivo analysis of highly conserved Nef activities in HIV-1 replication and pathogenesis. Retrovirology 2013; 10:125. [PMID: 24172637 PMCID: PMC3907037 DOI: 10.1186/1742-4690-10-125] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2013] [Accepted: 10/23/2013] [Indexed: 12/31/2022] Open
Abstract
BACKGROUND The HIV-1 accessory protein, Nef, is decisive for progression to AIDS. In vitro characterization of the protein has described many Nef activities of unknown in vivo significance including CD4 downregulation and a number of activities that depend on Nef interacting with host SH3 domain proteins. Here, we use the BLT humanized mouse model of HIV-1 infection to assess their impact on viral replication and pathogenesis and the selection pressure to restore these activities using enforced in vivo evolution. RESULTS We followed the evolution of HIV-1LAI (LAI) with a frame-shifted nef (LAINeffs) during infection of BLT mice. LAINeffs was rapidly replaced in blood by virus with short deletions in nef that restored the open reading frame (LAINeffs∆-1 and LAINeffs∆-13). Subsequently, LAINeffs∆-1 was often replaced by wild type LAI. Unexpectedly, LAINeffs∆-1 and LAINeffs∆-13 Nefs were specifically defective for CD4 downregulation activity. Viruses with these mutant nefs were used to infect BLT mice. LAINeffs∆-1 and LAINeffs∆-13 exhibited three-fold reduced viral replication (compared to LAI) and a 50% reduction of systemic CD4+ T cells (>90% for LAI) demonstrating the importance of CD4 downregulation. These results also demonstrate that functions other than CD4 downregulation enhanced viral replication and pathogenesis of LAINeffs∆-1 and LAINeffs∆-13 compared to LAINeffs. To gain insight into the nature of these activities, we constructed the double mutant P72A/P75A. Multiple Nef activities can be negated by mutating the SH3 domain binding site (P72Q73V74P75L76R77) to P72A/P75A and this mutation does not affect CD4 downregulation. Virus with nef mutated to P72A/P75A closely resembled the wild-type virus in vivo as viral replication and pathogenesis was not significantly altered. Unlike LAINeffs described above, the P72A/P75A mutation had a very weak tendency to revert to wild type sequence. CONCLUSIONS The in vivo phenotype of Nef is significantly dependent on CD4 downregulation but minimally on the numerous Nef activities that require an intact SH3 domain binding motif. These results suggest that CD4 downregulation plus one or more unknown Nef activities contribute to enhanced viral replication and pathogenesis and are suitable targets for anti-HIV therapy. Enforced evolution studies in BLT mice will greatly facilitate identification of these critical activities.
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Affiliation(s)
- Richard L Watkins
- Division of Infectious Diseases, Center for AIDS Research, 2042 Genetic Medicine, University of North Carolina, Campus Box 7042, Chapel Hill, NC 27599-7042, USA.
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Watkins RL, Zou W, Denton PW, Krisko JF, Foster JL, Garcia JV. In vivo analysis of highly conserved Nef activities in HIV-1 replication and pathogenesis. Retrovirology 2013. [PMID: 24172637 DOI: 10.1186/742-4690-10-125] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/03/2023] Open
Abstract
BACKGROUND The HIV-1 accessory protein, Nef, is decisive for progression to AIDS. In vitro characterization of the protein has described many Nef activities of unknown in vivo significance including CD4 downregulation and a number of activities that depend on Nef interacting with host SH3 domain proteins. Here, we use the BLT humanized mouse model of HIV-1 infection to assess their impact on viral replication and pathogenesis and the selection pressure to restore these activities using enforced in vivo evolution. RESULTS We followed the evolution of HIV-1LAI (LAI) with a frame-shifted nef (LAINeffs) during infection of BLT mice. LAINeffs was rapidly replaced in blood by virus with short deletions in nef that restored the open reading frame (LAINeffs∆-1 and LAINeffs∆-13). Subsequently, LAINeffs∆-1 was often replaced by wild type LAI. Unexpectedly, LAINeffs∆-1 and LAINeffs∆-13 Nefs were specifically defective for CD4 downregulation activity. Viruses with these mutant nefs were used to infect BLT mice. LAINeffs∆-1 and LAINeffs∆-13 exhibited three-fold reduced viral replication (compared to LAI) and a 50% reduction of systemic CD4+ T cells (>90% for LAI) demonstrating the importance of CD4 downregulation. These results also demonstrate that functions other than CD4 downregulation enhanced viral replication and pathogenesis of LAINeffs∆-1 and LAINeffs∆-13 compared to LAINeffs. To gain insight into the nature of these activities, we constructed the double mutant P72A/P75A. Multiple Nef activities can be negated by mutating the SH3 domain binding site (P72Q73V74P75L76R77) to P72A/P75A and this mutation does not affect CD4 downregulation. Virus with nef mutated to P72A/P75A closely resembled the wild-type virus in vivo as viral replication and pathogenesis was not significantly altered. Unlike LAINeffs described above, the P72A/P75A mutation had a very weak tendency to revert to wild type sequence. CONCLUSIONS The in vivo phenotype of Nef is significantly dependent on CD4 downregulation but minimally on the numerous Nef activities that require an intact SH3 domain binding motif. These results suggest that CD4 downregulation plus one or more unknown Nef activities contribute to enhanced viral replication and pathogenesis and are suitable targets for anti-HIV therapy. Enforced evolution studies in BLT mice will greatly facilitate identification of these critical activities.
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Affiliation(s)
- Richard L Watkins
- Division of Infectious Diseases, Center for AIDS Research, 2042 Genetic Medicine, University of North Carolina, Campus Box 7042, Chapel Hill, NC 27599-7042, USA.
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Schiffner T, Sattentau QJ, Duncan CJA. Cell-to-cell spread of HIV-1 and evasion of neutralizing antibodies. Vaccine 2013; 31:5789-97. [PMID: 24140477 DOI: 10.1016/j.vaccine.2013.10.020] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2013] [Revised: 09/29/2013] [Accepted: 10/04/2013] [Indexed: 01/13/2023]
Abstract
Cell-to-cell spread of human immunodeficiency virus (HIV-1) between immune cells was first observed over 20 years ago. During this time, the question of whether this infection route favours viral evasion of neutralizing antibodies (NAbs) targeting the virus envelope glycoprotein (Env) has been repeatedly investigated, but with conflicting results. A clearer picture has formed in the last few years as more broadly neutralizing antibodies have been isolated and we gain further insight into the mechanisms of HIV-1 transmission at virological and infectious synapses. Nevertheless consensus is still lacking, a situation which may be at least partly explained by variability in the experimental approaches used to study the activity of NAbs in the cell-to-cell context. In this review we focus on the most critical question concerning the activity of NAbs against cell-to-cell transmission: is NAb inhibition of cell-to-cell HIV-1 quantitatively or qualitatively different from cell-free infection? Overall, data consistently show that NAbs are capable of blocking HIV-1 infection at synapses, supporting the concept that cell-to-cell infection occurs through directed transfer of virions accessible to the external environment. However, more recent findings suggest that higher concentrations of certain NAbs might be needed to inhibit synaptic infection, with important potential implications for prophylactic vaccine development. We discuss several mechanistic explanations for this relative and selective loss of activity, and highlight gaps in knowledge that are still to be explored.
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Affiliation(s)
- Torben Schiffner
- Sir William Dunn School of Pathology, University of Oxford, South Parks Road, Oxford OX1 3RE, United Kingdom
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226
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Gaudin R, de Alencar BC, Arhel N, Benaroch P. HIV trafficking in host cells: motors wanted! Trends Cell Biol 2013; 23:652-62. [PMID: 24119663 DOI: 10.1016/j.tcb.2013.09.004] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2013] [Revised: 09/05/2013] [Accepted: 09/09/2013] [Indexed: 11/16/2022]
Abstract
Throughout the viral replication cycle, viral proteins, complexes, and particles need to be transported within host cells. These transport events are dependent on the host cell cytoskeleton and molecular motors. However, the mechanisms by which virus is trafficked along cytoskeleton filaments and how molecular motors are recruited and regulated to guarantee successful integration of the viral genome and production of new viruses has only recently begun to be understood. Recent studies on HIV have identified specific molecular motors involved in the trafficking of these viral particles. Here we review recent literature on the transport of HIV components in the cell, provide evidence for the identity and role of molecular motors in this process, and highlight how these trafficking events may be related to those occurring with other viruses.
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Affiliation(s)
- Raphaël Gaudin
- Institut Curie, Centre de Recherche, 26 rue d'Ulm, 75248 Paris Cedex 05, France; INSERM, U932, 26 rue d'Ulm, 75248 Paris Cedex 05, France
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227
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Lafouresse F, Vasconcelos Z, Cotta-de-Almeida V, Dupré L. Actin cytoskeleton control of the comings and goings of T lymphocytes. ACTA ACUST UNITED AC 2013; 82:301-11. [PMID: 24131017 DOI: 10.1111/tan.12193] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
T lymphocytes are key players of adaptive immune responses. Upon recognition of specific peptides presented by human leukocyte antigen (HLA) molecules on antigen presenting cells (APC), these cells execute subset-related functions such as killing, help and regulation. The ontogeny, the activation and the effector functions of T lymphocytes are all steps of T-lymphocyte life cycle that rely on high motility properties. These cells travel through the organism in a succession of steps, including entry into tissues, interstitial migration, APC scanning, synapse formation and tissue exit. Such ability is possible because of a plastic motility behavior, which is highly controlled in time and space. The molecular basis for the adaptable motility behavior of T lymphocytes is only starting to be unraveled. The scope of this review is to discuss recent data pointing to the key role of regulators of actin cytoskeleton remodeling in tuning distinct aspects of T-lymphocyte motility during their entry, residency and exit from tissues.
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Affiliation(s)
- F Lafouresse
- INSERM, U1043, Toulouse, France; Centre de Physiopathologie de Toulouse Purpan, Université Toulouse III Paul-Sabatier, Toulouse, France; CNRS, U5282, Toulouse, France
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228
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In vivo imaging in NHP models of malaria: challenges, progress and outlooks. Parasitol Int 2013; 63:206-15. [PMID: 24042056 PMCID: PMC7108422 DOI: 10.1016/j.parint.2013.09.001] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2012] [Revised: 08/30/2013] [Accepted: 09/06/2013] [Indexed: 12/22/2022]
Abstract
Animal models of malaria, mainly mice, have made a large contribution to our knowledge of host-pathogen interactions and immune responses, and to drug and vaccine design. Non-human primate (NHP) models for malaria are admittedly under-used, although they are probably closer models than mice for human malaria; in particular, NHP models allow the use of human pathogens (Plasmodium falciparum, Plasmodium vivax, Plasmodium malariae and Plasmodium knowlesi). NHPs, whether natural hosts or experimentally challenged with a simian Plasmodium, can also serve as robust pre-clinical models. Some simian parasites are closely related to a human counterpart, with which they may share a common ancestor, and display similar major features with the human infection and pathology. NHP models allow longitudinal studies, from the early events following sporozoite inoculation to the later events, including analysis of organs and tissues, particularly liver, spleen, brain and bone marrow. NHP models have one other significant advantage over mouse models: NHPs are our closest relatives and thus their biology is very similar to ours. Recently developed in vivo imaging tools have provided insight into malaria parasite infection and disease in mouse models. One advantage of these tools is that they limit the need for invasive procedures, such as tissue biopsies. Many such technologies are now available for NHP studies and provide new opportunities for elucidating host/parasite interactions. The aim of this review is to bring the malaria community up to date on what is currently possible and what soon will be, in terms of in vivo imaging in NHP models of malaria, to consider the pros and the cons of the various techniques, and to identify challenges.
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Duncan CJ, Russell RA, Sattentau QJ. High multiplicity HIV-1 cell-to-cell transmission from macrophages to CD4+ T cells limits antiretroviral efficacy. AIDS 2013; 27:2201-6. [PMID: 24005480 PMCID: PMC4714465 DOI: 10.1097/qad.0b013e3283632ec4] [Citation(s) in RCA: 60] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
OBJECTIVE Few studies have examined the efficacy of antiretroviral therapy (ART) in the context of cell-to-cell transmission. We aimed to determine whether the activity of ART is limited by the mode of HIV-1 spread between cells and the type of immune cell implicated in transmission, or is independent of these variables. DESIGN ART activity was evaluated in primary cells using in-vitro cell-free and cell to-cell HIV-1 infection systems. METHODS HIV-1 cell-free or cell-to-cell transmission between infected monocyte-derived macrophages (MDMs) and autologous target CD4+ T cells was measured in the presence or absence of reverse transcriptase and integrase inhibitors. Viral infection was evaluated using luciferase-reporter infectious molecular HIV-1 clones carrying macrophage-tropic envelope glycoproteins (Envs). Cell-free HIV-1 was titrated to yield different multiplicities of CD4+ T-cell infection. RESULTS Whereas cell-free infection of CD4+ T cells was substantially reduced by all inhibitors, cell-to-cell spread from macrophages to CD4+ T cells was largely resistant to inhibition. However, when multiplicity of infection was controlled for, we observed no difference in antiretroviral inhibition of cell-to-cell or cell-free infection. CONCLUSION Cell-to-cell spread of HIV-1 reduces the probability of antiretroviral inhibition, but it is the number of infectious viruses transferred between cells rather than the specific mode of viral spread or transmitting cell type that governs antiretroviral activity. High multiplicity infection in vivo is more likely to occur by cell-to-cell transmission, and these data will inform use of ART against viral reservoirs.
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Affiliation(s)
- Christopher J.A. Duncan
- Sir William Dunn School of Pathology, University of Oxford, South Parks Road, Oxford OX1 3RE, United Kingdom
| | - Rebecca A. Russell
- Sir William Dunn School of Pathology, University of Oxford, South Parks Road, Oxford OX1 3RE, United Kingdom
| | - Quentin J. Sattentau
- Sir William Dunn School of Pathology, University of Oxford, South Parks Road, Oxford OX1 3RE, United Kingdom
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Palha N, Guivel-Benhassine F, Briolat V, Lutfalla G, Sourisseau M, Ellett F, Wang CH, Lieschke GJ, Herbomel P, Schwartz O, Levraud JP. Real-time whole-body visualization of Chikungunya Virus infection and host interferon response in zebrafish. PLoS Pathog 2013; 9:e1003619. [PMID: 24039582 PMCID: PMC3764224 DOI: 10.1371/journal.ppat.1003619] [Citation(s) in RCA: 129] [Impact Index Per Article: 11.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2013] [Accepted: 07/29/2013] [Indexed: 12/23/2022] Open
Abstract
Chikungunya Virus (CHIKV), a re-emerging arbovirus that may cause severe disease, constitutes an important public health problem. Herein we describe a novel CHIKV infection model in zebrafish, where viral spread was live-imaged in the whole body up to cellular resolution. Infected cells emerged in various organs in one principal wave with a median appearance time of ∼14 hours post infection. Timing of infected cell death was organ dependent, leading to a shift of CHIKV localization towards the brain. As in mammals, CHIKV infection triggered a strong type-I interferon (IFN) response, critical for survival. IFN was mainly expressed by neutrophils and hepatocytes. Cell type specific ablation experiments further demonstrated that neutrophils play a crucial, unexpected role in CHIKV containment. Altogether, our results show that the zebrafish represents a novel valuable model to dynamically visualize replication, pathogenesis and host responses to a human virus. Chikungunya, a re-emerging disease caused by a mosquito-transmitted virus, is an important public health problem. We developed a zebrafish model for chikungunya virus infection. For the first time, rise and death of virus-infected cells could be live imaged in the entire body of a vertebrate. We observed a widespread wave of apparition of newly infected cells during the first day after inoculation of the virus. We then found that infected cells died at a strongly organ-dependent rate, accounting for the progressive shift of virus localization. Notably, the virus persisted in the brain despite apparent recovery of infected zebrafish. We found this recovery to be critically dependent on the host type I interferon response. Surprisingly, we identified neutrophils as a major cell population expressing interferon and controlling chikungunya virus.
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Affiliation(s)
- Nuno Palha
- Institut Pasteur, Macrophages et Développement de l'Immunité, Department of Developmental and Stem Cells Biology, Paris, France
- CNRS URA2578, Paris, France
- Université Pierre et Marie Curie, Paris, France
| | | | - Valérie Briolat
- Institut Pasteur, Macrophages et Développement de l'Immunité, Department of Developmental and Stem Cells Biology, Paris, France
- CNRS URA2578, Paris, France
| | - Georges Lutfalla
- CNRS UMR5235, Dynamiques des Interactions Membranaires et Pathologiques, Montpellier, France
- Université Montpellier II, Montpellier, France
| | - Marion Sourisseau
- Institut Pasteur, Virus et Immunité, Department of Virology, Paris, France
- CNRS URA3015, Paris, France
| | - Felix Ellett
- Australian Regenerative Medicine Institute, Monash University, Clayton, Victoria, Australia
| | - Chieh-Huei Wang
- Australian Regenerative Medicine Institute, Monash University, Clayton, Victoria, Australia
| | - Graham J. Lieschke
- Australian Regenerative Medicine Institute, Monash University, Clayton, Victoria, Australia
| | - Philippe Herbomel
- Institut Pasteur, Macrophages et Développement de l'Immunité, Department of Developmental and Stem Cells Biology, Paris, France
- CNRS URA2578, Paris, France
| | - Olivier Schwartz
- Institut Pasteur, Virus et Immunité, Department of Virology, Paris, France
- CNRS URA3015, Paris, France
| | - Jean-Pierre Levraud
- Institut Pasteur, Macrophages et Développement de l'Immunité, Department of Developmental and Stem Cells Biology, Paris, France
- CNRS URA2578, Paris, France
- * E-mail:
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231
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Leung C, Chijioke O, Gujer C, Chatterjee B, Antsiferova O, Landtwing V, McHugh D, Raykova A, Münz C. Infectious diseases in humanized mice. Eur J Immunol 2013; 43:2246-54. [PMID: 23913412 DOI: 10.1002/eji.201343815] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2013] [Revised: 07/23/2013] [Accepted: 07/31/2013] [Indexed: 12/15/2022]
Abstract
Despite many theoretical incompatibilities between mouse and human cells, mice with reconstituted human immune system components contain nearly all human leukocyte populations. Accordingly, several human-tropic pathogens have been investigated in these in vivo models of the human immune system, including viruses such as human immunodeficiency virus (HIV) and Epstein-Barr virus (EBV), as well as bacteria such as Mycobacterium tuberculosis and Salmonella enterica Typhi. While these studies initially aimed to establish similarities in the pathogenesis of infections between these models and the pathobiology in patients, recent investigations have provided new and interesting functional insights into the protective value of certain immune compartments and altered pathology upon mutant pathogen infections. As more tools and methodologies are developed to make these models more versatile to study human immune responses in vivo, such improvements build toward small animal models with human immune components, which could predict immune responses to therapies and vaccination in human patients.
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Affiliation(s)
- Carol Leung
- Department of Viral Immunobiology, Institute of Experimental Immunology, University of Zurich, Zurich, Switzerland
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232
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Russell RA, Martin N, Mitar I, Jones E, Sattentau QJ. Multiple proviral integration events after virological synapse-mediated HIV-1 spread. Virology 2013; 443:143-9. [DOI: 10.1016/j.virol.2013.05.005] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2013] [Revised: 03/21/2013] [Accepted: 05/03/2013] [Indexed: 11/25/2022]
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233
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Malbec M, Sourisseau M, Guivel-Benhassine F, Porrot F, Blanchet F, Schwartz O, Casartelli N. HIV-1 Nef promotes the localization of Gag to the cell membrane and facilitates viral cell-to-cell transfer. Retrovirology 2013; 10:80. [PMID: 23899341 PMCID: PMC3734038 DOI: 10.1186/1742-4690-10-80] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2013] [Accepted: 07/26/2013] [Indexed: 11/16/2022] Open
Abstract
Background Newly synthesized HIV-1 particles assemble at the plasma membrane of infected cells, before being released as free virions or being transferred through direct cell-to-cell contacts to neighboring cells. Localization of HIV-1 Gag precursor at the cell membrane is necessary and sufficient to trigger viral assembly, whereas the GagPol precursor is additionally required to generate a fully matured virion. HIV-1 Nef is an accessory protein that optimizes viral replication through partly defined mechanisms. Whether Nef modulates Gag and/or GagPol localization and assembly at the membrane and facilitates viral cell-to-cell transfer has not been extensively characterized so far. Results We report that Nef increases the total amount of Gag proteins present in infected cells, and promotes Gag localization at the cell membrane. Moreover, the processing of p55 into p24 is improved in the presence of Nef. We also examined the effect of Nef during HIV-1 cell-to-cell transfer. We show that without Nef, viral transfer through direct contacts between infected cells and target cells is impaired. With a nef-deleted virus, the number of HIV-1 positive target cells after a short 2h co-culture is reduced, and viral material transferred to uninfected cells is less matured. At later time points, this defect is associated with a reduction in the productive infection of new target cells. Conclusions Our results highlight a previously unappreciated role of Nef during the viral replication cycle. Nef promotes HIV-1 Gag membrane localization and processing, and facilitates viral cell-to-cell transfer.
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Affiliation(s)
- Marine Malbec
- Département de Virologie, Institut Pasteur, Unité Virus et Immunité, 28 rue du Docteur Roux, Paris F-75015, France
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234
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Matrix metalloproteinases modulate ameboid-like migration of neutrophils through inflamed interstitial tissue. Blood 2013; 122:770-80. [PMID: 23757732 DOI: 10.1182/blood-2012-12-472944] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
In vitro studies suggest that leukocytes locomote in an ameboid fashion independently of pericellular proteolysis. Whether this motility pattern applies for leukocyte migration in inflamed tissue is still unknown. In vivo microscopy on the inflamed mouse cremaster muscle revealed that blockade of serine proteases or of matrix metalloproteinases (MMPs) significantly reduces intravascular accumulation and transmigration of neutrophils. Using a novel in vivo chemotaxis assay, perivenular microinjection of inflammatory mediators induced directional interstitial migration of neutrophils. Blockade of actin polymerization, but not of actomyosin contraction abolished neutrophil interstitial locomotion. Multiphoton laser scanning in vivo microscopy showed that the density of the interstitial collagen network increases in inflamed tissue, thereby providing physical guidance to infiltrating neutrophils. Although neutrophils locomote through the interstitium without pericellular collagen degradation, inhibition of MMPs, but not of serine proteases, diminished their polarization and interstitial locomotion. In this context, blockade of MMPs was found to modulate expression of adhesion/signaling molecules on neutrophils. Collectively, our data indicate that serine proteases are critical for neutrophil extravasation, whereas these enzymes are dispensable for neutrophil extravascular locomotion. By contrast, neutrophil interstitial migration strictly relies on actin polymerization and does not require the pericellular degradation of collagen fibers but is modulated by MMPs.
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235
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Brehm MA, Jouvet N, Greiner DL, Shultz LD. Humanized mice for the study of infectious diseases. Curr Opin Immunol 2013; 25:428-35. [PMID: 23751490 DOI: 10.1016/j.coi.2013.05.012] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2013] [Revised: 05/15/2013] [Accepted: 05/17/2013] [Indexed: 12/17/2022]
Abstract
Many of the pathogens that cause human infectious diseases do not infect rodents or other mammalian species. Small animal models that allow studies of the pathogenesis of these agents and evaluation of drug efficacy are critical for identifying ways to prevent and treat human infectious diseases. Immunodeficient mice engrafted with functional human cells and tissues, termed 'humanized' mice, represent a critical pre-clinical bridge for in vivo studies of human pathogens. Recent advances in the development of humanized mice have allowed in vivo studies of multiple human infectious agents providing novel insights into their pathogenesis that was otherwise not possible.
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Affiliation(s)
- Michael A Brehm
- Program in Molecular Medicine, University of Massachusetts Medical School, Worcester, MA 01655, United States
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236
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Sewald X, Gonzalez DG, Haberman AM, Mothes W. In vivo imaging of virological synapses. Nat Commun 2013; 3:1320. [PMID: 23271654 DOI: 10.1038/ncomms2338] [Citation(s) in RCA: 59] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2012] [Accepted: 11/23/2012] [Indexed: 11/09/2022] Open
Abstract
Retroviruses such as the human immunodeficiency virus, human T-cell lymphotropic virus and murine leukaemia virus are believed to spread via sites of cell-cell contact designated virological synapses. Support for this model is based on in vitro evidence in which infected cells are observed to specifically establish long-lived cell-cell contact with uninfected cells. Whether virological synapses exist in vivo is unknown. Here we apply intravital microscopy to identify a subpopulation of B cells infected with the Friend murine leukaemia virus that form virological synapses with uninfected leucocytes in the lymph node of living mice. In vivo virological synapses are, like their in vitro counterpart, dependent on the expression of the viral envelope glycoprotein and are characterized by a prolonged polarization of viral capsid to the cell-cell interface. Our results validate the concept of virological synapses and introduce intravital imaging as a tool to visualize retroviral spreading directly in living mice.
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Affiliation(s)
- Xaver Sewald
- Department of Microbial Pathogenesis, Yale University School of Medicine, New Haven, Connecticut 06510, USA
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237
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Thirty years on: HIV receptor gymnastics and the prevention of infection. BMC Biol 2013; 11:57. [PMID: 23692808 PMCID: PMC3660199 DOI: 10.1186/1741-7007-11-57] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2013] [Accepted: 05/10/2013] [Indexed: 11/10/2022] Open
Abstract
During 30 years of research on human immunodeficiency virus (HIV), our knowledge of its cellular receptors - CD4, CCR5 and CXCR4 - has illuminated aspects of the pathogenesis of the acquired immune deficiency syndrome (AIDS). Studying how the HIV envelope glycoproteins interact with the receptors led to anti-retroviral drugs based on blocking the docking or fusion of virus to the host cell. Genetic polymorphisms of CCR5 determine resistance to HIV infection and the rate of progression to AIDS. Eliciting neutralizing antibodies to the sites of receptor interaction on HIV glycoproteins is a promising approach to HIV vaccine development.
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238
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Koulakov AA, Lazebnik Y. The problem of colliding networks and its relation to cell fusion and cancer. Biophys J 2013. [PMID: 23199929 DOI: 10.1016/j.bpj.2012.08.062] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
Cell fusion, a process that merges two or more cells into one, is required for normal development and has been explored as a tool for stem cell therapy. It has also been proposed that cell fusion causes cancer and contributes to its progression. These functions rely on a poorly understood ability of cell fusion to create new cell types. We suggest that this ability can be understood by considering cells as attractor networks whose basic property is to adopt a set of distinct, stable, self-maintaining states called attractors. According to this view, fusion of two cell types is a collision of two networks that have adopted distinct attractors. To learn how these networks reach a consensus, we model cell fusion computationally. To do so, we simulate patterns of gene activities using a formalism developed to simulate patterns of memory in neural networks. We find that the hybrid networks can assume attractors that are unrelated to parental attractors, implying that cell fusion can create new cell types by nearly instantaneously moving cells between attractors. We also show that hybrid networks are prone to assume spurious attractors, which are emergent and sporadic network states. This finding means that cell fusion can produce abnormal cell types, including cancerous types, by placing cells into normally inaccessible spurious states. Finally, we suggest that the problem of colliding networks has general significance in many processes represented by attractor networks, including biological, social, and political phenomena.
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239
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Productive entry of HIV-1 during cell-to-cell transmission via dynamin-dependent endocytosis. J Virol 2013; 87:8110-23. [PMID: 23678185 DOI: 10.1128/jvi.00815-13] [Citation(s) in RCA: 50] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
HIV-1 can be transmitted as cell-free virus or via cell-to-cell contacts. Cell-to-cell transmission between CD4(+) T cells is the more efficient mode of transmission and is predominant in lymphoid tissue, where the majority of virus resides. Yet the cellular mechanisms underlying productive cell-to-cell transmission in uninfected target cells are unclear. Although it has been demonstrated that target cells can take up virus via endocytosis, definitive links between this process and productive infection remain undefined, and this route of transmission has been proposed to be nonproductive. Here, we report that productive cell-to-cell transmission can occur via endocytosis in a dynamin-dependent manner and is sensitive to clathrin-associated antagonists. These data were obtained in a number of CD4(+) T-cell lines and in primary CD4(+) T cells, using both CXCR4- and CCR5-tropic virus. However, we also found that HIV-1 demonstrated flexibility in its use of such endocytic pathways as certain allogeneic transmissions were seen to occur in a dynamin-dependent manner but were insensitive to clathrin-associated antagonists. Also, depleting cells of the clathrin accessory protein AP180 led to a viral uptake defect associated with enhanced infection. Collectively, these data demonstrate that endosomal uptake of HIV-1 during cell-to-cell transmission leads to productive infection, but they are also indicative of a flexible model of viral entry during cell-to-cell transmission, in which the virus can alter its entry route according to the pressures that it encounters.
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240
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Rinaldo CR. HIV-1 Trans Infection of CD4(+) T Cells by Professional Antigen Presenting Cells. SCIENTIFICA 2013; 2013:164203. [PMID: 24278768 PMCID: PMC3820354 DOI: 10.1155/2013/164203] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 02/28/2013] [Accepted: 04/09/2013] [Indexed: 06/02/2023]
Abstract
Since the 1990s we have known of the fascinating ability of a complex set of professional antigen presenting cells (APCs; dendritic cells, monocytes/macrophages, and B lymphocytes) to mediate HIV-1 trans infection of CD4(+) T cells. This results in a burst of virus replication in the T cells that is much greater than that resulting from direct, cis infection of either APC or T cells, or trans infection between T cells. Such APC-to-T cell trans infection first involves a complex set of virus subtype, attachment, entry, and replication patterns that have many similarities among APC, as well as distinct differences related to virus receptors, intracellular trafficking, and productive and nonproductive replication pathways. The end result is that HIV-1 can sequester within the APC for several days and be transmitted via membrane extensions intracellularly and extracellularly to T cells across the virologic synapse. Virus replication requires activated T cells that can develop concurrently with the events of virus transmission. Further research is essential to fill the many gaps in our understanding of these trans infection processes and their role in natural HIV-1 infection.
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Affiliation(s)
- Charles R. Rinaldo
- Department of Infectious Diseases and Microbiology, University of Pittsburgh Graduate School of Public Health, Pittsburgh, PA 15261, USA
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241
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Clustering and mobility of HIV-1 Env at viral assembly sites predict its propensity to induce cell-cell fusion. J Virol 2013; 87:7516-25. [PMID: 23637402 DOI: 10.1128/jvi.00790-13] [Citation(s) in RCA: 71] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
HIV-1 Env mediates virus attachment to and fusion with target cell membranes, and yet, while Env is still situated at the plasma membrane of the producer cell and before its incorporation into newly formed particles, Env already interacts with the viral receptor CD4 on target cells, thus enabling the formation of transient cell contacts that facilitate the transmission of viral particles. During this first encounter with the receptor, Env must not induce membrane fusion, as this would prevent the producer cell and the target cell from separating upon virus transmission, but how Env's fusion activity is controlled remains unclear. To gain a better understanding of the Env regulation that precedes viral transmission, we examined the nanoscale organization of Env at the surface of producer cells. Utilizing superresolution microscopy (stochastic optical reconstruction microscopy [STORM]) and fluorescence recovery after photobleaching (FRAP), we quantitatively assessed the clustering and dynamics of Env upon its arrival at the plasma membrane. We found that Gag assembly induced the aggregation of small Env clusters into larger domains and that these domains were completely immobile. Truncation of the cytoplasmic tail (CT) of Env abrogated Gag's ability to induce Env clustering and restored Env mobility at assembly sites, both of which correlated with increased Env-induced fusion of infected and uninfected cells. Hence, while Env trapping by Gag secures Env incorporation into viral particles, Env clustering and its sequestration at assembly sites likely also leads to the repression of its fusion function, and thus, by preventing the formation of syncytia, Gag helps to secure efficient transfer of viral particles to target cells.
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242
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Greenberg ML, Yu Y, Leverrier S, Zhang SL, Parker I, Cahalan MD. Orai1 function is essential for T cell homing to lymph nodes. JOURNAL OF IMMUNOLOGY (BALTIMORE, MD. : 1950) 2013; 190:3197-206. [PMID: 23455504 PMCID: PMC3608704 DOI: 10.4049/jimmunol.1202212] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
In T lymphocytes, Ca(2+) release-activated Ca(2+) (CRAC) channels composed of Orai1 subunits trigger Ag-induced gene expression and cell proliferation through the NFAT pathway. We evaluated the requirement of CRAC channel function for lymphocyte homing using expression of a dominant-negative Orai1-E106A mutant to suppress Ca(2+) signaling. To investigate homing and motility of human lymphocytes in immunocompromised mouse hosts, we transferred human lymphocytes either acutely or after stable engraftment after a second transfer from the same blood donor. Human and mouse lymphocyte homing was assessed, and cells were tracked within lymph nodes (LNs) by two-photon microscopy. Our results demonstrate that human T and B lymphocytes home into and migrate within the LNs of immunocompromised NOD.SCID mice similar to murine lymphocytes. Human T and B cells colocalized in atrophied or reconstituted mouse LNs, where T cells migrated in a random walk at velocities of 9-13 μm/min and B cells at 6 μm/min. Expression of Orai1-E106A inhibited CRAC channel function in human and mouse T cells, and prevented homing from high endothelial venules into murine LNs. Ca(2+) signals induced by CCL21 were also inhibited in T cells expressing Orai1-E106A. With CRAC channels inhibited, the high-affinity form of LFA-1 failed to become active, and T cells failed to migrate across endothelial cells in a transwell model. These results establish a requirement for CRAC channel-mediated Ca(2+) influx for T cell homing to LNs mediated by high-affinity integrin activation and chemokine-induced transendothelial migration.
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Affiliation(s)
- Milton L. Greenberg
- Department of Physiology and Biophysics, University of California, Irvine, CA
- Institute for Immunology, University of California, Irvine, CA
| | - Ying Yu
- Department of Physiology and Biophysics, University of California, Irvine, CA
- Institute for Immunology, University of California, Irvine, CA
| | - Sabrina Leverrier
- Department of Physiology and Biophysics, University of California, Irvine, CA
- Institute for Immunology, University of California, Irvine, CA
| | - Shenyuan L. Zhang
- Department of Physiology and Biophysics, University of California, Irvine, CA
- Institute for Immunology, University of California, Irvine, CA
| | - Ian Parker
- Department of Physiology and Biophysics, University of California, Irvine, CA
- Department of Neurobiology and Behavior, University of California, Irvine, CA
| | - Michael D. Cahalan
- Department of Physiology and Biophysics, University of California, Irvine, CA
- Institute for Immunology, University of California, Irvine, CA
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243
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HIV-1 Gag associates with specific uropod-directed microdomains in a manner dependent on its MA highly basic region. J Virol 2013; 87:6441-54. [PMID: 23536680 DOI: 10.1128/jvi.00040-13] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
In polarized T cells, HIV-1 Gag localizes to a rear-end protrusion known as the uropod in a multimerization-dependent manner. Gag-laden uropods participate in formation of virological synapses, intercellular contact structures that play a key role in cell-to-cell HIV-1 transmission. Our previous observations suggest that Gag associates with uropod-directed microdomains (UDMs) that eventually comigrate with Gag to the uropod over the cell surface. However, the nature of Gag multimerization required for this movement, the composition of the UDMs, and the molecular determinants for Gag association with these microdomains remain unknown. In this study, we found that Gag multimerization prior to budding but beyond dimerization is necessary for Gag localization to the uropods, indicating that uropod localization occurs early in the assembly process. We also found that prior to membrane curvature, Gag multimers associate with a specific subset of UDMs containing PSGL-1, CD43, and CD44 but not ICAM-1, ICAM-3, or CD59. Notably, upon association, Gag excludes ICAM-3 from this subset of UDMs, revealing an active and selective reorganization of these microdomains by Gag. This specific association between Gag and UDMs is dependent on the highly basic region (HBR) in the Gag matrix (MA) domain. The overall positive charge of the HBR was needed for the interaction with the specific UDM subset, while the exact HBR sequence was not, unlike that seen for MA binding to the plasma membrane phospholipid phosphatidylinositol-(4,5)-bisphosphate [PI(4,5)P2]. Taken together, these findings revealed that HIV-1 Gag associates with specific microdomains present in polarized T cells in an MA-dependent manner, which results in modification of the microdomain constituents.
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244
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Larsson M, Shankar EM, Che KF, Saeidi A, Ellegård R, Barathan M, Velu V, Kamarulzaman A. Molecular signatures of T-cell inhibition in HIV-1 infection. Retrovirology 2013; 10:31. [PMID: 23514593 PMCID: PMC3610157 DOI: 10.1186/1742-4690-10-31] [Citation(s) in RCA: 90] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2013] [Accepted: 03/07/2013] [Indexed: 01/07/2023] Open
Abstract
Cellular immune responses play a crucial role in the control of viral replication in HIV-infected individuals. However, the virus succeeds in exploiting the immune system to its advantage and therefore, the host ultimately fails to control the virus leading to development of terminal AIDS. The virus adopts numerous evasion mechanisms to hijack the host immune system. We and others recently described the expression of inhibitory molecules on T cells as a contributing factor for suboptimal T-cell responses in HIV infection both in vitro and in vivo. The expression of these molecules that negatively impacts the normal functions of the host immune armory and the underlying signaling pathways associated with their enhanced expression need to be discussed. Targets to restrain the expression of these molecular markers of immune inhibition is likely to contribute to development of therapeutic interventions that augment the functionality of host immune cells leading to improved immune control of HIV infection. In this review, we focus on the functions of inhibitory molecules that are expressed or secreted following HIV infection such as BTLA, CTLA-4, CD160, IDO, KLRG1, LAG-3, LILRB1, PD-1, TRAIL, TIM-3, and regulatory cytokines, and highlight their significance in immune inhibition. We also highlight the ensemble of transcriptional factors such as BATF, BLIMP-1/PRDM1, FoxP3, DTX1 and molecular pathways that facilitate the recruitment and differentiation of suppressor T cells in response to HIV infection.
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Affiliation(s)
- Marie Larsson
- Molecular Virology, Department of Clinical and Experimental Medicine, Linköping University, Linköping, 58 185, Sweden.
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245
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Chateau ML, Denton PW, Swanson MD, McGowan I, Garcia JV. Rectal transmission of transmitted/founder HIV-1 is efficiently prevented by topical 1% tenofovir in BLT humanized mice. PLoS One 2013; 8:e60024. [PMID: 23527295 PMCID: PMC3603991 DOI: 10.1371/journal.pone.0060024] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2012] [Accepted: 02/23/2013] [Indexed: 12/21/2022] Open
Abstract
Rectal microbicides are being developed to prevent new HIV infections in both men and women. We focused our in vivo preclinical efficacy study on rectally-applied tenofovir. BLT humanized mice (n = 43) were rectally inoculated with either the primary isolate HIV-1JRCSF or the MSM-derived transmitted/founder (T/F) virus HIV-1THRO within 30 minutes following treatment with topical 1% tenofovir or vehicle. Under our experimental conditions, in the absence of drug treatment we observed 50% and 60% rectal transmission by HIV-1JRCSF and HIV-1THRO, respectively. Topical tenofovir reduced rectal transmission to 8% (1/12; log rank p = 0.03) for HIV-1JRCSF and 0% (0/6; log rank p = 0.02) for HIV-1THRO. This is the first demonstration that any human T/F HIV-1 rectally infects humanized mice and that transmission of the T/F virus can be efficiently blocked by rectally applied 1% tenofovir. These results obtained in BLT mice, along with recent ex vivo, Phase 1 trial and non-human primate reports, provide a critically important step forward in the development of tenofovir-based rectal microbicides.
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Affiliation(s)
- Morgan L. Chateau
- Division of Infectious Diseases, Department of Internal Medicine, Center for AIDS Research University of North Carolina, Chapel Hill, North Carolina, United States of America
| | - Paul W. Denton
- Division of Infectious Diseases, Department of Internal Medicine, Center for AIDS Research University of North Carolina, Chapel Hill, North Carolina, United States of America
| | - Michael D. Swanson
- Division of Infectious Diseases, Department of Internal Medicine, Center for AIDS Research University of North Carolina, Chapel Hill, North Carolina, United States of America
| | - Ian McGowan
- Magee-Womens Research Institute, University of Pittsburgh Medical School, Pittsburgh, Pennsylvania, United States of America
| | - J. Victor Garcia
- Division of Infectious Diseases, Department of Internal Medicine, Center for AIDS Research University of North Carolina, Chapel Hill, North Carolina, United States of America
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Akkina R. New generation humanized mice for virus research: comparative aspects and future prospects. Virology 2013; 435:14-28. [PMID: 23217612 DOI: 10.1016/j.virol.2012.10.007] [Citation(s) in RCA: 150] [Impact Index Per Article: 13.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2012] [Revised: 10/03/2012] [Accepted: 10/03/2012] [Indexed: 12/27/2022]
Abstract
Work with human specific viruses will greatly benefit from the use of an in vivo system that provides human target cells and tissues in a physiological setting. In this regard humanized mice (hu-Mice) have played an important role in our understanding of viral pathogenesis and testing of therapeutic strategies. Limitations with earlier versions of hu-Mice that lacked a functioning human immune system are currently being overcome. The new generation hu-Mouse models are capable of multilineage human hematopoiesis and generate T cells, B cells, macrophages and dendritic cells required for an adaptive human immune response. Now any human specific pathogen that can infect humanized mice can be studied in the context of ongoing infection and immune responses. Two leading humanized mouse models are currently employed: the hu-HSC model is created by transplantation of human hematopoietic stem cells (HSC), whereas the BLT mouse model is prepared by transplantation of human fetal liver, thymus and HSC. A number of human specific viruses such as HIV-1, dengue, EBV and HCV are being studied intensively in these systems. Both models permit infection by mucosal routes with viruses such as HIV-1 thus allowing transmission prevention studies. Cellular and humoral immune responses are seen in both the models. While there is efficient antigen specific IgM production, IgG responses are suboptimal due to inefficient immunoglobulin class switching. With the maturation of T cells occurring in the autologous human thymus, BLT mice permit human HLA restricted T cell responses in contrast to hu-HSC mice. However, the strength of the immune responses needs further improvement in both models to reach the levels seen in humans. The scope of hu-Mice use is further broadened by transplantation of additional tissues like human liver thus permitting immunopathogenesis studies on hepatotropic viruses such as HCV. Numerous studies that encompass antivirals, gene therapy, viral evolution, and the generation of human monoclonal antibodies have been conducted with promising results in these mice. For further improvement of the new hu-Mouse models, ongoing work is focused on generating new strains of immunodeficient mice transgenic for human HLA molecules to strengthen immune responses and human cytokines and growth factors to improve human cell reconstitution and their homeostatic maintenance.
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Affiliation(s)
- Ramesh Akkina
- Department of Microbiology, Immunology and Pathology, Colorado State University, Fort Collins, CO 80523, USA.
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247
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Sigal A, Baltimore D. As good as it gets? The problem of HIV persistence despite antiretroviral drugs. Cell Host Microbe 2013; 12:132-8. [PMID: 22901535 DOI: 10.1016/j.chom.2012.07.005] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Human immunodeficienty virus (HIV) infection is suppressed but not eliminated by antiretroviral drugs. Viral persistence in the face of therapy has been explained by viral latency, lowered effectiveness of drugs in some anatomical sites and cell types, and cell-to-cell spread. These mechanisms allow for drug-sensitive virus to persist despite treatment. Understanding the persistence mechanism at work at different times after infection, including the time of initial infection immediately following transmission when reservoirs are first formed, will reveal if we are at the limit of what can be achieved with the current therapy paradigm of suppressing ongoing virus replication with drugs. We discuss some of the possible reasons why HIV persists at different points on the infection timeline, focusing on the role ongoing replication may have in maintaining the infection despite drugs at early times postexposure.
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Affiliation(s)
- Alex Sigal
- Division of Biology, California Institute of Technology, Pasadena, 91125, USA.
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Tsuiki A, Luo W, Henning T, Vishwanathan S, Dinh C, Adams D, Sweeney E, Mitchell J, Bachman S, Sharma P, Powell N, Hendry M, McNicholl J, Kersh E. Evaluation of the lymphocyte trafficking drug FTY720 in vaginal tissues. J Med Primatol 2013; 42:89-100. [PMID: 23311598 DOI: 10.1111/jmp.12033] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 12/10/2012] [Indexed: 11/27/2022]
Abstract
BACKGROUND FTY720 is an immunomodulatory agent that reduces lymphocytes in peripheral tissues and circulation. Such agents may be effective as vaginal microbicides for HIV prevention. Systemic or vaginal application of FTY720 may reduce lymphocyte concentrations in genital tissues, reducing HIV target cell numbers. METHODS Five female pigtail macaques received topical vaginal gel FTY720 (n = 2), intravenous (i.v.) FTY720 (n = 2), or placebo gel (n = 1) in this pilot study. Circulating and mucosal lymphocytes and genital mucosa, cytokines, and tissue histology were analyzed to document topical and i.v. FTY720 effects. RESULTS Topical and i.v. FTY720 appeared to decrease the levels of cervicovaginal IL-8, IL-1ra, and genital inflammatory cells. Small sample size precluded statistical analysis. Topical administration had no overt adverse effects. CONCLUSIONS This study introduces FTY720 as an immunomodulatory agent for the vaginal mucosa, compares topical effects to those of i.v. administration, and provides the basis for future studies involving FTY720 for HIV prevention.
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Affiliation(s)
- Ai Tsuiki
- Division of Scientific Resources, NCEZID, CDC, Atlanta, GA 30333, USA
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249
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Stürzel CM, Palesch D, Khalid M, Wissing S, Fischer N, Münch J. Utilization of replication-competent XMRV reporter-viruses reveals severe viral restriction in primary human cells. PLoS One 2013; 8:e74427. [PMID: 24058563 PMCID: PMC3772927 DOI: 10.1371/journal.pone.0074427] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2013] [Accepted: 08/01/2013] [Indexed: 11/20/2022] Open
Abstract
The gammaretrovirus termed xenotropic murine leukemia virus-related virus (XMRV) was described to be isolated from prostate cancer tissue biopsies and from blood of patients suffering from chronic fatigue syndrome. However, many studies failed to detect XMRV and to verify these disease associations. Data suggesting the contamination of specimens in particular by PCR-based methods and recent reports demonstrating XMRV generation via recombination of two murine leukemia virus precursors raised serious doubts about XMRV being a genuine human pathogen. To elucidate cell tropism of XMRV, we generated replication competent XMRV reporter viruses encoding a green fluorescent protein or a secretable luciferase as tools to analyze virus infection of human cell lines or primary human cells. Transfection of proviral DNAs into LNCaP prostate cancer cells resulted in readily detectably reporter gene expression and production of progeny virus. Inoculation of known XMRV susceptible target cells revealed that these virions were infectious and expressed the reporter gene, allowing for a fast and highly sensitive quantification of XMRV infection. Both reporter viruses were capable of establishing a spreading infection in LNCaP and Raji B cells and could be easily passaged. However, after inoculation of primary human blood cells such as CD4 T cells, macrophages or dendritic cells, infection rates were very low, and a spreading infection was never established. In line with these results we found that supernatants derived from these XMRV infected primary cell types did not contain infectious virus. Thus, although XMRV efficiently replicated in some human cell lines, all tested primary cells were largely refractory to XMRV infection and did not support viral spread. Our results provide further evidence that XMRV is not a human pathogen.
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Affiliation(s)
| | - David Palesch
- Institute of Molecular Virology, Ulm University Medical Centre, Ulm, Germany
| | - Mohammad Khalid
- Institute of Molecular Virology, Ulm University Medical Centre, Ulm, Germany
| | - Silke Wissing
- Gladstone Institute of Virology and Immunology, University of California San Francisco, San Francisco, California, United States of America
| | - Nicole Fischer
- Institute for Medical Microbiology, Virology and Hygiene, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
| | - Jan Münch
- Institute of Molecular Virology, Ulm University Medical Centre, Ulm, Germany
- * E-mail:
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250
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Zhong P, Agosto LM, Munro JB, Mothes W. Cell-to-cell transmission of viruses. Curr Opin Virol 2012; 3:44-50. [PMID: 23219376 DOI: 10.1016/j.coviro.2012.11.004] [Citation(s) in RCA: 154] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2012] [Revised: 10/28/2012] [Accepted: 11/13/2012] [Indexed: 01/08/2023]
Abstract
The life cycle of most viruses involves the release of particles into the extracellular space. Consequently, the study of virus egress as well as virus entry has focused almost exclusively on the biology of cell-free virus. However, cell-free virus spread is often very inefficient. Specific barriers, either located in the donor cell or in the target cell, prevent efficient spread by the cell-free mode. In contrast, viral spread by direct cell-cell contact is largely unaffected by most of these barriers resulting in preferential spread by cell-to-cell transmission. Virus cell-to-cell transmission allows an efficient coordination of several steps of the viral life cycle. It often involves complex inter-cellular adhesion, cellular polarity and intra-cellular trafficking. Because virus cell-to-cell transmission can involve transmission through zones of tight cell-cell contact that are resistant to neutralizing antibodies and reach a high local particle concentration, cell-to-cell transmission can contribute to the pathogenesis of viral infections.
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Affiliation(s)
- Peng Zhong
- Department of Microbial Pathogenesis, Yale University School of Medicine, 295 Congress Ave., New Haven, CT 06536, USA
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