1
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Cassidy T, Stephenson KE, Barouch DH, Perelson AS. Modeling resistance to the broadly neutralizing antibody PGT121 in people living with HIV-1. PLoS Comput Biol 2024; 20:e1011518. [PMID: 38551976 PMCID: PMC11006161 DOI: 10.1371/journal.pcbi.1011518] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2023] [Revised: 04/10/2024] [Accepted: 03/14/2024] [Indexed: 04/11/2024] Open
Abstract
PGT121 is a broadly neutralizing antibody in clinical development for the treatment and prevention of HIV-1 infection via passive administration. PGT121 targets the HIV-1 V3-glycan and demonstrated potent antiviral activity in a phase I clinical trial. Resistance to PGT121 monotherapy rapidly occurred in the majority of participants in this trial with the sampled rebound viruses being entirely resistant to PGT121 mediated neutralization. However, two individuals experienced long-term ART-free viral suppression following antibody infusion and retained sensitivity to PGT121 upon viral rebound. Here, we develop mathematical models of the HIV-1 dynamics during this phase I clinical trial. We utilize these models to understand the dynamics leading to PGT121 resistance and to identify the mechanisms driving the observed long-term viral control. Our modeling highlights the importance of the relative fitness difference between PGT121 sensitive and resistant subpopulations prior to treatment. Specifically, by fitting our models to data, we identify the treatment-induced competitive advantage of previously existing or newly generated resistant population as a primary driver of resistance. Finally, our modeling emphasizes the high neutralization ability of PGT121 in both participants who exhibited long-term viral control.
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Affiliation(s)
- Tyler Cassidy
- School of Mathematics, University of Leeds, Leeds, United Kingdom
| | - Kathryn E. Stephenson
- Center for Virology and Vaccine Research, Beth Israel Deaconess Medical Center, Boston, Massachusetts, United States of America
- Division of Infectious Diseases, Beth Israel Deaconess Medical Center, Boston, Massachusetts, United States of America
- Ragon Institute of MGH, MIT and Harvard, Cambridge, Massachusetts, United States of America
| | - Dan H. Barouch
- Center for Virology and Vaccine Research, Beth Israel Deaconess Medical Center, Boston, Massachusetts, United States of America
- Division of Infectious Diseases, Beth Israel Deaconess Medical Center, Boston, Massachusetts, United States of America
- Ragon Institute of MGH, MIT and Harvard, Cambridge, Massachusetts, United States of America
| | - Alan S. Perelson
- Theoretical Biology and Biophysics, Los Alamos National Laboratory, Los Alamos, New Mexico, United States of America
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2
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Policicchio BB, Cardozo-Ojeda EF, Xu C, Ma D, He T, Raehtz KD, Sivanandham R, Kleinman AJ, Perelson AS, Apetrei C, Pandrea I, Ribeiro RM. CD8 + T cells control SIV infection using both cytolytic effects and non-cytolytic suppression of virus production. Nat Commun 2023; 14:6657. [PMID: 37863982 PMCID: PMC10589330 DOI: 10.1038/s41467-023-42435-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2022] [Accepted: 10/11/2023] [Indexed: 10/22/2023] Open
Abstract
Whether CD8+ T lymphocytes control human immunodeficiency virus infection by cytopathic or non-cytopathic mechanisms is not fully understood. Multiple studies highlighted non-cytopathic effects, but one hypothesis is that cytopathic effects of CD8+ T cells occur before viral production. Here, to examine the role of CD8+ T cells prior to virus production, we treated SIVmac251-infected macaques with an integrase inhibitor combined with a CD8-depleting antibody, or with either reagent alone. We analyzed the ensuing viral dynamics using a mathematical model that included infected cells pre- and post- viral DNA integration to compare different immune effector mechanisms. Macaques receiving the integrase inhibitor alone experienced greater viral load decays, reaching lower nadirs on treatment, than those treated also with the CD8-depleting antibody. Models including CD8+ cell-mediated reduction of viral production (non-cytolytic) were found to best explain the viral profiles across all macaques, in addition an effect in killing infected cells pre-integration (cytolytic) was supported in some of the best models. Our results suggest that CD8+ T cells have both a cytolytic effect on infected cells before viral integration, and a direct, non-cytolytic effect by suppressing viral production.
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Affiliation(s)
- Benjamin B Policicchio
- Department of Infectious Diseases and Microbiology, Graduate School of Public Health, University of Pittsburgh, Pittsburgh, PA, 15261, USA
| | | | - Cuiling Xu
- Department of Pathology, School of Medicine, University of Pittsburgh, Pittsburgh, PA, 15261, USA
| | - Dongzhu Ma
- Department of Pathology, School of Medicine, University of Pittsburgh, Pittsburgh, PA, 15261, USA
| | - Tianyu He
- Department of Pathology, School of Medicine, University of Pittsburgh, Pittsburgh, PA, 15261, USA
| | - Kevin D Raehtz
- Division of Infectious Diseases, Department of Medicine, School of Medicine, University of Pittsburgh, Pittsburgh, PA, 15261, USA
| | - Ranjit Sivanandham
- Department of Pathology, School of Medicine, University of Pittsburgh, Pittsburgh, PA, 15261, USA
| | - Adam J Kleinman
- Division of Infectious Diseases, Department of Medicine, School of Medicine, University of Pittsburgh, Pittsburgh, PA, 15261, USA
| | - Alan S Perelson
- Theoretical Biology and Biophysics Group, Los Alamos National Laboratory, Los Alamos, NM, 87545, USA
| | - Cristian Apetrei
- Department of Infectious Diseases and Microbiology, Graduate School of Public Health, University of Pittsburgh, Pittsburgh, PA, 15261, USA
- Division of Infectious Diseases, Department of Medicine, School of Medicine, University of Pittsburgh, Pittsburgh, PA, 15261, USA
| | - Ivona Pandrea
- Department of Infectious Diseases and Microbiology, Graduate School of Public Health, University of Pittsburgh, Pittsburgh, PA, 15261, USA
- Department of Pathology, School of Medicine, University of Pittsburgh, Pittsburgh, PA, 15261, USA
| | - Ruy M Ribeiro
- Theoretical Biology and Biophysics Group, Los Alamos National Laboratory, Los Alamos, NM, 87545, USA.
- Laboratório de Biomatemática, Faculdade de Medicina da Universidade de Lisboa (previous address), Lisboa, Portugal.
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3
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Swan DA, Rolland M, Herbeck JT, Schiffer JT, Reeves DB. Evolution during primary HIV infection does not require adaptive immune selection. Proc Natl Acad Sci U S A 2022; 119:e2109172119. [PMID: 35145025 DOI: 10.1073/pnas.2109172119] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 12/16/2021] [Indexed: 01/20/2023] Open
Abstract
Modern HIV research depends crucially on both viral sequencing and population measurements. To directly link mechanistic biological processes and evolutionary dynamics during HIV infection, we developed multiple within-host phylodynamic models of HIV primary infection for comparative validation against viral load and evolutionary dynamics data. The optimal model of primary infection required no positive selection, suggesting that the host adaptive immune system reduces viral load but surprisingly does not drive observed viral evolution. Rather, the fitness (infectivity) of mutant variants is drawn from an exponential distribution in which most variants are slightly less infectious than their parents (nearly neutral evolution). This distribution was not largely different from either in vivo fitness distributions recorded beyond primary infection or in vitro distributions that are observed without adaptive immunity, suggesting the intrinsic viral fitness distribution may drive evolution. Simulated phylogenetic trees also agree with independent data and illuminate how phylogenetic inference must consider viral and immune-cell population dynamics to gain accurate mechanistic insights.
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4
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Cao Y, Gao W, Caro L, Stone JA. Immune-viral dynamics modeling for SARS-CoV-2 drug development. Clin Transl Sci 2021; 14:2348-2359. [PMID: 34121337 PMCID: PMC8444857 DOI: 10.1111/cts.13099] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2021] [Revised: 05/03/2021] [Accepted: 05/18/2021] [Indexed: 12/13/2022] Open
Abstract
Coronavirus disease 2019 (COVID-19) global pandemic is caused by severe acute respiratory syndrome-coronavirus 2 (SARS-CoV-2) viral infection, which can lead to pneumonia, lung injury, and death in susceptible populations. Understanding viral dynamics of SARS-CoV-2 is critical for development of effective treatments. An Immune-Viral Dynamics Model (IVDM) is developed to describe SARS-CoV-2 viral dynamics and COVID-19 disease progression. A dataset of 60 individual patients with COVID-19 with clinical viral load (VL) and reported disease severity were assembled from literature. Viral infection and replication mechanisms of SARS-CoV-2, viral-induced cell death, and time-dependent immune response are incorporated in the model to describe the dynamics of viruses and immune response. Disease severity are tested as a covariate to model parameters. The IVDM was fitted to the data and parameters were estimated using the nonlinear mixed-effect model. The model can adequately describe individual viral dynamics profiles, with disease severity identified as a covariate on infected cell death rate. The modeling suggested that it takes about 32.6 days to reach 50% of maximum cell-based immunity. Simulations based on virtual populations suggested a typical mild case reaches VL limit of detection (LOD) by 13 days with no treatment, a moderate case by 17 days, and a severe case by 41 days. Simulations were used to explore hypothetical treatments with different initiation time, disease severity, and drug effects to demonstrate the usefulness of such modeling in informing decisions. Overall, the IVDM modeling and simulation platform enables simulations for viral dynamics and treatment efficacy and can be used to aid in clinical pharmacokinetic/pharmacodynamic (PK/PD) and dose-efficacy response analysis for COVID-19 drug development.
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Affiliation(s)
- Youfang Cao
- PPDM QP2Merck & Co., Inc.KenilworthNew JerseyUSA
| | - Wei Gao
- PPDM QP2Merck & Co., Inc.KenilworthNew JerseyUSA
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5
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Parra-Guillen ZP, Freshwater T, Cao Y, Mayawala K, Zalba S, Garrido MJ, de Alwis D, Troconiz IF. Mechanistic Modeling of a Novel Oncolytic Virus, V937, to Describe Viral Kinetic and Dynamic Processes Following Intratumoral and Intravenous Administration. Front Pharmacol 2021; 12:705443. [PMID: 34366859 PMCID: PMC8343024 DOI: 10.3389/fphar.2021.705443] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2021] [Accepted: 07/07/2021] [Indexed: 12/28/2022] Open
Abstract
V937 is an investigational novel oncolytic non-genetically modified Kuykendall strain of Coxsackievirus A21 which is in clinical development for the treatment of advanced solid tumor malignancies. V937 infects and lyses tumor cells expressing the intercellular adhesion molecule I (ICAM-I) receptor. We integrated in vitro and in vivo data from six different preclinical studies to build a mechanistic model that allowed a quantitative analysis of the biological processes of V937 viral kinetics and dynamics, viral distribution to tumor, and anti-tumor response elicited by V937 in human xenograft models in immunodeficient mice following intratumoral and intravenous administration. Estimates of viral infection and replication which were calculated from in vitro experiments were successfully used to describe the tumor response in vivo under various experimental conditions. Despite the predicted high clearance rate of V937 in systemic circulation (t1/2 = 4.3 min), high viral replication was observed in immunodeficient mice which resulted in tumor shrinkage with both intratumoral and intravenous administration. The described framework represents a step towards the quantitative characterization of viral distribution, replication, and oncolytic effect of a novel oncolytic virus following intratumoral and intravenous administrations in the absence of an immune response. This model may further be expanded to integrate the role of the immune system on viral and tumor dynamics to support the clinical development of oncolytic viruses.
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Affiliation(s)
- Zinnia P Parra-Guillen
- Department of Pharmaceutical Technology and Chemistry, School of Pharmacy and Nutrition, University of Navarra, Pamplona, Spain.,IdiSNA, Navarra Institute for Health Research, Pamplona, Spain
| | | | - Youfang Cao
- Merck & Co., Inc., Kenilworth, NJ, United States
| | | | - Sara Zalba
- Department of Pharmaceutical Technology and Chemistry, School of Pharmacy and Nutrition, University of Navarra, Pamplona, Spain.,IdiSNA, Navarra Institute for Health Research, Pamplona, Spain
| | - Maria J Garrido
- Department of Pharmaceutical Technology and Chemistry, School of Pharmacy and Nutrition, University of Navarra, Pamplona, Spain.,IdiSNA, Navarra Institute for Health Research, Pamplona, Spain
| | | | - Iñaki F Troconiz
- Department of Pharmaceutical Technology and Chemistry, School of Pharmacy and Nutrition, University of Navarra, Pamplona, Spain.,IdiSNA, Navarra Institute for Health Research, Pamplona, Spain
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6
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Wells CR, Cao Y, Durham DP, Byrareddy SN, Ansari AA, Ruddle NH, Townsend JP, Galvani AP, Perelson AS. Mechanistic basis of post-treatment control of SIV after anti-α4β7 antibody therapy. PLoS Comput Biol 2021; 17:e1009031. [PMID: 34106916 DOI: 10.1371/journal.pcbi.1009031] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2020] [Accepted: 05/02/2021] [Indexed: 02/07/2023] Open
Abstract
Treating macaques with an anti-α4β7 antibody under the umbrella of combination antiretroviral therapy (cART) during early SIV infection can lead to viral remission, with viral loads maintained at < 50 SIV RNA copies/ml after removal of all treatment in a subset of animals. Depletion of CD8+ lymphocytes in controllers resulted in transient recrudescence of viremia, suggesting that the combination of cART and anti-α4β7 antibody treatment led to a state where ongoing immune responses kept the virus undetectable in the absence of treatment. A previous mathematical model of HIV infection and cART incorporates immune effector cell responses and exhibits the property of two different viral load set-points. While the lower set-point could correspond to the attainment of long-term viral remission, attaining the higher set-point may be the result of viral rebound. Here we expand that model to include possible mechanisms of action of an anti-α4β7 antibody operating in these treated animals. We show that the model can fit the longitudinal viral load data from both IgG control and anti-α4β7 antibody treated macaques, suggesting explanations for the viral control associated with cART and an anti-α4β7 antibody treatment. This effective perturbation to the virus-host interaction can also explain observations in other nonhuman primate experiments in which cART and immunotherapy have led to post-treatment control or resetting of the viral load set-point. Interestingly, because the viral kinetics in the various treated animals differed—some animals exhibited large fluctuations in viral load after cART cessation—the model suggests that anti-α4β7 treatment could act by different primary mechanisms in different animals and still lead to post-treatment viral control. This outcome is nonetheless in accordance with a model with two stable viral load set-points, in which therapy can perturb the system from one set-point to a lower one through different biological mechanisms. Some macaques treated with an anti-α4β7 monoclonal antibody along with antiretroviral therapy during the early stages of simian immunodeficiency virus infection had their viral load become undetectable (below 50 SIV RNA copies/ml) after all treatment was stopped, whereas animals not given the antibody all had their viral loads rebound to high levels. Using a mathematical model, we examined four potential ways in which the antibody could have altered the balance between viral growth and immune control to maintain an undetectable viral load. We show that a shift to controlled infection can occur through multiple biologically reasonable mechanisms of action of the anti-α4β7 antibody.
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7
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Abstract
The CD8+ T cell noncytotoxic antiviral response (CNAR) was discovered during studies of asymptomatic HIV-infected subjects more than 30 years ago. In contrast to CD8+ T cell cytotoxic lymphocyte (CTL) activity, CNAR suppresses HIV replication without target cell killing. This activity has characteristics of innate immunity: it acts on all retroviruses and thus is neither epitope specific nor HLA restricted. The HIV-associated CNAR does not affect other virus families. It is mediated, at least in part, by a CD8+ T cell antiviral factor (CAF) that blocks HIV transcription. A variety of assays used to measure CNAR/CAF and the effects on other retrovirus infections are described. Notably, CD8+ T cell noncytotoxic antiviral responses have now been observed with other virus families but are mediated by different cytokines. Characterizing the protein structure of CAF has been challenging despite many biologic, immunologic, and molecular studies. It represents a low-abundance protein that may be identified by future next-generation sequencing approaches. Since CNAR/CAF is a natural noncytotoxic activity, it could provide promising strategies for HIV/AIDS therapy, cure, and prevention.
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Affiliation(s)
- Maelig G Morvan
- Division of Hematology/Oncology, Department of Medicine, University of California, San Francisco, San Francisco, California, USA
| | - Fernando C Teque
- Division of Hematology/Oncology, Department of Medicine, University of California, San Francisco, San Francisco, California, USA
| | | | - Jay A Levy
- Division of Hematology/Oncology, Department of Medicine, University of California, San Francisco, San Francisco, California, USA
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8
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Harper J, Huot N, Micci L, Tharp G, King C, Rascle P, Shenvi N, Wang H, Galardi C, Upadhyay AA, Villinger F, Lifson J, Silvestri G, Easley K, Jacquelin B, Bosinger S, Müller-Trutwin M, Paiardini M. IL-21 and IFNα therapy rescues terminally differentiated NK cells and limits SIV reservoir in ART-treated macaques. Nat Commun 2021; 12:2866. [PMID: 34001890 PMCID: PMC8129202 DOI: 10.1038/s41467-021-23189-7] [Citation(s) in RCA: 19] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2020] [Accepted: 04/08/2021] [Indexed: 12/13/2022] Open
Abstract
Unlike HIV infection, which progresses to AIDS absent suppressive anti-retroviral therapy, nonpathogenic infections in natural hosts, such African green monkeys, are characterized by a lack of gut microbial translocation and robust secondary lymphoid natural killer cell responses resulting in an absence of chronic inflammation and limited SIV dissemination in lymph node B-cell follicles. Here we report, using the pathogenic model of antiretroviral therapy-treated, SIV-infected rhesus macaques that sequential interleukin-21 and interferon alpha therapy generate terminally differentiated blood natural killer cells (NKG2a/clowCD16+) with potent human leukocyte antigen-E-restricted activity in response to SIV envelope peptides. This is in contrast to control macaques, where less differentiated, interferon gamma-producing natural killer cells predominate. The frequency and activity of terminally differentiated NKG2a/clowCD16+ natural killer cells correlates with a reduction of replication-competent SIV in lymph node during antiretroviral therapy and time to viral rebound following analytical treatment interruption. These data demonstrate that African green monkey-like natural killer cell differentiation profiles can be rescued in rhesus macaques to promote viral clearance in tissues.
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Affiliation(s)
- Justin Harper
- Division of Microbiology and Immunology, Yerkes National Primate Research Center, Emory University, Atlanta, GA, USA
| | - Nicolas Huot
- Institut Pasteur, Unité HIV, Inflammation et Persistance, Paris, France
| | - Luca Micci
- Division of Microbiology and Immunology, Yerkes National Primate Research Center, Emory University, Atlanta, GA, USA
| | - Gregory Tharp
- Nonhuman Primate Genomics Core, Yerkes National Primate Research Center, Emory University, Atlanta, GA, USA
| | - Colin King
- Division of Microbiology and Immunology, Yerkes National Primate Research Center, Emory University, Atlanta, GA, USA
| | - Philippe Rascle
- Institut Pasteur, Unité HIV, Inflammation et Persistance, Paris, France.,Université Paris Diderot, Sorbonne Paris Cité, Paris, France
| | - Neeta Shenvi
- Department of Biostatistics and Bioinformatics, Rollins School of Public Health, Emory University, Atlanta, GA, USA
| | - Hong Wang
- Division of Microbiology and Immunology, Yerkes National Primate Research Center, Emory University, Atlanta, GA, USA
| | - Cristin Galardi
- UNC HIV Cure Center and Department of Medicine, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA.,HIV Discovery, ViiV Healthcare, Research Triangle Park, NC, USA
| | - Amit A Upadhyay
- Nonhuman Primate Genomics Core, Yerkes National Primate Research Center, Emory University, Atlanta, GA, USA
| | - Francois Villinger
- Department of Biology, New Iberia Research Center, University of Louisiana at Lafayette, New Iberia, LA, USA
| | - Jeffrey Lifson
- AIDS and Cancer Virus Program, Frederick National Laboratory for Cancer Research, Frederick, MD, USA
| | - Guido Silvestri
- Division of Microbiology and Immunology, Yerkes National Primate Research Center, Emory University, Atlanta, GA, USA.,Department of Pathology and Laboratory Medicine, Emory University School of Medicine, Atlanta, GA, USA
| | - Kirk Easley
- Department of Biostatistics and Bioinformatics, Rollins School of Public Health, Emory University, Atlanta, GA, USA
| | | | - Steven Bosinger
- Division of Microbiology and Immunology, Yerkes National Primate Research Center, Emory University, Atlanta, GA, USA.,Nonhuman Primate Genomics Core, Yerkes National Primate Research Center, Emory University, Atlanta, GA, USA.,Department of Pathology and Laboratory Medicine, Emory University School of Medicine, Atlanta, GA, USA
| | | | - Mirko Paiardini
- Division of Microbiology and Immunology, Yerkes National Primate Research Center, Emory University, Atlanta, GA, USA. .,Department of Pathology and Laboratory Medicine, Emory University School of Medicine, Atlanta, GA, USA.
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9
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Okoye AA, Duell DD, Fukazawa Y, Varco-Merth B, Marenco A, Behrens H, Chaunzwa M, Selseth AN, Gilbride RM, Shao J, Edlefsen PT, Geleziunas R, Pinkevych M, Davenport MP, Busman-Sahay K, Nekorchuk M, Park H, Smedley J, Axthelm MK, Estes JD, Hansen SG, Keele BF, Lifson JD, Picker LJ. CD8+ T cells fail to limit SIV reactivation following ART withdrawal until after viral amplification. J Clin Invest 2021; 131:141677. [PMID: 33630764 DOI: 10.1172/jci141677] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2020] [Accepted: 02/23/2021] [Indexed: 12/15/2022] Open
Abstract
To define the contribution of CD8+ T cell responses to control of SIV reactivation during and following antiretroviral therapy (ART), we determined the effect of long-term CD8+ T cell depletion using a rhesusized anti-CD8β monoclonal antibody on barcoded SIVmac239 dynamics on stable ART and after ART cessation in rhesus macaques (RMs). Among the RMs with full CD8+ T cell depletion in both blood and tissue, there were no significant differences in the frequency of viral blips in plasma, the number of SIV RNA+ cells and the average number of RNA copies/infected cell in tissue, and levels of cell-associated SIV RNA and DNA in blood and tissue relative to control-treated RMs during ART. Upon ART cessation, both CD8+ T cell-depleted and control RMs rebounded in fewer than 12 days, with no difference in the time to viral rebound or in either the number or growth rate of rebounding SIVmac239M barcode clonotypes. However, effectively CD8+ T cell-depleted RMs showed a stable, approximately 2-log increase in post-ART plasma viremia relative to controls. These results indicate that while potent antiviral CD8+ T cell responses can develop during ART-suppressed SIV infection, these responses effectively intercept post-ART SIV rebound only after systemic viral replication, too late to limit reactivation frequency or the early spread of reactivating SIV reservoirs.
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Affiliation(s)
- Afam A Okoye
- Vaccine and Gene Therapy Institute and.,Oregon National Primate Research Center, Oregon Health & Science University, Beaverton, Oregon, USA
| | - Derick D Duell
- Vaccine and Gene Therapy Institute and.,Oregon National Primate Research Center, Oregon Health & Science University, Beaverton, Oregon, USA
| | - Yoshinori Fukazawa
- Vaccine and Gene Therapy Institute and.,Oregon National Primate Research Center, Oregon Health & Science University, Beaverton, Oregon, USA
| | - Benjamin Varco-Merth
- Vaccine and Gene Therapy Institute and.,Oregon National Primate Research Center, Oregon Health & Science University, Beaverton, Oregon, USA
| | - Alejandra Marenco
- Vaccine and Gene Therapy Institute and.,Oregon National Primate Research Center, Oregon Health & Science University, Beaverton, Oregon, USA
| | - Hannah Behrens
- Vaccine and Gene Therapy Institute and.,Oregon National Primate Research Center, Oregon Health & Science University, Beaverton, Oregon, USA
| | - Morgan Chaunzwa
- Vaccine and Gene Therapy Institute and.,Oregon National Primate Research Center, Oregon Health & Science University, Beaverton, Oregon, USA
| | - Andrea N Selseth
- Vaccine and Gene Therapy Institute and.,Oregon National Primate Research Center, Oregon Health & Science University, Beaverton, Oregon, USA
| | - Roxanne M Gilbride
- Vaccine and Gene Therapy Institute and.,Oregon National Primate Research Center, Oregon Health & Science University, Beaverton, Oregon, USA
| | - Jason Shao
- Statistical Center for HIV/AIDS Research and Prevention, Vaccine and Infectious Disease Division, Fred Hutchinson Cancer Research Center, Seattle, Washington, USA
| | - Paul T Edlefsen
- Statistical Center for HIV/AIDS Research and Prevention, Vaccine and Infectious Disease Division, Fred Hutchinson Cancer Research Center, Seattle, Washington, USA
| | | | - Mykola Pinkevych
- Kirby Institute for Infection and Immunity, University of New South Wales, Sydney, New South Wales, Australia
| | - Miles P Davenport
- Kirby Institute for Infection and Immunity, University of New South Wales, Sydney, New South Wales, Australia
| | - Kathleen Busman-Sahay
- Vaccine and Gene Therapy Institute and.,Oregon National Primate Research Center, Oregon Health & Science University, Beaverton, Oregon, USA
| | - Michael Nekorchuk
- Vaccine and Gene Therapy Institute and.,Oregon National Primate Research Center, Oregon Health & Science University, Beaverton, Oregon, USA
| | - Haesun Park
- Vaccine and Gene Therapy Institute and.,Oregon National Primate Research Center, Oregon Health & Science University, Beaverton, Oregon, USA
| | - Jeremy Smedley
- Vaccine and Gene Therapy Institute and.,Oregon National Primate Research Center, Oregon Health & Science University, Beaverton, Oregon, USA
| | - Michael K Axthelm
- Vaccine and Gene Therapy Institute and.,Oregon National Primate Research Center, Oregon Health & Science University, Beaverton, Oregon, USA
| | - Jacob D Estes
- Vaccine and Gene Therapy Institute and.,Oregon National Primate Research Center, Oregon Health & Science University, Beaverton, Oregon, USA
| | - Scott G Hansen
- Vaccine and Gene Therapy Institute and.,Oregon National Primate Research Center, Oregon Health & Science University, Beaverton, Oregon, USA
| | - Brandon F Keele
- AIDS and Cancer Virus Program, Frederick National Laboratory for Cancer Research, Frederick, Maryland, USA.,Leidos Biomedical Research, Inc., Frederick, Maryland, USA
| | - Jeffery D Lifson
- AIDS and Cancer Virus Program, Frederick National Laboratory for Cancer Research, Frederick, Maryland, USA.,Leidos Biomedical Research, Inc., Frederick, Maryland, USA
| | - Louis J Picker
- Vaccine and Gene Therapy Institute and.,Oregon National Primate Research Center, Oregon Health & Science University, Beaverton, Oregon, USA
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10
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Huot N, Rascle P, Tchitchek N, Wimmer B, Passaes C, Contreras V, Desjardins D, Stahl-Hennig C, Le Grand R, Saez-Cirion A, Jacquelin B, Müller-Trutwin M. Role of NKG2a/c +CD8 + T cells in pathogenic versus non-pathogenic SIV infections. iScience 2021; 24:102314. [PMID: 33870131 PMCID: PMC8040270 DOI: 10.1016/j.isci.2021.102314] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2020] [Revised: 02/12/2021] [Accepted: 03/11/2021] [Indexed: 01/10/2023] Open
Abstract
Some viruses have established an equilibrium with their host. African green monkeys (AGM) display persistent high viral replication in the blood and intestine during Simian immunodeficiency virus (SIV) infection but resolve systemic inflammation after acute infection and lack intestinal immune or tissue damage during chronic infection. We show that NKG2a/c+CD8+ T cells increase in the blood and intestine of AGM in response to SIVagm infection in contrast to SIVmac infection in macaques, the latter modeling HIV infection. NKG2a/c+CD8+ T cells were not expanded in lymph nodes, and CXCR5+NKG2a/c+CD8+ T cell frequencies further decreased after SIV infection. Genome-wide transcriptome analysis of NKG2a/c+CD8+ T cells from AGM revealed the expression of NK cell receptors, and of molecules with cytotoxic effector, gut homing, and immunoregulatory and gut barrier function, including CD73. NKG2a/c+CD8+ T cells correlated negatively with IL-23 in the intestine during SIVmac infection. The data suggest a potential regulatory role of NKG2a/c+CD8+ T cells in intestinal inflammation during SIV/HIV infections. Molecular determination of NKG2a/c+CD8+ T cells in two species of nonhuman primates Tissue distribution of NKG2a/c+CD8+ T cell is profoundly sculpted by SIV infections Intestinal NKG2a/c+CD8+ T cells correlated negatively with IL-23 in SIV infection NKG2a/c+CD8+ T cells might play a protective gut barrier function in HIV/SIV infection
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Affiliation(s)
- Nicolas Huot
- Institut Pasteur, Unité HIV, Inflammation et Persistance, 28 rue du Dr Roux, Paris 75015, France
| | - Philippe Rascle
- Institut Pasteur, Unité HIV, Inflammation et Persistance, 28 rue du Dr Roux, Paris 75015, France.,Université Paris Diderot, Sorbonne Paris Cité, Paris, France
| | - Nicolas Tchitchek
- Sorbonne Université, INSERM, Immunology-Immunopathology-Immunotherapy (i3), Paris, France
| | - Benedikt Wimmer
- Institut Pasteur, Unité HIV, Inflammation et Persistance, 28 rue du Dr Roux, Paris 75015, France
| | - Caroline Passaes
- Institut Pasteur, Unité HIV, Inflammation et Persistance, 28 rue du Dr Roux, Paris 75015, France
| | - Vanessa Contreras
- CEA-Université Paris Sud-Inserm, U1184, IDMIT Department, IBFJ, Fontenay-aux-Roses, France
| | - Delphine Desjardins
- CEA-Université Paris Sud-Inserm, U1184, IDMIT Department, IBFJ, Fontenay-aux-Roses, France
| | - Christiane Stahl-Hennig
- Deutsches Primatenzentrum - Leibniz Institut für Primatenforschung, Unit of Infection Models, Göttingen, Germany
| | - Roger Le Grand
- CEA-Université Paris Sud-Inserm, U1184, IDMIT Department, IBFJ, Fontenay-aux-Roses, France
| | - Asier Saez-Cirion
- Institut Pasteur, Unité HIV, Inflammation et Persistance, 28 rue du Dr Roux, Paris 75015, France
| | - Beatrice Jacquelin
- Institut Pasteur, Unité HIV, Inflammation et Persistance, 28 rue du Dr Roux, Paris 75015, France
| | - Michaela Müller-Trutwin
- Institut Pasteur, Unité HIV, Inflammation et Persistance, 28 rue du Dr Roux, Paris 75015, France
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11
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Singh AP, Zheng X, Lin-Schmidt X, Chen W, Carpenter TJ, Zong A, Wang W, Heald DL. Development of a quantitative relationship between CAR-affinity, antigen abundance, tumor cell depletion and CAR-T cell expansion using a multiscale systems PK-PD model. MAbs 2021; 12:1688616. [PMID: 31852337 PMCID: PMC6927769 DOI: 10.1080/19420862.2019.1688616] [Citation(s) in RCA: 59] [Impact Index Per Article: 19.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
The development of mechanism-based, multiscale pharmacokinetic–pharmacodynamic (PK-PD) models for chimeric antigen receptor (CAR)-T cells is needed to enable investigation of in vitro and in vivo correlation of CAR-T cell responses and to facilitate preclinical-to-clinical translation. Toward this goal, we first developed a cell-level in vitro PD model that quantitatively characterized CAR-T cell-induced target cell depletion, CAR-T cell expansion and cytokine release. The model accounted for key drug-specific (CAR-affinity, CAR-densities) and system-specific (antigen densities, E:T ratios) variables and was able to characterize comprehensive in vitro datasets from multiple affinity variants of anti-EGFR and anti-HER2 CAR-T cells. Next, a physiologically based PK (PBPK) model was developed to simultaneously characterize the biodistribution of untransduced T-cells, anti-EGFR CAR-T and anti-CD19 CAR-T cells in xenograft -mouse models. The proposed model accounted for the engagement of CAR-T cells with tumor cells at the site of action. Finally, an integrated PBPK-PD relationship was established to simultaneously characterize expansion of CAR-T cells and tumor growth inhibition (TGI) in xenograft mouse model, using datasets from anti-BCMA, anti-HER2, anti-CD19 and anti-EGFR CAR-T cells. Model simulations provided potential mechanistic insights toward the commonly observed multiphasic PK profile (i.e., rapid distribution, expansion, contraction and persistence) of CAR-T cells in the clinic. Model simulations suggested that CAR-T cells may have a steep dose-exposure relationship, and the apparent Cmax upon CAR-T cell expansion in blood may be more sensitive to patient tumor-burden than CAR-T dose levels. Global sensitivity analysis described the effect of other drug-specific parameters toward CAR-T cell expansion and TGI. The proposed modeling framework will be further examined with the clinical PK and PD data, and the learnings can be used to inform design and development of future CAR-T therapies.
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Affiliation(s)
- Aman P Singh
- Discovery and Translational Research, Biologics Development Sciences, Janssen Biotherapeutics, Spring House, PA, USA
| | - Xirong Zheng
- Discovery and Translational Research, Biologics Development Sciences, Janssen Biotherapeutics, Spring House, PA, USA
| | | | - Wenbo Chen
- Discovery and Translational Research, Biologics Development Sciences, Janssen Biotherapeutics, Spring House, PA, USA
| | - Thomas J Carpenter
- Discovery and Translational Research, Biologics Development Sciences, Janssen Biotherapeutics, Spring House, PA, USA
| | - Alice Zong
- Discovery and Translational Research, Biologics Development Sciences, Janssen Biotherapeutics, Spring House, PA, USA
| | - Weirong Wang
- Clinical Pharmacology and Pharmacometrics, Janssen Research and Development, Spring House, PA, USA
| | - Donald L Heald
- Discovery and Translational Research, Biologics Development Sciences, Janssen Biotherapeutics, Spring House, PA, USA
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12
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van Dorp CH, Conway JM, Barouch DH, Whitney JB, Perelson AS. Models of SIV rebound after treatment interruption that involve multiple reactivation events. PLoS Comput Biol 2020; 16:e1008241. [PMID: 33001979 PMCID: PMC7529301 DOI: 10.1371/journal.pcbi.1008241] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2020] [Accepted: 08/12/2020] [Indexed: 02/07/2023] Open
Abstract
In order to assess the efficacy of novel HIV-1 treatments leading to a functional cure, the time to viral rebound is frequently used as a surrogate endpoint. The longer the time to viral rebound, the more efficacious the therapy. In support of such an approach, mathematical models serve as a connection between the size of the latent reservoir and the time to HIV-1 rebound after treatment interruption. The simplest of such models assumes that a single successful latent cell reactivation event leads to observable viremia after a period of exponential viral growth. Here we consider a generalization developed by Pinkevych et al. and Hill et al. of this simple model in which multiple reactivation events can occur, each contributing to the exponential growth of the viral load. We formalize and improve the previous derivation of the dynamics predicted by this model, and use the model to estimate relevant biological parameters from SIV rebound data. We confirm a previously described effect of very early antiretroviral therapy (ART) initiation on the rate of recrudescence and the viral load growth rate after treatment interruption. We find that every day ART initiation is delayed results in a 39% increase in the recrudescence rate (95% credible interval: [18%, 62%]), and a 11% decrease of the viral growth rate (95% credible interval: [4%, 20%]). We show that when viral rebound occurs early relative to the viral load doubling time, a model with multiple successful reactivation events fits the data better than a model with only a single successful reactivation event.
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Affiliation(s)
- Christiaan H. van Dorp
- Theoretical Biology and Biophysics (T-6), Los Alamos National Laboratory, Los Alamos, New Mexico, United States of America
| | - Jessica M. Conway
- Department of Mathematics and Center for Infectious Disease Dynamics, Pennsylvania State University, University Park, Pennsylvania, United States of America
| | - Dan H. Barouch
- Center for Virology and Vaccine Research, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts, United States of America
- Ragon Institute of MGH, MIT, and Harvard, Cambridge, Massachusetts, United States of America
| | - James B. Whitney
- Center for Virology and Vaccine Research, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts, United States of America
- Ragon Institute of MGH, MIT, and Harvard, Cambridge, Massachusetts, United States of America
| | - Alan S. Perelson
- Theoretical Biology and Biophysics (T-6), Los Alamos National Laboratory, Los Alamos, New Mexico, United States of America
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13
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Kristoff J, Rinaldo CR, Mailliard RB. Role of Dendritic Cells in Exposing Latent HIV-1 for the Kill. Viruses 2019; 12:E37. [PMID: 31905690 DOI: 10.3390/v12010037] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2019] [Revised: 12/19/2019] [Accepted: 12/24/2019] [Indexed: 12/11/2022] Open
Abstract
The development of effective yet nontoxic strategies to target the latent human immunodeficiency virus-1 (HIV-1) reservoir in antiretroviral therapy (ART)-suppressed individuals poses a critical barrier to a functional cure. The ‘kick and kill’ approach to HIV eradication entails proviral reactivation during ART, coupled with generation of cytotoxic T lymphocytes (CTLs) or other immune effectors equipped to eliminate exposed infected cells. Pharmacological latency reversal agents (LRAs) that have produced modest reductions in the latent reservoir ex vivo have not impacted levels of proviral DNA in HIV-infected individuals. An optimal cure strategy incorporates methods that facilitate sufficient antigen exposure on reactivated cells following the induction of proviral gene expression, as well as the elimination of infected targets by either polyfunctional HIV-specific CTLs or other immune-based strategies. Although conventional dendritic cells (DCs) have been used extensively for the purpose of inducing antigen-specific CTL responses in HIV-1 clinical trials, their immunotherapeutic potential as cellular LRAs has been largely ignored. In this review, we discuss the challenges associated with current HIV-1 eradication strategies, as well as the unharnessed potential of ex vivo-programmed DCs for both the ‘kick and kill’ of latent HIV-1.
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14
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Li G, Zhang Z, Reszka-Blanco N, Li F, Chi L, Ma J, Jeffrey J, Cheng L, Su L. Specific Activation In Vivo of HIV-1 by a Bromodomain Inhibitor from Monocytic Cells in Humanized Mice under Antiretroviral Therapy. J Virol 2019; 93:e00233-19. [PMID: 30971469 DOI: 10.1128/JVI.00233-19] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2019] [Accepted: 03/26/2019] [Indexed: 11/20/2022] Open
Abstract
Combination antiretroviral therapy (cART) effectively suppresses HIV-1 replication and enables HIV‑infected individuals to live long, productive lives. However, the persistence of HIV-1 reservoirs of both T and myeloid cells with latent or low-replicating HIV-1 in patients under cART makes HIV-1 infection an incurable disease. Recent studies have focused on the development of strategies to activate and purge these reservoirs. Bromodomain and extraterminal domain proteins (BETs) are epigenetic readers involved in modulating gene expression. Several bromodomain inhibitors (BETi) are reported to activate viral transcription in vitro in HIV-1 latency cell lines in a P-TEFb (CDK9/cyclin T1)-dependent manner. Little is known about BETi efficacy in activating HIV-1 reservoir cells under cART in vivo Here we report that a BETi (I-BET151) efficiently activated HIV-1 reservoirs under effective cART in humanized mice in vivo Interestingly, I-BET151 during suppressive cART in vivo activated HIV-1 gene expression only in monocytic cells and not in CD4+ T cells. We further demonstrate that BETi preferentially enhanced HIV-1 gene expression in monocytic cells rather than in T cells and that whereas CDK9 was involved in activating HIV-1 by I-BET151 in both monocytic and T cells, CDK2 enhanced HIV-1 transcription in monocytic cells but inhibited it in T cells. Our findings reveal a role for CDK2 in differential modulation of HIV-1 gene expression in myeloid cells and in T cells and provide a novel strategy to reactivate monocytic reservoirs with BETi during cART.IMPORTANCE Bromodomain inhibitors have been reported to activate HIV-1 transcription in vitro, but their effect on activation of HIV-1 reservoirs during cART in vivo is unclear. We found that BETi (I-BET151) treatment reactivated HIV-1 gene expression in humanized mice during suppressive cART. Interestingly, I-BET151 preferentially reactivated HIV-1 gene expression in monocytic cells, but not in CD4 T cells, in cART-treated mice. Furthermore, I-BET151 significantly increased HIV-1 transcription in monocytic cells, but not in HIV-1-infected CD4 T cells, via CDK2-dependent mechanisms. Our findings suggest that BETi can preferentially activate monocytic HIV-1 reservoir cells and that a combination of reservoir activation agents targeting different cell types and pathways is needed to achieve reactivation of different HIV-1 reservoir cells during cART.
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15
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Delannoy A, Poirier M, Bell B. Cat and Mouse: HIV Transcription in Latency, Immune Evasion and Cure/Remission Strategies. Viruses 2019; 11:E269. [PMID: 30889861 DOI: 10.3390/v11030269] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2019] [Revised: 03/04/2019] [Accepted: 03/13/2019] [Indexed: 12/13/2022] Open
Abstract
There is broad scientific and societal consensus that finding a cure for HIV infection must be pursued. The major barrier to achieving a cure for HIV/AIDS is the capacity of the HIV virus to avoid both immune surveillance and current antiretroviral therapy (ART) by rapidly establishing latently infected cell populations, termed latent reservoirs. Here, we provide an overview of the rapidly evolving field of HIV cure/remission research, highlighting recent progress and ongoing challenges in the understanding of HIV reservoirs, the role of HIV transcription in latency and immune evasion. We review the major approaches towards a cure that are currently being explored and further argue that small molecules that inhibit HIV transcription, and therefore uncouple HIV gene expression from signals sent by the host immune response, might be a particularly promising approach to attain a cure or remission. We emphasize that a better understanding of the game of "cat and mouse" between the host immune system and the HIV virus is a crucial knowledge gap to be filled in both cure and vaccine research.
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16
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Baral S, Raja R, Sen P, Dixit NM. Towards multiscale modeling of the CD8 + T cell response to viral infections. Wiley Interdiscip Rev Syst Biol Med 2019; 11:e1446. [PMID: 30811096 PMCID: PMC6614031 DOI: 10.1002/wsbm.1446] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/24/2018] [Revised: 01/23/2019] [Accepted: 01/28/2019] [Indexed: 12/22/2022]
Abstract
The CD8+ T cell response is critical to the control of viral infections. Yet, defining the CD8+ T cell response to viral infections quantitatively has been a challenge. Following antigen recognition, which triggers an intracellular signaling cascade, CD8+ T cells can differentiate into effector cells, which proliferate rapidly and destroy infected cells. When the infection is cleared, they leave behind memory cells for quick recall following a second challenge. If the infection persists, the cells may become exhausted, retaining minimal control of the infection while preventing severe immunopathology. These activation, proliferation and differentiation processes as well as the mounting of the effector response are intrinsically multiscale and collective phenomena. Remarkable experimental advances in the recent years, especially at the single cell level, have enabled a quantitative characterization of several underlying processes. Simultaneously, sophisticated mathematical models have begun to be constructed that describe these multiscale phenomena, bringing us closer to a comprehensive description of the CD8+ T cell response to viral infections. Here, we review the advances made and summarize the challenges and opportunities ahead. This article is categorized under: Analytical and Computational Methods > Computational Methods Biological Mechanisms > Cell Fates Biological Mechanisms > Cell Signaling Models of Systems Properties and Processes > Mechanistic Models.
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Affiliation(s)
- Subhasish Baral
- Department of Chemical Engineering, Indian Institute of Science, Bangalore, India
| | - Rubesh Raja
- Department of Chemical Engineering, Indian Institute of Science, Bangalore, India
| | - Pramita Sen
- Department of Chemical Engineering, Indian Institute of Science, Bangalore, India
| | - Narendra M Dixit
- Department of Chemical Engineering, Indian Institute of Science, Bangalore, India.,Centre for Biosystems Science and Engineering, Indian Institute of Science, Bangalore, India
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17
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Cao Y, Lei X, Ribeiro RM, Perelson AS, Liang J. Probabilistic control of HIV latency and transactivation by the Tat gene circuit. Proc Natl Acad Sci U S A 2018; 115:12453-8. [PMID: 30455316 DOI: 10.1073/pnas.1811195115] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
The reservoir of HIV latently infected cells is the major obstacle for eradication of HIV infection. The "shock-and-kill" strategy proposed earlier aims to reduce the reservoir by activating cells out of latency. While the intracellular HIV Tat gene circuit is known to play important roles in controlling latency and its transactivation in HIV-infected cells, the detailed control mechanisms are not well understood. Here we study the mechanism of probabilistic control of the latent and the transactivated cell phenotypes of HIV-infected cells. We reconstructed the probability landscape, which is the probability distribution of the Tat gene circuit states, by directly computing the exact solution of the underlying chemical master equation. Results show that the Tat circuit exhibits a clear bimodal probability landscape (i.e., there are two distinct probability peaks, one associated with the latent cell phenotype and the other with the transactivated cell phenotype). We explore potential modifications to reactions in the Tat gene circuit for more effective transactivation of latent cells (i.e., the shock-and-kill strategy). Our results suggest that enhancing Tat acetylation can dramatically increase Tat and viral production, while increasing the Tat-transactivation response binding affinity can transactivate latent cells more rapidly than other manipulations. Our results further explored the "block and lock" strategy toward a functional cure for HIV. Overall, our study demonstrates a general approach toward discovery of effective therapeutic strategies and druggable targets by examining control mechanisms of cell phenotype switching via exactly computed probability landscapes of reaction networks.
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