CROI 2025 Abstract eBook

Abstract eBook

Poster Abstracts

405

Robust CD8+ T-Cell Proliferation and Stem-Like Memory Phenotype Linked to HIV Post-Treatment Control Charles Crain 1 , Behzad Etemad 2 , Prerana Shrestha 2 , Steven G. Deeks 3 , Jonathan Li 2 , Rachel Rutishauser 3 , Gaurav D. Gaiha 1 1 Ragon Institute of MGH, MIT and Harvard, Cambridge, MA, USA, 2 Brigham and Women's Hospital, Boston, MA, USA, 3 University of California San Francisco, San Francisco, CA, USA Background: Post-treatment controllers (PTCs) of HIV control viremia to low or undetectable levels following discontinuation of ART. Previous studies have suggested a lack of association between ex vivo HIV-specific CD8 + T cell responses and post-treatment control. Here we extended beyond ex vivo evaluations to assess the proliferative capacity of HIV-specific CD8 + T cell responses in PTCs and the immune phenotypes of these responses. Methods: We evaluated HIV-specific CD8 + T cell responses of 6 PTCs, in comparison to 6 previously ART-treated spontaneous controllers (TCs) and 11 non-controllers (NCs), both pre- and post-treatment interruption (TI). Both PTC and TC were defined as having plasma viral loads <10,000 copies/mL for at least 52 weeks post-TI, with TC additionally having a viral load <10,000 copies/ mL at the time of ART initiation. PBMC from each participant were stimulated with overlapping peptide pools to the HIV proteins Gag, Pol, Nef, and Env in two stimulation conditions – a short 6-hour stimulation to identify ex vivo reactive T cells (pre-expansion) and a similar 6-hour restimulation following a 6-day stimulation to identify expanded antigen-specific cells. Samples were analyzed by surface/intracellular cytokine staining and flow cytometry. HIV-specific CD8 + T cells were identified as those double-positive for interferon (IFN)-γ and CD107a. Results: As with prior studies, there was no significant difference in the frequency of ex vivo pre-expansion HIV-specific CD8 + T cells between the three groups post-TI. However, evaluation of proliferative capacity revealed a significant and marked fold-expansion of HIV-specific cells in PTC following 6-day peptide stimulation compared to NC (P<0.01). Phenotypic analysis of pre expansion HIV-specific CD8 + T cells revealed that PTC had a significantly higher proportion expressing the stem-like memory markers TCF1 and CD127 than NC (P<0.05). Conversely, HIV-specific CD8 + T cells from NC had higher expression of TOX as well as the inhibitory receptor PD-1 (P<0.01 and P<0.05). Notably, NC also displayed this exhausted HIV-specific CD8 + T cell phenotype pre-TI while ART-suppressed. Conclusions: HIV-specific CD8 + T cells from PTC demonstrated enhanced proliferative capacity and exhibited a stem-like memory phenotype, whereas NC had responses characterized by immune exhaustion. These findings establish key correlates of post-treatment control which can be leveraged as biomarkers to evaluate therapeutic vaccines and immunotherapies for HIV cure. HIV-Infection Does Not Generally Confer Higher Resistance to CTL-Mediated Lysis Niklas Bachmann 1 , Bailey Kim 2 , Steven G. Deeks 3 , Robert F. Siliciano 1 1 The Johns Hopkins University School of Medicine, Baltimore, MD, USA, 2 The Johns Hopkins University, Baltimore, MD, USA, 3 University of California San Francisco, San Francisco, CA, USA Background: While current antiretroviral treatment regimens can reliably prevent new infection events in people living with HIV (PLWH), they cannot actively eliminate the persistent population of CD4 T cells harboring intact provirus that can give rise to viral rebound if treatment is interrupted. Various approaches to HIV cure rely on the elimination of this reservoir through cytotoxic T lymphocytes (CTLs). However, some studies have suggested that HIV-infection might confer some level of intrinsic resistance to CTL-mediated lysis through various mechanisms such as the upregulation of anti-apoptotic factors. Here, we show that the rate of lysis did not differ between primary CD4 T cells that are uninfected, harboring intact HIV provirus, or actively expressing an HIV reporter construct. Methods: We performed co-culture killing assays using either primary CD4+ T cells of 7 aviremic PLWH or healthy donor CD4+ T cells that were spinoculated with different NL4-3 HIV GFP-reporter constructs, with autologous CD8+ T cells and CTL-engaging single-chain diabodies specific for a exogenous peptides in the context of HLA-A2 or HLA-E. CD4+ T cells were converted into target cells by pulsing them with saturating concentrations of the respective peptides. Following the co-culture, killing was assessed via flow cytometry. The frequency of HIV-infected cells before and after the co-culture was determined using the intact proviral DNA assay in the case of primary cells from PLWH, or by quantifying the frequency of GFP+ reporter cells for spinoculated CD4 T cells.

Results: In 6 of the 7 study participants, we did not see any enrichment for cells harboring intact provirus over the course of the co-culture. When testing healthy donor cells expressing NL4-3 reporter virus using an HLA-A2 antigen, we saw nef-dependent enrichment for actively infected cells. Surface HLA staining showed that in cells infected with nef-sufficient virus, HLA-A2, but not HLA-E, is downregulated. When we repeated the assay using an HLA-E antigen, GFP+ and GFP- cells were eliminated at the same rate for all three viral reporter constructs. Conclusions: Our findings indicate that HIV-infection does not generally render CD4 T cells more resistant to CTL-mediated lysis. While some immune escape mechanisms, such as the downregulation of classical MHC class I molecules, can lower the antigen availability and therefore limit recognition by specific CTL clones, this does not affect their susceptibility to cell death. HIV-Specific T and Humoral Response: Data From the First Pediatric Combined Therapeutic Vaccine Trial Arianna Rotili 1 , Chiara Pighi 2 , Giulio Olivieri 2 , Alessia Neri 1 , Sarah Moreland 3 , Elena Morrocchi 1 , Ellen Turk 3 , Shaun Barnabas 4 , Mark Cotton 4 , Mark de Souza 5 , Hans Spiegel 6 , Nicola Cotugno 2 , Merlin Robb 7 , Paolo Palma 2 , for the HVRRICANE Study Group 1 University of Rome Tor Vergata, Rome, Italy, 2 Ospedale Pediatrico Bambino Gesu, Rome, Italy, 3 Walter Reed Army Institute of Research, Silver Spring, MD, USA, 4 Family Clinical Research Unit, Tygerberg, South Africa, 5 Institute of HIV Research and Innovation, Bangkok, Thailand, 6 National Institutes of Health, Bethesda, MD, USA, 7 United States Military HIV Research Program, Bethesda, MD, USA Background: Therapeutic vaccines offer a promising approach to decrease HIV reservoirs, enhance immunity and enable ART-free remission. This study characterizes HIV-specific T and humoral responses following prime-boost vaccination of the HVRRICANE trial: HIVIS DNA and MVA-CMDR vaccines ± the TLR4 agonist with Cervarix HPV vaccine co-administration. Methods: HVRRICANE enrolled 25 South African adolescents with perinatal HIV, virally suppressed (VL<200 copies/ml) on ART since 6 mo of age. The trial design is in Fig 1. Comprehensive evaluations included viral reservoirs and immunogenicity assements. HIV-specific T cells were longitudinally tested by IFN-γ/IL-2 Fluorospot assays, stimulating thawed PBMCs with GAG or ENV peptide pools. Activation Induced Molecules (AIM)/Intracellular Cytokine Staining (ICS) assays complemented these analyses, along with Western Blot (WB) serology for Abs against 10 HIV-1 antigens. Results: Overall, we observed a sustained rise in HIV-specific T cell responses following vaccination, which remained high over time. At wk60, IFN-γ, IL-2 and combined IFN-γ/IL-2 responses to GAG and ENV stimulation increased from baseline (wk0). Comparisons among all time points within arms showed that in Arm 2, IL-2, IFN-γ and poly-functional T cells increased during the vaccination in response to GAG (p=0.0486, p=0.0057, p=0.0477). Arm 2 also exhibited higher IFN-γ production response to ENV (p=0.0012). Comparisons at each time point between arms revealed significant differences in IFN-γ response to GAG and ENV at wk0 across all arms (p=0.0133, p=0.0297) and between Arms 2 and 3 (3 > 2, p=0.0321, p=0.0085). Differences in IL-2-producing T cells to ENV were noted between Arm 2 and 3 (3 > 2, p=0.0433). IFN-γ-producing T cells showed significant differences between Arms 1 and 2 (1 > 2, p=0.0091) after GAG stimulation. At wk40 (after normalizing for wk0) IFN-γ responses differed between Arms 1 and 2 (2 > 1) to both GAG (p=0.0452) and ENV (p=0.0312), with further differences at wk48 between Arms 2 and 3 to ENV (2 > 3, p=0.0321). Significant differences in WB score were noted among groups at wk0 (p=0.0352). Increases in both p24 (p=0.0156) and WB (p=0.0391) scores over time were found in Arm 1. No variation in single copy viral load was detected among and within Arms. Conclusions: Data show strong and lasting HIV-specific immunity from the vaccine regimens tested, paving the way for immunotherapy to reduce the viral reservoir in children and youths with HIV. HIV-1-Specific T Cells From Post-Treatment Controllers and Non Controllers Lisa L. Dietz 1 , Rikke Olesen 1 , Anna K. Juhl 1 , Jesper D. Gunst 2 , Miriam Rosás Umbert 3 , Ole Søgaard 1 1 Aarhus University, Aarhus, Denmark, 2 Aarhus University Hospital, Aarhus, Denmark, 3 Centre de Recherche du CHUM, Montreal, Canada Background: Understanding the immune response to HIV-1 in individuals maintaining long-term viral suppression after analytical treatment interruption (ATI) is crucial in the search for a functional cure. A subset of individuals, The figure, table, or graphic for this abstract has been removed.

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Poster Abstracts

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CROI 2025