Untreated HIV infection is characterized by generalized immune activation, T cell dysfunction, and ultimately the exhaustion of HIV-specific CD8 T cell responses. Durable virus suppression resulting from anti-retroviral therapy (ART) is associated with greatly improved immune function, but some phenotypic and functional abnormalities persist even after years of suppressive ART. We have observed that, relative to HIV-seronegative individuals, CD8 T cells from HIV+ participants on ART are skewed toward a more effector-like (T-bethigh Eomeslow) phenotype and have significantly reduced proliferative capacity in response to antigenic stimulation. Metabolic pathways play a key role in shaping T cell maturation, phenotype, and function, and the ability to produce ATP via both glycolytic and oxidative phosphorylation (mitochondrial) pathways is critical to T cell function and longevity. However, whether underlying metabolic abnormalities contribute to residual CD8 T cell dysfunction in HIV+ individuals on ART has not been fully explored. Here we compare the metabolic phenotype of T cells from HIV+ participants on ART with those from HIV-seronegative participants. We are using MitoTracker® dyes to assess mitochondrial mass and polarization in T cell memory subsets, ex vivo and in response to antigen, and measuring expression of the glucose transporter GLUT1 and the mitochondrial biogenesis master regulator PGC-1α in different CD8 T cell effector subsets. Our findings will inform whether phenotypic and functional abnormalities in CD8 T cells from HIV+ individuals on ART reflect underlying metabolic dysfunction and if metabolic interventions could improve T cell function.
In HIV-infected individuals, anti-retroviral therapy (ART) is effective in maintaining low viral loads, restoring CD4+ T cell counts, and prolonging life. However, chronic inflammation and immune dysfunction persist even after years of successful ART. Previous studies have suggested that early initiation of ART may result in improved immune reconstitution, but whether more rapid suppression of viral load during early treatment also improves immunological outcomes is unknown. In this study we compare the effects of two regimens initiated during acute infection on T cell phenotype and function. Regimen 1 (n=30) is a non-nucleoside reverse transcriptase inhibitor (NNRTI)-based regimen and Regimen 2 (n=30) combines an integrase strand transfer inhibitor (INSTI) with nucleoside reverse transcriptase inhibitors (NRTIs). NRTIs and NNRTIs inhibit reverse transcription of viral RNA to DNA in the infected cell, while INSTIs block integration of viral DNA into the host genome. Since Regimen 2 targets multiple stages of the viral life cycle, we hypothesize that more rapid viral suppression may be achieved with this treatment schedule. In a cross-sectional study performed 96 weeks after treatment initiation, we are comparing the effects of the two regimens on T cell activation (CD25, CD69, CD38, HLA-DR), exhaustion (PD-1, Tim-3, CD160, T-bet, Eomes), and proliferation using standardized flow cytometry panels. This study will provide valuable insights into the relationship between viral decay kinetics and immune preservation during acute infection, informing the design of future ART regimens.
CD8+ T cell immunity is essential to the control of HIV viremia. We examined the safety and immunogenicity of MVA-vectored vaccines expressing highly conserved HIV regions in a first-in-man Phase I study in people living with HIV on ART. Participants received a single intramuscular dose of MVA.tHIVconsv3 (M3), MVA.tHIVconsv4 (M4), combined M3+M4 or saline in a 7:7:7:3 ratio. M3 and M4 span the same 6 HIV regions but differ by approximately 10% of amino acids; a design to increase vaccine coverage of circulating HIV variants. We employed ex vivo IFN-g ELISpot assays to measure changes in HIV-specific T cell magnitude and breadth to M3 and/or M4 immunogens following vaccination. We also examined whether M3, M4 or M3+M4 vaccination increased the ability of CD8+ T cells inhibit HIV in vitro replication. The M&M study is fully enrolled but presently is blinded. Analysis of blinded data show that vaccination was safe and well tolerated. Vaccination induced strong increases in the T cell response to M3, M4 vaccine immunogens producing a 2- to 18-fold increase in magnitude in 16/20 participants tested to date. M3/M4-specific T cell breadth also increased across participants. Vaccine-associated T cell responses mostly remained elevated (>2-fold increase) for at least 70 days post-vaccination visit. Vaccination was also associated with clear and sustained increases in in vitro virus inhibition. The percentage of the total HIV T cell response targeting conserved HIV regions in participants increased on average from 40 to 60% post-vaccination, suggesting M3/M4/M3+4 vaccination successfully produced a sustained shift in T cell immunodominance. Unblinded data will be presented at this meeting. Supported by U01AI131310
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