CROI 2019 Abstract eBook

Abstract eBook

Poster Abstracts

Results: We computationally validated that our method of lineage reconstruction was more accurate than maximum likelihood at identifying ancestral sequences for simulated antibody lineages similar to BF520.1. Our inferred naïve precursor bound HIV Env with a KD of 46μM. A bnAb evolved within six months of infection and required only 3% somatic hypermutation. Kappa chain substitutions were critical for bnAb functionality, validated by the observation of extensive contacts between the CDRL1 loop and the N332 glycan in our 4.8Å cryo-EMmap. For the heavy chain, CDRH1 and CDRH2 mutations were important for developing breadth and potency. Conclusion: Overall, the developmental pathway of this infant antibody includes features distinct from adult antibodies, including several that may be amenable to better vaccine responses. Our analysis highlights the importance of considering both the heavy and light chain in the development of HIV-specific bnAbs and the fact that light chain specificity can potentially be harnessed to develop vaccine approaches that elicit such bnAbs with relatively little mutation. 312 PROFILING ANTIBODY CROSS-REACTIVITY AMONG SIV ISOLATES USING A PEPTIDE MICROARRAY Anna S. Heffron 1 , David Baker 1 , Adam Bailey 2 , Eric Peterson 3 , Amelia K. Haj 1 , Mariel S. Mohns 1 , Connor Buechler 1 , Adam Ericsen 4 , Dawn M. Dudley 1 , John C. Tan 5 , David H. O’Connor 1 1 University of Wisconsin–Madison, Madison, WI, USA, 2 Washington University in St Louis, St Louis, MO, USA, 3 Wisconsin National Primate Research Center, Madison, WI, USA, 4 Yerkes National Primate Research Center, Atlanta, GA, USA, 5 Roche Sequencing Solutions, Madison, WI, USA Background: In the past decade, a number of broadly neutralizing human immunodeficiency virus (HIV) antibodies have been identified; however, tools for assessing antibody cross-reactivity are still relatively low throughput. Ultradense linear peptide arrays enable the determination of antibody reactivity to as many as six million peptides in a single assay. Identification of antibodies capable of binding a wide variety of HIV strains has potential to help guide the development of vaccines and therapeutics. Here we prototyped the use of an ultradense peptide microarray to assess antibody cross-reactivity from cynomolgus macaques infected with SIVmac239 against a panel of simian immunodeficiency virus (SIV) species used to infect macaques. Methods: Proteins represented on the array included the complete Env proteins of 21 strains of SIV and the complete proteome of SIVmac239, tiled in peptides 16 amino acids in length which overlapped by 12 amino acids. We assessed serum and plasma samples taken prior to infection and 125 days to 1 year after infection with SIVmac239 and compared pre-infection and post-infection antibody binding to proteins represented on the array. Fluorescence intensity from the application of a secondary antibody indicated regions in which primary antibodies had bound peptides representing the SIV proteins. Results: No or minimal binding against SIV viral peptides was observed prior to infection. Following infection, evidence of antibody binding was consistently observed in peptides representing the Gag, Pol, and Env proteins of SIVmac239, with the highest levels of binding in Env. Antibody binding against other SIVmac239 proteins was also observed, though these results were less consistent between animals. We observed variable levels of antibody binding to peptides from other SIV strains, though all animals assessed showed some degree of cross-reactive binding to some number of SIV strains other than the infecting strain. Conclusion: Serum profiling of antibody binding throughout the proteome of SIVmac239 and throughout the the Env proteins of multiple strains of SIV reveals cross-reactive antibody binding and highlights the potential of ultradense peptide arrays for high-throughput assessment of antibody binding specificity to diverse viruses. 313 REGULATION OF HIV-SPECIFIC CD8+ T-CELL FUNCTIONAL CAPACITY Rachel L. Rutishauser 1 , Christian Deo T. Deguit 1 , Hossam Abdelsamed 2 , Ashish Sharma 3 , Susan P. Ribeiro 3 , Rebecca Hoh 1 , Melissa Krone 1 , Frederick M. Hecht 1 , Christopher D. Pilcher 1 , Jeffrey N. Martin 1 , Benjamin A. Youngblood 2 , Rafick- Pierre Sekaly 3 , Steven G. Deeks 1 , Joseph M. McCune 1 , Peter W. Hunt 1 1 University of California San Francisco, San Francisco, CA, USA, 2 St. Jude Children’s Research Hospital, Memphis, TN, USA, 3 Case Western Reserve University, Cleveland, OH, USA Background: Many HIV cure strategies propose to elicit HIV-specific CD8+ T cell responses to control and/or eradicate the virus. We previously reported that

the T cell memory- and stem cell-associated Wnt signaling transcription factor, TCF-1, is expressed at significantly higher levels in HIV-specific CD8+ T cells from individuals who naturally control HIV infection. Moreover, its expression correlates with the proliferative capacity of these cells. Here, we explored the relationship between HIV-specific CD8+ T cell functional capacity and other molecular pathways associated with CD8+ T cell memory. Methods: HIV-specific CD8+ T cells were identified in the peripheral blood from Viremic (VL>8,000 copies/mL; n=14), ART-suppressed (VL<40 copies/ mL on stable ART for a median of 2 years; n=10), and Controller (VL<40 copies/ mL not on ART; n=12) HIV-infected individuals by staining with MHC Class I multimers. The expression of transcription factors, effector molecules, and surface proteins was measured in multimer+ CD8+ T cells and proliferation was evaluated after 6-day in vitro peptide stimulation. Whole-genome RNA sequencing and DNA methylation analysis were performed on sorted multimer+ cells from a subset of participants. Results: In addition to mounting greater proliferative responses and expressing higher levels of TCF-1 in all memory T cell subsets, multimer+ HIV-specific CD8+ T cells from Controllers (compared to Viremic or ART-suppressed individuals) were more likely to express CD127 and less likely to express PD-1, Granzyme B, and Tbet. Unstimulated multimer+ cells from Controllers (compared to ART-suppressed) were enriched for the expression of genes in the Fatty Acid metabolism pathway, which is associated with a quiescent metabolic profile (p<0.05). They also had a higher level of expression of “stem-ness” associated genes, including HOXB7, lower expression of the gene encoding the exhaustion- associated transcription factor Tox, and a distinct DNA methylation pattern in the WNT3 gene body (59% vs 29%methylation, p<0.01). Conclusion: HIV-specific CD8+ T cells from Controllers share several molecular features with long-lived memory CD8+ T cells. The mechanisms by which these pathways may support the persistence of functional HIV-specific T cells remains to be investigated. However, our data provide a rationale for future studies to evaluate Wnt signaling and other programs that control long-lived memory T cells as a target to enhance the efficacy of CD8+ T cell-based HIV cure strategies. 314 PRESERVED TELOMERASE ACTIVITY AND TELOMERE LENGTH IN CD28- CD8 T CELLS IN TREATED HIV Jue Lin , Jeffery Milush, Norman G. Jones, Alexander Carvidi, Heather Hartig, Steven G. Deeks, Jeffrey N. Martin, Sulggi Lee, Elizabeth Blackburn, Peter W. Hunt University of California San Francisco, San Francisco, CA, USA Background: HIV has been proposed as a model of “accelerated immunosenescence,” but short telomere length (TL) and other T cell senescence markers fail to predict clinical outcomes in this setting. We hypothesized that the impaired effector CD8+ T cell maturation observed in treated HIV infection by our group and others might be associated with paradoxically preserved telomerase activity (TA) and TL in these cells. Methods: HIV-infected adults maintaining antiretroviral therapy (ART)- mediated viral suppression (<40 copies/ml) for at least 2 years and age/gender- matched HIV-uninfected participants, all CMV seropositive, were sampled from the SCOPE cohort as part of a study addressing the determinants of influenza vaccine responsiveness. Active viral hepatitis and injection drug use were exclusionary. PBMC were isolated from a large-volume blood draw, sorted into CD8+CD28- and CD8+CD28+ T cell fractions, and assessed for both TL (T/S ratio) and TA (per 10 5 cells). Comparisons between groups and by CD28 status were assessed with linear mixed models, log-transforming biomarkers to satisfy model assumptions. Results: Of 148 HIV–infected ART-suppressed participants and 37 HIV- uninfected controls, most were men (90%) and median age was 54 years (IQR: 49 to 60). Among HIV-infected participants, median current CD4 count was 662 and nadir CD4 count was 299 cells/mm 3 . HIV-infected participants were less likely to be current smokers (12% vs. 33%, P<0.01). In both HIV-infected and –uninfected individuals, older age was strongly associated with shorter TL in both CD28- and CD28+ CD8+ T cells (rho: -0.38 for both, P<0.001) and women had longer TL in CD28+ CD8+ T cells than men (P=0.01). There was no evidence for an association between current smoking and TL in either CD28- or CD28+ CD8+ T cell fractions (P>0.31 for both). After adjustment for age and gender, HIV-infected participants had less of a decline in TL and TA in CD8+ T cells with the loss of CD28 than HIV-uninfected participants (P≤0.031 for all, see figure). Conclusion: Effector CD28- CD8+ T cells exhibit less of a decline in telomere length and telomerase activity in HIV-infected individuals with ART-mediated

Poster Abstracts

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