CROI 2025 Abstract eBook

Abstract eBook

Poster Abstracts

539

Resistance of Inducible, Infectious HIV-1 to Autologous Neutralizing IgG After Long-Term ART Natalie F. McMyn 1 , Joseph Varriale 1 , Hanna Wu 1 , Vivek Hariharan 1 , Jun Lai 1 , Anushka Singhal 1 , Kenneth Lynn 2 , Karam Mounzer 3 , Pablo Tebas 2 , Luis J. Montaner 4 , Colin M. Kovacs 5 , Rebecca Hoh 6 , Steven G. Deeks 6 , Janet M. Siliciano 1 , Robert F. Siliciano 1 1 The Johns Hopkins University School of Medicine, Baltimore, MD, USA, 2 University of Pennsylvania, Philadelphia, PA, USA, 3 Philadelphia FIGHT, Philadelphia, PA, USA, 4 The Wistar Institute, Philadelphia, PA, USA, 5 University of Toronto, Toronto, Canada, 6 University of California San Francisco, San Francisco, CA, USA Background: The major barrier to HIV-1 cure is a small, stable pool of latently infected resting CD4+ T cells. Following cessation of antiretroviral therapy (ART), there is rapid, exponential viral rebound from this latent reservoir. Cure strategies aim to prevent viral rebound. Autologous neutralizing antibodies (aNAbs) have been shown to block outgrowth of a substantial but variable fraction of viruses in the latent reservoir of people with HIV (PWH). However, it is not known whether aNAbs can neutralize viruses persisting after long-term ART (>20 years). Methods: We conducted TZM-bl neutralization assays with HIV-1 env pseudoviruses of inducible, replication-competent outgrowth viruses from 15 PWH on long-term ART (>14 years, mean 22 years). For comparison, we analyzed outgrowth viruses isolated from 12 PWH on intermediate ART (mean 7 years). Neutralization assays tested either contemporaneous aNAbs or one of three broadly neutralizing antibodies (bNAbs; VRC01, 10-1074, PGDM1400). To address waning antibody levels, neutralization assays were conducted with a tier 1 virus (SF162), and longitudinal IgG samples from study participants. In addition, antibody-dependent cellular cytotoxicity (ADCC) assays were performed with NK cells, participant pseudoviruses, and contemporaneous IgG. Results: Most replication-competent viral isolates (76%) from PWH on long term ART were resistant to neutralization by aNAb with IC 50 values >100 ug/ml. The fraction of resistant isolates was significantly higher than that observed for PWH on intermediate ART (38%, p = <0.0001). In contrast, outgrowth viruses from both groups remained sensitive to bNAbs (median bNAb IC 50 : 0.9 to 1.5 ug/ ml). Autologous IgG from 94% of long-term ART participants neutralized SF162 virus, indicating long-term persistence of neutralizing antibody responses. Longitudinal analysis revealed aNAb maturation, stability, and waning over long-term ART in different participants. We also observed ADCC activity in antibodies from PWH on long-term ART. Conclusions: Our findings demonstrated increased resistance of outgrowth viruses to aNAbs over long-term ART, which was not fully explained by a decline in neutralizing antibody concentrations. This increased resistance may be driven partially by ADCC-mediated elimination of infected cells carrying aNAb-sensitive viruses, leaving only aNAb-resistant viruses which can contribute to viral rebound. High Networked CD8+ T-Cell Epitopes Exhibit Markedly Reduced Mutability in the Latent HIV Reservoir Fernando Senjobe 1 , Itai Muzhing 2 , Jonathan Urbach 2 , Anusha Nathan 2 , Rhoda Tano-Menka 2 , Clarety Kaseke 2 , Gaurav D. Gaiha 2 1 Harvard University, Cambridge, MA, USA, 2 Ragon Institute of MGH, MIT and Harvard, Cambridge, MA, USA Background: The persistent HIV latent reservoir is a major impediment to the eradication of HIV infection for people living with HIV (PLWH). CD8+ T cell-based approaches to control viral rebound have in part been unsuccessful due to the emergence of epitope escape mutations. Our laboratory identified a subset of epitopes, known as highly networked CD8+ T cell epitopes, that are constrained from mutation and are preferentially targeted by individuals who spontaneously control HIV. In this study, we assessed whether highly networked epitopes represent a set of mutationally constrained targets in the latent HIV reservoir for durable HIV suppression. Methods: To determine mutational frequencies of highly networked and non-networked epitopes in the latent reservoir, we performed proviral and near full-length individual proviral (FLIP) sequencing on genomic DNA obtained from sorted latently infected CD4+ T cells derived from 22 PLWH on suppressive ART. Participants also maintained undetectable viral loads at the time of sample collection. Mutational sequence analysis of viral epitopes was performed using an established computational pipeline to quantify the quantity and quality of viral mutations. We subsequently investigated the extent to which CTLs can

cross-recognize wild type (WT) and mutant (mt) networked and non-networked epitopes using cross-reactivity assays. Results: Sequences analyses revealed that highly networked epitopes overall had a markedly reduced frequency of mutations than non-networked epitopes in integrated proviruses (P<0.0001), and when the analysis was limited to epitopes restricted by individual HLA class I haplotypes (P<0.0002). Moreover, non-networked epitopes exhibited a marked enrichment for either multiple mutations (>1) or non-conservative mutations. In addition, T cell responses to highly networked epitopes demonstrated preserved recognition of mutated epitopes from proviral sequences, whereas mutated non-networked epitopes had significantly reduced recognition. Conclusions: These data demonstrate that highly networked epitopes have markedly fewer overall and non-conservative mutations in the latent reservoir from ART-suppressed PLWH. CD8+ T cells recognize mutants of high networked epitopes better than mutants of non-networked epitopes. These findings therefore suggest that highly networked epitopes represent a set of mutationally constrained targets for therapeutic T cell vaccine development that may enable durable viral suppression following ART cessation. Autologous IgGs Mediate Log Reductions in HIV Infection in a PTC, Contributing to ART-Free Remission Junlin Zhuo 1 , Mauro Garcia 1 , Jesper D. Gunst 2 , Katarzyna Janowska 3 , Muralikrishna Lella 3 , Xiao Huang 3 , Donald Lubbeck 4 , Cayla Wilson 3 , Christy L. Lavine 5 , Michael S. Seaman 5 , Derek W. Cain 3 , Priyamvada Acharya 3 , Ole Søgaard 6 , Janet M. Siliciano 1 , Robert F. Siliciano 1 1 The Johns Hopkins University School of Medicine, Baltimore, MD, USA, 2 Aarhus University Hospital, Aarhus, Denmark, 3 Duke Human Vaccine Institute, Durham, NC, USA, 4 The Johns Hopkins University, Baltimore, MD, USA, 5 Beth Israel Deaconess Medical Center, Boston, MA, USA, 6 Aarhus University, Aarhus, Denmark Background: In people living with HIV on suppressive ART, the latent reservoir is composed of archived viral variants that are either sensitive or resistant to autologous neutralizing antibodies (aNAbs), with the latter capable of causing rebound following treatment interruption. We hypothesized ART-free virologic control might be achieved if aNAbs developed to neutralize all inducible, replication-competent reservoir variants. Study participant ID107 enrolled in the eCLEAR trial received broadly neutralizing antibody 3BNC117 and latency reversing agent romidepsin shortly after ART initiation, which was 2 months after HIV acquisition. He underwent an analytical treatment interruption 400 days after ART initiation and has maintained ART-free HIV remission for >6 years despite lacking protective HLA alleles. We characterized the aNAb response for this participant. Methods: Quantitative viral outgrowth assays (QVOA) were conducted to obtain inducible, replication-competent reservoir viruses. Env sequences from outgrowth viruses were tested for sensitivity to aNAbs in pseudovirus neutralization assays with IgGs isolated from plasma collected at 12 longitudinal timepoints. Partial env sequences [HXB2: 827-1835] were obtained from plasma collected 5.4 years off ART. Soluble, stabilized Env trimers resembling autologous Env were purified for biochemical and structural analysis. Results: The frequency of CD4 + T cells with inducible, replication-competent virus was 0.34 infectious units per million (IUPM), consistent with previous IUPM values obtained during ATI. Residual viremia env sequences were identical to most of the pre-ART viruses and many outgrowth viruses identified during the study. aNAbs from 11 timepoints readily neutralized autologous pseudoviruses (IC 50 0.39- 5.2 μg/mL) but not heterologous viruses. To further characterize the aNAb responses, we calculated the instantaneous inhibitory potential (IIP), a measure of the number of logs of single round infection events inhibited at a given therapeutic dose. At average human serum IgG concentration (10 mg/mL), this participant’s aNAbs mediated a 5-7 log reduction in new infection events, comparable to many ART regimens. A 5.6 Å cryoEM structure of unliganded ID107 Env was obtained. Conclusions: This participant has maintained ART-free remission for >6 years despite a reservoir size in the normal range. The aNAb responses that developed may contribute to the prolonged ART-free remission of study participant ID107.

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Poster Abstracts

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CROI 2025 141