CROI 2025 Abstract eBook

Abstract eBook

Poster Abstracts

blockade and Ornithine consistently and significantly reduced proportions of autologous HIV-1 infected cells in vitro (p=0.0156). Conclusions: Modulation of lipid and aminoacid metabolism may represent a promising strategy to restore dysfunctional HIV-specific TIGIT+CD8+T cells in PWH.

cells were labeled with fluorescently tagged HLA-peptide tetramers presenting immunodominant epitopes of the HIV proteome (Figure 1) and stimulated with soluble peptides. The expression of surface proteins and cytokines in response to peptide stimulation was monitored by flow cytometry. Results: We observed comparable frequencies of cells recognizing immunodominant epitopes of the HIV proteome among the CD4 and CD8 T subsets. Their functional profiles, however, differed significantly even when targeting the same protein with CD4 T cells being less responsive to stimulation (p<0.0001) and expressing high levels of CXCR5 (p<0.001), CD40L (p<0.05), and IL-4/-13 (p<0.0001) while CD8 T cells expressed higher levels of PD-1 (p<0.001), CD107a (p<0.0001), IFN-γ (p<0.0001) and IL-2 (p<0.001). Intriguingly, protein specificity played an important role in the case of CD4 T cells where cells targeting epitopes within the p24 protein showed increased PD-1 expression (p<0.01), cytotoxicity (p<0.001), and responsiveness to stimulation (p<0.01) while cells specific for the gp120 showed increased CXCR5 (p<0.0001) expression. In comparison to CD8 T cells, more CD4 T cell functions were associated with viral load and IFN-γ-expression was inversely correlated with the viral load for both subsets (r=-0.49, p<0.001 for CD4 and r=-0.54, p<0.01 for CD8 T cells). No dependence on the protein specificity was observed when correlating different functions of the tetramer-specific CD4 and CD8 T cells. Conclusions: Taken together our findings demonstrate distinct functional profiles of CD4 and CD8 T cells targeting the same HIV protein and stronger dependence of CD4 T cells on viremia and protein specificity. The interplay between the CD4 and CD8 T cells was not dependent on protein co-targeting. Provirus From Early-Treated HIV Reveals Earlier Variants Targeted by Initial Neutralizing Antibodies Hunter M. Courtney 1 , Gregory D. Whitehill 1 , Ryan Krause 1 , Noah Beratan 1 , Sita Kottilil 1 , Francesco E. Marino 1 , Suvadip Mallick 1 , Rebecca Hoh 2 , Heather Hartig 2 , Vivian Pae 2 , Sannidhi Sarvadhavabhatla 2 , Maria Sophia Donaire 2 , Steven G. Deeks 2 , Sulggi Lee 2 , Katharine Bar 1 1 University of Pennsylvania, Philadelphia, PA, USA, 2 University of California San Francisco, San Francisco, CA, USA Background: Antiretroviral therapy initiation (ARTi) halts HIV-1 replication but cannot clear persistent reservoirs. ARTi during acute (within 60 days of acquisition) and early (between ~60 and 120 days) HIV-1 limits reservoir size and diversity and can preserve nascent autologous neutralizing antibody (anAb) responses that target the transmitted/founder (TF) virus and then gain potency and breadth over viral suppression to target later variants. In a cohort of acute and early ART-treated people with HIV-1 (PWH), we compared viral sequences and anAb sensitivities of plasma and reservoir viruses. Methods: Within a subset of the UCSF Treat Acute cohort (n=7 PWH [2 acute-, 5 early-treated; 7 male, 0 female]; NCT02656511), single genome sequencing (SGS) of gp160 env from plasma at ARTi and PBMC provirus from 24 weeks of ART was performed; sequences were analyzed by maximum-likelihood amino acid phylogenetic trees on a per-participant basis. Select Envs were tested for neutralization sensitivity to longitudinal plasma IgG by TZM.bl assays. Chimeric Envs encoding select regions were generated to map anAb responses at the molecular level. Results: 221 SGS-derived envs were sampled ( n =134 plasma, n =87 proviral) across the 7 participants. Phylogenetic analyses of acute-treated participants showed co-alignment of plasma and reservoir sequences. In early-treated participants, however, proviral env persisting at 24 weeks of ART were generally enriched at tree roots while plasma env from the time of ARTi were biased toward branch tips. In some participants, reservoir envs revealed large branches no longer sampled in the plasma. Thus, reservoir env allowed inference of earlier variants no longer or less frequently replicating at the time of ARTi. In a subset of early-treated participants, plasma IgG from the time of ARTi potently neutralized archived reservoir Envs while plasma variants were resistant; IgG from later timepoints neutralized both reservoir and plasma Envs. Using

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Unmodified mRNA Compared to Modified mRNA Induces Optimal CD8+ T-Cell Responses in Rhesus Macaques Sampa Santra 1 , Michelle Lifton 1 , Benjamin J. Mildenberg 1 , Georgeanna M. Morton 1 , Han Tran 1 , Laura L. Sutherland 2 , Robert Parks 2 , Bette T. Korber 3 , Tomas Hanke 4 , Persephone Borrow 5 , Drew Weissman 6 , Francois Villinger 7 , Barton Haynes 2 1 Beth Israel Deaconess Medical Center, Boston, MA, USA, 2 Duke Human Vaccine Institute, Durham, NC, USA, 3 Los Alamos National Laboratory, Los Alamos, NM, USA, 4 The Jenner Institute, Oxford, UK, 5 University of Oxford, Oxford, UK, 6 University of Pennsylvania, Philadelphia, PA, USA, 7 University of Louisiana at Lafayette, Lafayette, LA, USA Background: CD8+ T cells play a pivotal role in controlling replication of HIV-1/ SIV in vivo . Vaccine-elicited CD8+ T cell responses have been associated with reduced peak viremia and viral set points. Nucleoside-modified mRNA ionizable lipid nanoparticle (LNP) vaccines have been shown to induce particularly strong CD4+ T follicular helper cell and neutralizing antibody responses, whereas unmodified mRNA vaccines induce higher CD8+ T cell responses. In the present study, we compared the induction of CD8+ T cell responses in rhesus monkeys immunized with different ratios of unmodified vs modified mRNA-LNPs encoding a T cell immunogen, SIVconsv239, SIV 239 analog of the most conserved regions of HIV proteome. Methods: We immunized four groups of NHPs (n=5/group) intramuscularly with 50mg of mRNA-SIVconsv239 in LNPs on weeks 0, 4 and 8 as follows: 100% 1-methylpseudouridine modified mRNA (Group 1), 70% modified mRNA with 30% unmodified mRNA (Group 2), 30% modified mRNA with 70% unmodified mRNA (Group 3) and 100% unmodified mRNA (Group 4). Monkeys in Group 5 received ChAdOx1.SIVconsv239 at weeks 0 and 4 as a positive control. We analyzed CD8+ T cell responses by SIV gag p11C tetramer staining of whole blood of Mamu-A*01 + monkeys, and tested PBMC in ELISpot and intracellular cytokine assays using an immunogen-specific peptide pool (M3). Results: On week 12 of the study, unmodified mRNA (group 4) elicited 24.7-fold higher tetramer-reactive CD8 + T cell responses than 100% modified mRNA (group 1). M3-specific IFN-g ELISpot responses were also significantly higher in group 4 than in group 1 (p=0.003; Unpaired t-test). ELISpot responses were comparable in groups 4 and 5 (p=0.66; Unpaired t-test). ICS assays performed at week 12, showed for IFN-g both CD4+ and CD8+ responses were significantly higher in group 4 than in group 1. Notably, IFN-g ELISpot assay performed 22 weeks after the last immunization showed that unmodified mRNA immunizations elicited more durable M3-specific T-cell responses than either modified mRNA or ChAdOx1. Conclusions: Immunization with unmodified mRNA elicited higher magnitude CD8 + T cell responses than modified mRNA, which were comparable to responses induced by viral vector ChAdOx1. Moreover, unmodified mRNA immunizations elicited more durable T-cell responses than ChAdOx1. Thus, to induce both CD8+ T cell and neutralizing antibody responses, addition of unmodified mRNA to modified mRNA immunogens may be required. The Impact of Protein Specificity on Function and Crosstalk Between the HIV-Specific T Cells Jernej Pusnik 1 , Falko Heinemann 2 , Andreas Heinold 2 , Enrico Richter 1 , Stefan Esser 3 , Heiko Jessen 4 , Julie Ake 5 , Trevor Crowell 5 , Merlin Robb 5 , Hendrik Streeck 1 1 Bonn University Hospital, Bonn, Germany, 2 University Hospital of Duisburg-Essen, Essen, Germany, 3 University Hospital Essen, Essen, Germany, 4 Praxis Jessen ² + Kollegen, Berlin, Germany, 5 US Military HIV Research Program, Bethesda, MD, USA Background: HIV-specific CD8 T cells can control HIV replication but become increasingly exhausted and dysfunctional with progressing disease. It has been previously shown that this is caused by a lack of CD4 T cell help in addition to persistent antigenemia. However, the interplay between T cells and their functions and the role of protein specificity in the crosstalk between CD4 and CD8 T subsets during chronic HIV infection has not been investigated. Methods: To determine the function of HIV-specific CD4 and CD8 T cell responses targeting different proteins we collected peripheral blood samples of 27 untreated individuals with HIV. Isolated peripheral blood mononuclear

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CROI 2025