CROI 2019 Abstract eBook

Abstract eBook

Poster Abstracts

POSTER ABSTRACTS

166 ENTRY KINETICS OF GLOBALLY REPRESENTATIVE AND VERTICALLY TRANSMITTED HIV ENVELOPES

Nicholas E. Webb , Nicole Tobin, Grace M. Aldrovandi University of California Los Angeles, Los Angeles, CA, USA

Background: Understanding HIV entry kinetics may reveal important dynamic properties relevant to transmission and vaccine design. To date, most entry kinetics studies are limited to either lab-adapted isolates or a limited selection of primary isolates and their mutational derivatives. We sought to determine the breadth of naturally occurring HIV-1 isolates. Methods: An optimized time-of-addition assay with T20 was used to measure the kinetics of the transition between the prehairpin (PHI) and 6-helix bundle (6HB) states of HIV gp41 for more than 150 primary envelopes (Env). Env isolates included a globally representative panel (global) and vertically transmitted Envs associated with in-utero (IUT, 5 mom/baby pairs, 37 Envs) and breast milk (BMT, 6 mom/baby pairs, 50 Envs) transmission. Normalized time- dependent infectivity data were fit to a lognormal cumulative distribution. The corresponding probability distribution (PDF) was used to derive the average time it takes to reach the PHI/6HB transition (delay, time point of greatest increase in infection) and the duration of transition (width of PDF at 75% of its maximum, in minutes). Results: Lognormal distributions fit the data with high accuracy (R 2 >0.85 for 99% of experiments). The delay and duration among global Envs ranged from 3-15 minutes and 6-35 minutes, respectively. IUT Maternal/infant isolates had a uniquely confined range of delay/duration with some of the fastest kinetics (~1 min). BMT Env kinetics were highly diverse and 3/6 infants each harbored a single Env with remarkably long delays of 40–60 minutes and equally long durations. Kinetic interpretations of these metrics were supported by strong correlations to both T20 (R 2 =0.87) and 10E8 sensitivity (R 2 =0.79) across a 1000 and 100-fold range of EC 50 , respectively. Conclusion: Circulating HIV Envs exhibited a broad range of PHI kinetics that reflect their diverse nature. PHI kinetics were also significant determinants of sensitivity to both T20 and 10E8, one of the broadest neutralizing antibodies known to date. Vertically transmitted BMT isolates exhibited remarkably unique kinetic extremes suggesting a functional bottleneck in this transmission route that restricts labile Envs, while IUT isolates were highly restrained in both delay and duration. The naturally occurring, kinetically slow Envs we identify may offer unique insights into the design of highly stable and native gp41 antigens that reflect the natural diversity of Env.

Poster Abstracts

167 CD4-DEPENDENT MODULATION OF HIV-1 ENTRY BY LY6E Jingyou Yu 1 , Chen Liang 2 , Shan-Lu Liu 1

1 The Ohio State University, Columbus, OH, USA, 2 McGill University, Montreal, QC, Canada Background: The role of IFN-induced genes (ISGs) in viral infection remains incompletely understood. While most ISGs are antiviral, some ISGs have been shown to promote viral infection, including HIV-1. Indeed, we previously showed that IFN-inducible LY6E protein promotes HIV-1 infection in human PMBCs and high CD4-expressing SupT1 cells. Methods: We examined the effect of LY6E on low- and high-CD4+ T cells, as well as human primary cells including monocyte-derived macrophages (MDMs). We used shRNAs to knock down the endogenous LY6E in these cells and determined its influence on HIV-1 entry and replication. We performed immunofluorescence microscope imaging analysis to examine the co- localization between CD4 and LY6E. We performed lipid flotation assay to dissect the biophysical and functional interplay between CD4 and LY6E on the plasma membrane and intracellular compartments. Results: We provide evidence that LY6E inhibits HIV-1 entry and spread in low CD4-expressing Jurkat cells and human monocyte-derived macrophages (MDMs), through downregulation of the viral receptor CD4 from the plasma membrane. We found that knockdown of LY6E in Jurkat cells increases HIV-1 entry yet overexpression of LY6E in Jurkat cells inhibits HIV-1 entry and replication. LY6E is co-localized with CD4 in Jurkat cells and MDMs and enhances the CD4 internalization from the plasma membrane. We artificially manipulated the CD4 level in Jurkat and SupT1 cells and found that overexpression of CD4 in Jurkat cells overcomes the inhibitory effect of LY6E; blocking the function of CD4 in SupT1 with a neutralizing antibody eliminates the enhancement of LY6E on HIV-1 entry. The CD4-dependent inhibitory phenotype of LY6E can be recapitulated in low CD4-expressing human MDMs. Conclusion: Our study reveals a CD4-dependent function of LY6E that distinctly modulates HIV-1 entry and replication. Given that HIV-1 targets low CD4- expressing cells during primary infection but replicates efficiently in high CD4-

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CROI 2019