Elevated glycolysis imparts functional ability to CD8+ T cells in HIV infection.

The mechanisms inducing exhaustion of HIV-specific CD8+ T cells are not fully understood. Metabolic programming directly influences T-cell differentiation, effector function, and memory. We evaluated metabolic profiles of ex vivo CD8+ T cells in HIV-infected individuals. The baseline oxygen consumption rate of CD8+ T cells was elevated in all infected individuals and CD8+ T cells were working at maximal respiratory capacity. The baseline glycolysis rate was enhanced only during early untreated HIV and in viral controllers, but glycolytic capacity was conserved at all stages of infection. CD8+ T-cell mTOR activity was found to be reduced. Enhanced glycolysis was crucial for HIV-specific killing of CD8+ T cells. CD8+ T-cell cytoplasmic GAPDH content was reduced in HIV, but less in early infection and viral controllers. Thus, CD8+ T-cell exhaustion in HIV is characterized by reduced glycolytic activity, enhanced OXPHOS demands, dysregulated mTOR, and reduced cytoplasmic GAPDH. These data provide potential metabolic strategies to reverse CD8+ T-cell dysfunction in HIV.

HIV Subtype and Nef-Mediated Immune Evasion Function Correlate with Viral Reservoir Size in Early-Treated Individuals.

The HIV accessory protein Nef modulates key immune evasion and pathogenic functions, and its encoding gene region exhibits high sequence diversity. Given the recent identification of early HIV-specific adaptive immune responses as novel correlates of HIV reservoir size, we hypothesized that viral factors that facilitate the evasion of such responses-namely, Nef genetic and functional diversity-might also influence reservoir establishment and/or persistence. We isolated baseline plasma HIV RNA-derived nef clones from 30 acute/early-infected individuals who participated in a clinical trial of early combination antiretroviral therapy (cART) (<6 months following infection) and assessed each Nef clone's ability to downregulate CD4 and human leukocyte antigen (HLA) class I in vitro We then explored the relationships between baseline clinical, immunological, and virological characteristics and the HIV reservoir size measured 48 weeks following initiation of suppressive cART (where the reservoir size was quantified in terms of the proviral DNA loads as well as the levels of replication-competent HIV in CD4+ T cells). Maximal within-host Nef-mediated downregulation of HLA, but not CD4, correlated positively with post-cART proviral DNA levels (Spearman's R = 0.61, P = 0.0004) and replication-competent reservoir sizes (Spearman's R = 0.36, P = 0.056) in univariable analyses. Furthermore, the Nef-mediated HLA downregulation function was retained in final multivariable models adjusting for established clinical and immunological correlates of reservoir size. Finally, HIV subtype B-infected persons (n = 25) harbored significantly larger viral reservoirs than non-subtype B-infected persons (2 infected with subtype CRF01_AE and 3 infected with subtype G). Our results highlight a potentially important role of viral factors-in particular, HIV subtype and accessory protein function-in modulating viral reservoir establishment and persistence.IMPORTANCE While combination antiretroviral therapies (cART) have transformed HIV infection into a chronic manageable condition, they do not act upon the latent HIV reservoir and are therefore not curative. As HIV cure or remission should be more readily achievable in individuals with smaller HIV reservoirs, achieving a deeper understanding of the clinical, immunological, and virological determinants of reservoir size is critical to eradication efforts. We performed a post hoc analysis of 30 participants of a clinical trial of early cART who had previously been assessed in detail for their clinical, immunological, and reservoir size characteristics. We observed that the HIV subtype and autologous Nef-mediated HLA downregulation function correlated with the viral reservoir size measured approximately 1 year post-cART initiation. Our findings highlight virological characteristics-both genetic and functional-as possible novel determinants of HIV reservoir establishment and persistence.

Comprehensive Cross-Clade Characterization of Antibody-Mediated Recognition, Complement-Mediated Lysis, and Cell-Mediated Cytotoxicity of HIV-1 Envelope-Specific Antibodies toward Eradication of the HIV-1 Reservoir.

Immunotherapy with passive administration of broadly neutralizing HIV-1 envelope-specific antibodies (bnAbs) in the setting of established infection in vivo has yielded mixed results. The contribution of different antibodies toward the direct elimination of infected cells is poorly understood. In this study, we determined the ability of 12 well-characterized anti-HIV-1 neutralizing antibodies to recognize and eliminate primary CD4 T cells infected with HIV-1 belonging to clades A, B, C, and D, via antibody-dependent complement-mediated lysis (ADCML) and antibody-dependent cell-mediated cytotoxicity (ADCC), in vitro We further tested unique combinations of these antibodies to determine the optimal antibody cocktails to be tested in future clinical trials. We report that antibody binding to infected CD4 T cells is highly variable and correlates with ADCML and ADCC processes. Particularly, antibodies targeting the envelope glycan shield (2G12) and V1/V2 site (PG9, PG16, and PGT145) are best at recognizing HIV-1-infected CD4 T cells. However, only PG9 and PG16 and their combinations with other bnAbs sufficiently induced the elimination of HIV-1-infected CD4 T cells by ADCML, ADCC, or both. Notably, CD4 binding site antibodies VRC01, 3BNC117, and NIH45-46 G54W did not exhibit recognition of infected cells and were unable to induce their killing. Future trials geared toward the development of a cure for HIV/AIDS should incorporate V1/V2 antibodies for maximal clearance of infected cells. With the use of only primary immune cells, we conducted a comprehensive cross-clade physiological analysis to aid the direction of antibodies as therapeutics toward the development of a cure for HIV/AIDS.IMPORTANCE Several antibodies capable of neutralizing the majority of circulating HIV-1 strains have been identified to date and have been shown to prevent infection in animal models. However, the use of combinations of such broadly neutralizing antibodies (bnAbs) for the treatment and eradication of HIV-1 in infected humans remains uncertain. In this study, we tested the ability of bnAbs to directly recognize and eliminate primary human CD4 T cells infected with diverse HIV-1 strains representative of the global epidemic by antibody-dependent pathways. We also tested several combinations of bnAbs in our assays in order to maximize the clearance of infected cells. We show that the ability of bnAbs to identify and kill infected cells is highly variable and that only a few of them are able to exert this function. Our data will help guide the formulation of bnAbs to test in future human trials aimed at the development of a cure.

HIV-Specific Granzyme B-Secreting but Not Gamma Interferon-Secreting T Cells Are Associated with Reduced Viral Reservoirs in Early HIV Infection.

A major barrier to a human immunodeficiency virus type 1 (HIV-1) infection cure is the establishment of a viral reservoir in spite of combined antiretroviral therapy (cART). It is unclear how HIV-specific cytotoxic T lymphocytes (CTLs) influence the size of the reservoir in early HIV infection. Twenty-eight subjects with early HIV infection were recruited to receive cART and followed for 48 weeks. HIV reservoirs in peripheral CD4+ T cells measured by cell-associated proviral DNA and viral outgrowth cultures were determined at baseline and after 48 weeks of cART. At baseline, granzyme B and gamma interferon (IFN-γ) enzyme-linked immunosorbent spot (ELISpot) assays were performed with peptides spanning the HIV proteome. All subjects had detectable HIV-specific granzyme B and IFN-γ responses at baseline. The quantity and specificity of granzyme B responses did not correlate with IFN-γ responses. For granzyme B, Tat/Rev was the most dominant whereas for IFN-γ, Gag predominated. HIV-specific granzyme B T cell responses negatively correlated with HIV proviral loads at baseline and at 48 weeks and with replication-competent viral infectious units per million (IUPM) CD4+ T cells at baseline but not significantly at 48 weeks. Tat/Rev-, Env-, Gag-, and Vif-specific granzyme B responses correlated most strongly with reservoir control. There was no correlation of HIV-specific IFN-γ responses with reservoir size at baseline or at 48 weeks. The majority of granzyme B responses were contributed by CD8+ T cells. Thus, our findings suggest that the induction of potent granzyme B-producing CTLs to Tat, Rev, Env, Gag, and Vif during early infection may be able to prevent the establishment of a large viral reservoir, thereby facilitating a reduced HIV burden.IMPORTANCE A major barrier to the cure of human immunodeficiency virus type 1 (HIV-1) infection is the establishment of a viral reservoir that must be significantly reduced or eradicated entirely to enable a cure. Combined antiretroviral therapy (cART) alone is unable to clear this viral reservoir. It has been shown that CD8+ cytotoxic T lymphocytes (CTLs) are important in controlling early HIV infection by reducing plasma viremia. However, it is not known if these HIV-specific CTLs influence the establishment of the viral reservoir in early HIV infection. We show that HIV-specific granzyme B responses targeting HIV Tat/Rev, Env, Gag, and Vif, but not IFN-γ responses, are associated with reduced virus reservoirs at baseline and at 48 weeks of cART. These findings shed light on the nature of the effector CTL response that might limit reservoir size with implications for cure research and HIV vaccines.