CROI 2025 Abstract eBook

Abstract eBook

Poster Abstracts

capacity of Abs in these B cell subsets to develop polyfunctional antiviral activities. Public Trimer-Specific IgHV4-34 Clonotype in bNAb Inducers Includes a Novel V3-Glycan bNAb Subclass Daniel Schmidt 1 , Merle M. Schanz 1 , Lisanne L. Hubregtse 1 , Borys Pedenko 2 , Piotr Szwedziak 1 , Nikolas Friedrich 1 , Chloé Pasin 1 , Cyrille Niklaus 1 , Winfried Weissenhorn 2 , Penny L. Moore 3 , Huldrych F. Günthard 1 , Roger D. Kouyos 1 , Peter Rusert 1 , Alexandra Trkola 1 , for the Swiss HIV Cohort Study 1 University of Zurich, Zurich, Switzerland, 2 Université Grenoble Alpes, Grenoble, France, 3 National Institute for Communicable Diseases, Johannesburg, South Africa Background: Several classes of HIV-1 broadly neutralizing antibodies (bnAbs) exhibit distinct immunoglobulin heavy chain variable (IGHV) gene usage, and many HIV vaccine strategies aim to elicit public bnAb clonotypes. Here, we performed a systematic analysis of HIV-1 envelope (Env) trimer reactive B cell receptor (BCR) repertoires in bnAb inducers to define public features of IGHV and IGLV/KV gene segment usage, enabling the discovery of novel bnAbs. Methods: bnAb inducers (N=36) included in the XbnAb cohort (Pasin et al. biorXiv 2024) were analyzed by single cell BCR cloning (10X genomics with Libra Seq) to identify Env-trimer reactive BCRs. Neutralization activity was measured against a 41-virus multi-clade Env pseudotype panel. bnAb epitopes were defined by Env mutant screens (mutational scanning, binding, neutralization) and Cryo-EM structure analysis. Results: BCR repertoire analysis of 36 bnAb inducers identified a total of 1,218 individual IgG and IgA trimer-reactive BCRs assigned to 869 BCR lineages. IG gene segment usage was generally comparable between trimer-reactive and non-trimer BCRs. IGHV4-34/IGKV2-24 was rare in non-trimer (0.06% total Ig, 0.07%, IgA) but remarkably enriched in trimer-reactive BCR families (4.26% total Ig, 9.84% IgA). We identified IGHV4-34 bnAbs SHCS-0209 (IGKV2-24), SHCS-3L6 (IGKV2-24) and SHCS-3D14 (IGKV3-15) with 63%, 78%, and 88% breadth, respectively. IGHV4-34 usage is known to be associated with autoreactivity, and the autoreactive IGHV4-34 codon 26 was retained in SHCS-3L6 and SHCS-3D14 but mutated in SHCS-0209. Trimer-reactive IGHV4-34 BCRs were found in 30/36 bnAb inducers, and those with similarity to SHCS-3L6 (short CDR-H3/ IGKV2-24 usage) in 12/36 donors, suggesting the existence of IGHV4-34 public clonotypes. Cryo-EM structure analysis showed that SHCS-0209 has a clear silent face specificity. However, SHCS-3L6 targets V3-glycans (N301, N332) as well as glycans in the silent face (N262, N295). SHCS-3D14 targets the V3 (N301), V2-loop and CD4bs of the adjacent protomer. Neutralization correlation analyses with reference bnAbs and bnAb inducer plasmas (N=304) showed that SHCS-3L6 and SHCS-3D14 cluster distinctly from V3-glycan and silent face bnAbs, forming a novel subclass we termed V3-glycan type II. Conclusions: The high frequency of trimer-reactive IGHV4-34 BCRs, and the identification of novel IGHV4-34 bnAbs suggests that, provided the autoreactivity associated with IGHV4-34 could be mitigated, targeting IGHV4-34 for bnAb vaccines could be valuable.

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In Nonsuppressible Viremia, HIV Env Can Maintain Resistance to Autologous Neutralizing Antibodies Sang Hyeon Kim 1 , Behzad Etemad 1 , Ashley Roche 1 , Abbas Mohammadi 2 , Christy L. Lavine 3 , Prerana Shrestha 1 , Michael M. Lederman 4 , Sigal Yawetz 1 , Scott Sieg 4 , Athe Tsibris 1 , Steven G. Deeks 5 , Jose Castillo-Mancilla 6 , Peter Anderson 7 , Michael S. Seaman 3 , Jonathan Li 1 1 Brigham and Women's Hospital, Boston, MA, USA, 2 The Valley Health System, Las Vegas, NV, USA, 3 Beth Israel Deaconess Medical Center, Boston, MA, USA, 4 Case Western Reserve University, Cleveland, OH, USA, 5 University of California San Francisco, San Francisco, CA, USA, 6 ViiV Healthcare, Brentford, UK, 7 University of Colorado Anschutz Medical Campus, Aurora, CO, USA Background: Nonsuppressible viremia (NSV) represent a subset of individuals with persistent low-level viremia due to a hyperactive HIV reservoir. Little is known about whether persistent antigenemia during NSV can induce a stronger immune response. Autologous neutralizing antibodies (aNAb) represent a key adaptive immune response for viral control and HIV rebound during treatment interruption has been linked to aNAb escape. We performed extended range plasma HIV RNA and near-full length (NFL) proviral sequencing at longitudinal timepoints from two participants with NSV. We evaluated the aNAb sensitivities of HIV env from both the plasma HIV (i.e., from producer proviruses) and intact proviruses that did not match any plasma sequences (i.e., non-producer proviruses). Methods: We performed an in-house assay for the extended range single genome amplification ( pol-env ) of low-level plasma viremia and NFL single genome sequencing (SGS) to identify both producer and nonproducer proviruses from multiple timepoints. We then cloned the HIV-1 env using ABC cloning to create pseudoviruses. aNAb neutralization of plasma RNA and nonproducer proviral env were evaluated using purified IgG from plasma samples collected at longitudinal timepoints. Serial dilutions of IgG that neutralized 50% of viral infection (IC50) was determined. Results: We compared the aNAb response for two NSV participants, LV8 and LV9, who demonstrated NSV with detectable viral loads of between 34-578 HIV-1 RNA copies/mL over 12 years for LV8 and 39-1270 copies/mL over 13 years for LV9. We evaluated aNAb activity in LV8 at 6 time points over 2 years and for LV9 at 5 timepoints over 3 years. Plasma env from both participants demonstrated relatively high levels of aNAb resistance over the entire period with IC50 of >101 ug/mL for LV8 and 57.5-94.9 ug/mL for LV9. This is despite no changes in LV8 plasma RNA env sequences over 2 years. HIV Env from non producer proviruses demonstrated a range of resistance to aNAb activity. Conclusions: During nonsuppressible viremia, plasma virus can show sustained resistance to aNAb activity over several years despite no changes in the plasma HIV env sequence. The underlying proviral reservoir demonstrated a wider range of aNAb sensitivity. Additional studies are needed to explore why detectable viremia may not stimulate a robust HIV-specific humoral response during ART.

Poster Abstracts

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CROI 2025