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Robert W. Doms - One of the best experts on this subject based on the ideXlab platform.
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HIV: Cell Binding and Entry
Cold Spring Harbor perspectives in medicine, 2012Co-Authors: Craig B. Wilen, John C. Tilton, Robert W. DomsAbstract:The first step of the human immunodeficiency virus (HIV) replication cycle-binding and entry into the host cell-plays a major role in determining Viral Tropism and the ability of HIV to degrade the human immune system. HIV uses a complex series of steps to deliver its genome into the host cell cytoplasm while simultaneously evading the host immune response. To infect cells, the HIV protein envelope (Env) binds to the primary cellular receptor CD4 and then to a cellular coreceptor. This sequential binding triggers fusion of the Viral and host cell membranes, initiating infection. Revealing the mechanism of HIV entry has profound implications for Viral Tropism, transmission, pathogenesis, and therapeutic intervention. Here, we provide an overview into the mechanism of HIV entry, provide historical context to key discoveries, discuss recent advances, and speculate on future directions in the field.
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Efficient production of Hantaan and Puumala pseudovirions for Viral Tropism and neutralization studies.
Virology, 2011Co-Authors: Meda M. Higa, Josiah Petersen, Jay W. Hooper, Robert W. DomsAbstract:Abstract Puumala (PUUV) and Hantaan (HTNV) viruses are hantaviruses within the family Bunyaviridae and associated with Hemorrhagic Fever with Renal Syndrome (HFRS) in humans. Little is known about how these viruses interact with host cells, though pathogenic hantaviruses interact with α v β 3 integrin. To study host cell interactions and rapidly test the ability of antibodies to prevent infection, we produced HTNV and PUUV pseudovirions on a vesicular stomatitis virus (VSV) core. Similar to replication-competent hantaviruses, infection was low-pH-dependent. Despite broad cell Tropism, several human T cell lines were poorly permissive to hantavirus pseudovirions, compared to VSV, indicating a relative block to infection at the level of entry. Stable expression of α v β 3 integrin in SupT1 cells did not restore infectivity. Finally, the pseudovirion system provided a rapid, quantitative, and specific method to screen for neutralizing antibodies in immune sera.
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a biosensor assay for studying ligand membrane receptor interactions binding of antibodies and hiv 1 env to chemokine receptors
Proceedings of the National Academy of Sciences of the United States of America, 2000Co-Authors: Trevor L Hoffman, Gabriela Canziani, Li Jia, Joseph Rucker, Robert W. DomsAbstract:The HIV envelope (Env) protein mediates entry into cells by binding CD4 and an appropriate coreceptor, which triggers structural changes in Env that lead to fusion between the Viral and cellular membranes. The major HIV-1 coreceptors are the seven transmembrane domain chemokine receptors CCR5 and CXCR4. The type of coreceptor used by a virus strain is an important determinant of Viral Tropism and pathogenesis, and virus-receptor interactions can be therapeutic targets. However, Envs from many virus strains interact with CXCR4 and CCR5 with low affinity such that direct study of this important interaction is difficult if not impossible using standard cell-surface binding techniques. We have developed an approach that makes it possible to study ligand binding to membrane proteins, including Env-coreceptor interactions, using an optical biosensor. CCR5, CXCR4, and other membrane proteins were incorporated into retrovirus particles, which were purified and attached to the biosensor surface. Binding of conformationally sensitive antibodies as well as Env to these receptors was readily detected. The equilibrium dissociation constant for the interaction between an Env derived from the prototype HIV-1 strain IIIB for CXCR4 was approximately 500 nM, explaining the difficulty in measuring this interaction using standard equilibrium binding techniques. RetroViral pseudotypes represent easily produced, stable, homogenous structures that can be used to present a wide array of single and multiple membrane-spanning proteins in a native lipid environment for biosensor studies, thus avoiding the need for detergent solubilization, purification, and reconstitution. The approach should have general applicability and can be used to correlate Env-receptor binding constants to Viral Tropism and pathogenesis.
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HIV-1 Coreceptors and Viral Tropism
Chemokines in Disease, 1999Co-Authors: Robert W. Doms, John P. MooreAbstract:The past two years have witnessed the rapid merging of the HIV and chemokine-receptor fields, no doubt to the surprise of all involved (reviewed in refs. 1–4). It became evident soon after the discovery of CD4 as the primary receptor for HIV-1 that one or more additional cell-surface molecules (coreceptors) were required in conjunction with CD4 to support entry of the virus into cells (5). The realization that HIV-1 strains exhibit distinct cellular Tropisms indicated that strain-specific coreceptors might exist. Over the ensuing decade, numerous candidate coreceptors were proposed, none of which stood the test of time. Finally, the first significant step towards solving this problem came in late 1995 when Cocchi, Lusso, and co-workers identified the CC chemokines RANTES, MIP-1α, and MIP-1β as factors secreted by CD8+ T cells that were able to suppress some HIV-1 strains (6). However, the true significance of this finding was not fully apparent until Berger and colleagues independently identified the first bona fide HIV-1 coreceptor, termed fusin (7). This was an orphan seven transmembrane domain receptor first cloned in 1993 (8). Of significance for understanding HIV-1 Tropism was that, whereas fusin was clearly shown to serve as a coreceptor for T-tropic virus strains, expression of fusin with CD4 did not allow entry of the more common M-tropic viruses (7). However, the homology of fusin to the chemokine receptor family indicated that a receptor competent to bind RANTES, MIP1-α, and MIP1-β would be an excellent candidate for the M-tropic virus coreceptor. The publication of a receptor with this binding profile, termed CCR5 (9) enabled five groups to simultaneously identify this molecule as the major HIV-1 coreceptor (10–14). Confirmation that CCR5 is the major HIV-1 coreceptor in vivo came from the finding that individuals who lack CCR5 because of an inherited polymorphism (D32-ccr5) are highly resistant to virus infection, and that individuals who have only one copy of this allele exhibit a delayed progression to AIDS (15–17). Subsequently, fusin was shown to be the receptor for the CXC chemokine SDF-1 and, as a result, was renamed CXCR4 (18,19).
Mayte Perez-olmeda - One of the best experts on this subject based on the ideXlab platform.
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Deep-Sequencing Analysis of the Dynamics of HIV-1 Quasiespecies in Naive Patients during a Short Exposure to Maraviroc.
Journal of virology, 2018Co-Authors: Almudena Cascajero, Beatriz Hernández-novoa, José Alcamí, Santiago Moreno, Alberto Rastrojo, Francisco Díez-fuertes, Begoña Aguado, Mayte Perez-olmedaAbstract:In this study, we have characterized quasispecies dynamics and the evolution of Viral Tropism in naive HIV-1-infected patients treated with a short course of maraviroc monotherapy (ClinicalTrials.gov registration no. NCT01060618) independently of the Tropism of the infecting virus. We randomly selected 20 patients infected with viruses displaying different basal Tropisms-10 carrying R5 and 10 carrying dual/mixed X4 (DM/X4) viruses-at recruitment as determined by phenotypic assay (Trofile). Evolution of Viral quasiespecies at the end of treatment was determined by ultradeep sequencing of the V3 region using a 454 Life Sciences Platform and geno2pheno (g2p) algorithm for Viral Tropism prediction. The false-positive rate (FPR) that defines the probability of classifying an R5 virus falsely as X4 was set at 10%. X4-specific HIV-1 Viral load (VL) was calculated from sequences with an FPR of 1-log10 copies/ml reduction in VL was detected in 70% of patients independently of the basal Tropism of the infecting virus. Viral Tropism remained stable, and nonsignificant differences in FPR values before and after treatment were found for the majority of patients in both Tropism groups. Only three patients (one with R5 and two with DM/X4 viruses) showed an increased (>1 log) X4 VL, and one patient harboring a DM/X4-tropic virus displayed a significant reduction in FPR values at the end of treatment. Fast changes in the composition of Viral populations were observed in all patients after 10 days of maraviroc (MVC) monotherapy treatment, and a complete replacement of Viral quasiespecies was found in 3/10 patients carrying R5-using viruses and 4/10 patients carrying DM/X4-using viruses.IMPORTANCE Initiation of treatment with maraviroc requires previous determination of Viral Tropism by genotypic or phenotypic methods because of the risk of treatment failure and selection of DM/X4-tropic variants. In this study, we confirm previous work showing that the virologic response to maraviroc is independent of basal Tropism. By deep-sequencing analysis, we determined that fast changes in Viral populations were due to the emergence of minority variants in some patients whereas in others generation of new strains was detected. The risk of DM/X4 selection was very low as FPR values remained stable, and only one patient showed a detrimental switch to DM/X4 variants. Our data show that some DM/X4 viruses are sensitive to maraviroc treatment probably because only a low proportion of DM/X4 viruses use preferentially the X4 receptor and contain authentically maraviroc-resistant viruses that are not accurately detected by current assays.
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Determination of HIV Tropism and its use in the clinical practice
Expert review of anti-infective therapy, 2013Co-Authors: Mayte Perez-olmeda, José AlcamíAbstract:Assessment of HIV coreceptor Tropism assay is recommended before starting therapy with CCR5 coreceptor antagonists. So far, only maraviroc (MVC) has been approved for clinical use and a Tropism assay is mandatory for patients with virological failure or patients in which MVC is considered into future treatment options. Viral Tropism can be assessed with either genotypic or phenotypic methods and to this aim different techniques have been developed. However, it is unclear which assay is more appropriate for routine testing. In fact, although phenotypic assays are considered the gold standard as they directly measure the Viral Tropism and current versions allow detection of a lower threshold of minor CXCR4-dependent variants, the genotypic assays present major practical advantages for their use in the clinical setting.
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Methods for determining Viral Tropism: genotype and phenotype tests
Enfermedades infecciosas y microbiologia clinica, 2008Co-Authors: Mayte Perez-olmeda, Eva PovedaAbstract:The recent approval of the first CCR5 antagonist, Maraviroc (MVC, Celsentri), with specific antiViral activity against R5-tropic virus variants has generated the need for studies to determine the Viral Tropism in all those patient candidates for starting treatment with this new drug. Although genotyping methods appear to be the most useful tool due to its speed and simplicity, in the case of Viral Tropism, phenotyping techniques are currently considered the most reliable. In the last few years, different phenotyping assays have been developed to determine the use of the co-receptor. However, the Trofile phenotype assay is currently the one most used for the determination of Tropism, since it is the only one that has been clinically validated. Given that the presence of X4- tropic variants in the Viral population has been associated with virological failure to MVC, the main challenge of both genotyping and phenotyping tools is to optimise their sensitivity for detecting X4-tropic variants present in a minority of the Viral population. At the same time, the correlation between genotyping/phenotyping methods is being evaluated to determine whether genotyping tools can be useful to make therapeutic decisions.
Walter J. Atwood - One of the best experts on this subject based on the ideXlab platform.
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Derivation of a JC virus-resistant human glial cell line: implications for the identification of host cell factors that determine Viral Tropism.
Virology, 2003Co-Authors: Gretchen V. Gee, Kate Manley, Walter J. AtwoodAbstract:JC virus (JCV) is a common human polyomavirus that infects 70-80% of the population worldwide. In immunosuppressed individuals, JCV infects oligodendrocytes and causes a fatal demyelinating disease known as progressive multifocal leukoencephalopathy (PML). The Tropism of JCV is restricted to oligodendrocytes, astrocytes, and B lymphocytes. Several mechanisms may contribute to the restricted Tropism of JCV, including the presence or absence of cell-type-specific transcription and replication factors and the presence or absence of cell-type-specific receptors. We have established a system to investigate cellular factors that influence Viral Tropism by selecting JCV-resistant cells from a susceptible glial cell line (SVG-A). SVG-A cells were subjected to several rounds of Viral infection using JC virus (M1/SVE Delta). A population of resistant cells emerged (SVGR2) that were refractory to infection with the Mad-4 strain of JCV, the hybrid virus M1/SVE Delta, as well as to the related polyomavirus SV40. SVGR2 cells were as susceptible as the SVG-A cells to infection with an unrelated amphotropic retrovirus. The stage at which these cells are resistant to infection was investigated and the block appears to be at early Viral gene transcription. This system should ultimately allow us to identify glial specific factors that influence the Tropism of JCV.
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derivation of a jc virus resistant human glial cell line implications for the identification of host cell factors that determine Viral Tropism
Virology, 2003Co-Authors: Gretchen V. Gee, Kate Manley, Walter J. AtwoodAbstract:Abstract JC virus (JCV) is a common human polyomavirus that infects 70–80% of the population worldwide. In immunosuppressed individuals, JCV infects oligodendrocytes and causes a fatal demyelinating disease known as progressive multifocal leukoencephalopathy (PML). The Tropism of JCV is restricted to oligodendrocytes, astrocytes, and B lymphocytes. Several mechanisms may contribute to the restricted Tropism of JCV, including the presence or absence of cell-type-specific transcription and replication factors and the presence or absence of cell-type-specific receptors. We have established a system to investigate cellular factors that influence Viral Tropism by selecting JCV-resistant cells from a susceptible glial cell line (SVG-A). SVG-A cells were subjected to several rounds of Viral infection using JC virus (M1/SVEΔ). A population of resistant cells emerged (SVGR2) that were refractory to infection with the Mad-4 strain of JCV, the hybrid virus M1/SVEΔ, as well as to the related polyomavirus SV40. SVGR2 cells were as susceptible as the SVG-A cells to infection with an unrelated amphotropic retrovirus. The stage at which these cells are resistant to infection was investigated and the block appears to be at early Viral gene transcription. This system should ultimately allow us to identify glial specific factors that influence the Tropism of JCV.
Carlo Torti - One of the best experts on this subject based on the ideXlab platform.
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structural equation modelling of Viral Tropism reveals its impact on achieving Viral suppression within 6 months in treatment naive hiv 1 infected patients after combination antiretroViral therapy
Journal of Antimicrobial Chemotherapy, 2017Co-Authors: Carlo Mengoli, Samantha Andreis, Renzo Scaggiante, Mario Cruciani, Oliviero Bosco, Roberto Ferretto, Davide Leoni, Gaetano Maffongelli, Monica Basso, Carlo TortiAbstract:OBJECTIVES To evaluate the role of pre-treatment co-receptor Tropism of plasma HIV on the achievement of Viral suppression (plasma HIV RNA 1.69 log10 copies/mL) at the sixth month of combination antiretroViral therapy (cART) in a cohort of naive patients using, for the first time in this context, a path analysis (PA) approach. PATIENTS AND METHODS Adult patients with chronic infection by subtype B HIV-1 were consecutively enrolled from the start of first-line cART (T0). Genotypic analysis of Viral Tropism was performed on plasma and interpreted using the bioinformatic tool Geno2pheno, with a false positive rate of 10%. A Bayesian network starting from the viro-immunological data at T0 and at the sixth month of treatment (T1) was set up and this model was evaluated using a PA approach. RESULTS A total of 262 patients (22.1% bearing an X4 virus) were included; 178 subjects (67.9%) achieved Viral suppression. A significant positive indirect effect of bearing X4 virus in plasma at T0 on log10 HIV RNA at T1 was detected (P = 0.009), the magnitude of this effect was, however, over 10-fold lower than the direct effect of log10 HIV RNA at T0 on log10 HIV RNA at T1 (P = 0.000). Moreover, a significant positive indirect effect of bearing an X4 virus on log10 HIV RNA at T0 (P = 0.003) was apparent. CONCLUSIONS PA overcame the limitations implicit in common multiple regression analysis and showed the possible role of pre-treatment Viral Tropism at the recommended threshold on the outcome of plasma viraemia in naive patients after 6 months of therapy.
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Structural equation modelling of Viral Tropism reveals its impact on achieving Viral suppression within 6 months in treatment-naive HIV-1-infected patients after combination antiretroViral therapy
The Journal of antimicrobial chemotherapy, 2016Co-Authors: Carlo Mengoli, Samantha Andreis, Renzo Scaggiante, Mario Cruciani, Oliviero Bosco, Roberto Ferretto, Davide Leoni, Gaetano Maffongelli, Monica Basso, Carlo TortiAbstract:To evaluate the role of pre-treatment co-receptor Tropism of plasma HIV on the achievement of Viral suppression (plasma HIV RNA 1.69 log10 copies/mL) at the sixth month of combination antiretroViral therapy (cART) in a cohort of naive patients using, for the first time in this context, a path analysis (PA) approach. Adult patients with chronic infection by subtype B HIV-1 were consecutively enrolled from the start of first-line cART (T0). Genotypic analysis of Viral Tropism was performed on plasma and interpreted using the bioinformatic tool Geno2pheno, with a false positive rate of 10%. A Bayesian network starting from the viro-immunological data at T0 and at the sixth month of treatment (T1) was set up and this model was evaluated using a PA approach. A total of 262 patients (22.1% bearing an X4 virus) were included; 178 subjects (67.9%) achieved Viral suppression. A significant positive indirect effect of bearing X4 virus in plasma at T0 on log10 HIV RNA at T1 was detected (P = 0.009), the magnitude of this effect was, however, over 10-fold lower than the direct effect of log10 HIV RNA at T0 on log10 HIV RNA at T1 (P = 0.000). Moreover, a significant positive indirect effect of bearing an X4 virus on log10 HIV RNA at T0 (P = 0.003) was apparent. PA overcame the limitations implicit in common multiple regression analysis and showed the possible role of pre-treatment Viral Tropism at the recommended threshold on the outcome of plasma viraemia in naive patients after 6 months of therapy. © The Author 2016. Published by Oxford University Press on behalf of the British Society for Antimicrobial Chemotherapy. All rights reserved. For Permissions, please e-mail: journals.permissions@oup.com.
Gretchen V. Gee - One of the best experts on this subject based on the ideXlab platform.
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Derivation of a JC virus-resistant human glial cell line: implications for the identification of host cell factors that determine Viral Tropism.
Virology, 2003Co-Authors: Gretchen V. Gee, Kate Manley, Walter J. AtwoodAbstract:JC virus (JCV) is a common human polyomavirus that infects 70-80% of the population worldwide. In immunosuppressed individuals, JCV infects oligodendrocytes and causes a fatal demyelinating disease known as progressive multifocal leukoencephalopathy (PML). The Tropism of JCV is restricted to oligodendrocytes, astrocytes, and B lymphocytes. Several mechanisms may contribute to the restricted Tropism of JCV, including the presence or absence of cell-type-specific transcription and replication factors and the presence or absence of cell-type-specific receptors. We have established a system to investigate cellular factors that influence Viral Tropism by selecting JCV-resistant cells from a susceptible glial cell line (SVG-A). SVG-A cells were subjected to several rounds of Viral infection using JC virus (M1/SVE Delta). A population of resistant cells emerged (SVGR2) that were refractory to infection with the Mad-4 strain of JCV, the hybrid virus M1/SVE Delta, as well as to the related polyomavirus SV40. SVGR2 cells were as susceptible as the SVG-A cells to infection with an unrelated amphotropic retrovirus. The stage at which these cells are resistant to infection was investigated and the block appears to be at early Viral gene transcription. This system should ultimately allow us to identify glial specific factors that influence the Tropism of JCV.
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derivation of a jc virus resistant human glial cell line implications for the identification of host cell factors that determine Viral Tropism
Virology, 2003Co-Authors: Gretchen V. Gee, Kate Manley, Walter J. AtwoodAbstract:Abstract JC virus (JCV) is a common human polyomavirus that infects 70–80% of the population worldwide. In immunosuppressed individuals, JCV infects oligodendrocytes and causes a fatal demyelinating disease known as progressive multifocal leukoencephalopathy (PML). The Tropism of JCV is restricted to oligodendrocytes, astrocytes, and B lymphocytes. Several mechanisms may contribute to the restricted Tropism of JCV, including the presence or absence of cell-type-specific transcription and replication factors and the presence or absence of cell-type-specific receptors. We have established a system to investigate cellular factors that influence Viral Tropism by selecting JCV-resistant cells from a susceptible glial cell line (SVG-A). SVG-A cells were subjected to several rounds of Viral infection using JC virus (M1/SVEΔ). A population of resistant cells emerged (SVGR2) that were refractory to infection with the Mad-4 strain of JCV, the hybrid virus M1/SVEΔ, as well as to the related polyomavirus SV40. SVGR2 cells were as susceptible as the SVG-A cells to infection with an unrelated amphotropic retrovirus. The stage at which these cells are resistant to infection was investigated and the block appears to be at early Viral gene transcription. This system should ultimately allow us to identify glial specific factors that influence the Tropism of JCV.
