CROI 2018 Abstract eBook

Abstract eBook

Poster Abstracts

292 HIV RECEPTOR USAGE IMPACTS SENSITIVITY TO V1-V3 LOOP BROADLY NEUTRALIZING ANTIBODIES Ludy Registre 1 , Yvetane Moreau 2 , Sila Ataca 1 , Manish Sagar 2 1 Boston University, Boston, MA, USA, 2 Boston Medical Center, Boston, MA, USA Background: Broadly neutralizing antibodies (bnAbs) are being investigated as a potential therapeutic. BnAbs target a relatively limited number of conserved HIV-1 envelope glycoprotein (env) structures, including glycans in and around the variable loop 1 – 2 (V1/V2) and 3 (V3) domains. Changes in the env V1/V2 and V3 loops are also known to dictate the use of either the CCR5 or CXCR4 chemokine receptor for cell entry. Methods: Full length envs (n =47) were isolated using single genome amplification and incorporated into isogenic backbones to construct replication competent viruses, which were then phenotypically characterized for coreceptor usage. Neutralization sensitivity of CCR5- and CXCR4- utilizing viruses was examined using the TZM-bl assay. Robetta online server, Pcons metaserver, and Pymol software was used for structural modeling studies of the interaction between HIV-1 env and bnAbs. Chimeric envs were generated to validate the structural modeling predictions. Results: Viruses that exclusively use CXCR4 (X4) from 8 individuals as compared to variants that only use CCR5 (R5) from 9 subjects were around 5 fold less sensitive to anti-V3 antibodies PGT121 (p=0.02) and 10-1074 (p=0.04). X4-using viruses were less neutralization sensitive to V1/V2 loop directed antibodies, PG9 and PG16, as compared to R5-using viruses, although this difference was not statistically significant. Multiple co-circulating X4 (median=4, range=1-5) as compared to R5 envs (5 per subject) isolated from 4 subjects also demonstrated decreased sensitivity to V1-V2 and V3 directed bnAbs although these differences were subject specific. Both intra and inter individual R5 and X4 variants did not have significant neutralization susceptibility differences to CD4 binding site (VRC01) and membrane proximal external region (10E8) directed bnAbs. Structural modeling suggested that the envs with resistance to V3 directed bnAbs had V1/V2 loops that sterically interfered with antibody binding to known PGT121 and 10-1074 epitope. PGT121 susceptibility increased when the V1/V2 loop of an env insensitive to PGT121 was replaced with the V1/V2 loop from an env sensitive to PGT121 and vice versa. Conclusion: Neutralization susceptibility to V1-V2 and V3-directed bnAbs associates with coreceptor usage. Structural modeling predicts that V1-V2 loop mediated steric hindrance prevents V3-directed bnAb – env interactions. Our structural modeling techniques may be used as a tool to predict neutralization susceptibility to bnAb based therapies. 293 USE OF PROMISCUOUS GLYCAN AT V3 REGION CORRELATES WITH ELITE NEUTRALIZATION RESPONSE Nandagopal Paneerselvam 1 , Jayantha Bhattacharya 2 , Aylur K. Srikrishnan 1 , Rajat Goyal 3 , Chinnambedu Ravichandran Swathirajan 1 , Shilpa Patil 2 , Shanmugam Saravanan 1 , Suprit Deshpande 2 , R Vignesh 1 , Sunil S. Solomon 4 , Nikhil Singla 3 , Joyeeta Mukherjee 3 , Kailapuri G. Murugavel 1 1 YR Gaitonde Center for AIDS Research and Education, Chennai, India, 2 HIV Vaccine Translational Research Laboratory, Faridabad, India, 3 International AIDS Vaccine Initiative, New York, NY, USA, 4 Johns Hopkins Hospital, Baltimore, MD, USA Background: Broadly neutralizing antibodies to HIV provide important leads for vaccine design and may be valuable in therapy. Defining the sites of vulnerability can inform the choice of immunogens and immunization strategies to induce broadly neutralizing antibodies through vaccination. Here we report on the epitope specificity of elite neutralizers with subtype C infected individuals in India Methods: In this study, plasma samples from a cohort of 70 ART-Naïve HIV- infected individuals with various stages of disease progression were tested against Tier-2 global virus panel (n=11) which includes subtype A, B, C, G, AC, BC & AE. Subjects with < 50 % neutralization breadth were defined as non- broadly cross-reactive neutralization group (Non-BCN) and those with >50 % neutralization breadth was defined as the broadly cross-reactive neutralization group (BCN) were then tested against an extended virus panel (n=19) to find Elite neutralization. Elite neutralizers are those able to neutralize >70% of viruses tested with geometric mean ID50> 500.Comprehensive neutralization, binding and competition analysis were performed to map the epitope of elite neutralizers. Results: Out of 70 samples screened, 28 (40%) of them neutralized >50% of the global virus panel and 8(11%) of these plasma have broad and potent

antibody response when tested with extended virus panel.we were able to identify 4 elite neutralizers with geometric mean ID50 titer between 500 and 700. Epitope mapping of those elite neutralizers were not specific to known targets like V2, V3, CD4bs and MPER region. Interestingly, two of the elite neutralizers (Figure.1; LT-VNP04;p=0.010 &TP-14, p=0.013) show enhanced significant sensitivity towards viruses that lacks N332 glycan. In addition to that, rest of the elite neutralizers (Figure.1; LT-VNP03;p=0.54 & LT-VNP20,p=0.10) does not depend on either presence or absence of N332 glycan. Conclusion: Elite neutralization response was associated with the absence of N332 glycan. This may be due to utilization of promiscuous glycan at the high mannose patch of V3 region that favours the development of neutralization breadth among elite neutralizers. These data suggest promiscuous glycan are the potential target region for the development of immunogen that elict broad and potent antibody response.

Poster Abstracts

294 ENV STRUCTURE IS EVOLVING AT DIFFERENT RATES IN DIVERSE CLADES OF HIV-1 Raghavendranath Kandula, Hagit Hodis, Yunxia O’Malley, Kallin Khan, Hillel Haim University of Iowa, Iowa City, IA, USA Background: The Envelope glycoproteins (Envs) of viruses from diverse HIV-1 clades show different patterns of recognition by broadly neutralizing antibodies (BNAbs). We recently analyzed BNAb binding patterns of clade B Envs circulating in a defined region in the United States and observed significant changes during the past 30 years (DeLeon, Hodis, O’Malley et al., PLOS Biology 2017). BNAb epitopes are present in a decreasing proportion of circulating strains. The population decay rate of each epitope is distinct and remained constant over the course of the pandemic. Interestingly, epitopes that show higher rates of historic decay also exhibit higher rates of in-host divergence and higher levels of variance among strains that co-circulate in the individual at any time point (a parameter we designate volatility). We sought to compare the decay rates of epitopes in different HIV-1 clades and the relationship with their volatilities. Methods: To calculate BNAbs epitope integrity based on sequence, we utilized sequence-phenotype datasets to learn the relative contribution of each residue and position that composes an epitope to antibody binding. These values were then applied to large historic sequence datasets from clades B, C, D and CRF01_AE to determine changes in epitope integrity. Measured decay rates were compared with the mean volatility of the epitope in patients infected by virus from the same clade. Results: Many BNAb epitopes demonstrated different decay rates in the above clades. Domains that showed major differences include the glycan patch of gp120, the MPER of gp41 and quaternary structure-dependent epitopes.

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