CROI 2015 Program and Abstracts

Abstract Listing

Oral Abstracts

plasma (P<0.03). Furthermore, rectal cell associated SIV-DNA levels were significantly reduced between d75 and d200 on-ART in IL-21-treated RMs (P<0.01) but not in controls. Finally, only IL-21-treated animals maintained plasma viral loads significantly lower than those at pre-ART up to eight months post-ART interruption. Conclusions: These data provide evidence of a link between mucosal immunity, inflammation, and HIV persistence. Furthermore, they suggest that IL-21 may provide important therapeutic benefits when used as an adjunctive immunomodulatory agent in ART-suppressed HIV-infected individuals. 169 Discovery of CD8 + T Cell Epitopes Encoded by the HIV 5’Leader Sequence Edward Kreider 1 ; Katja J. Pfafferott 2 ;Thomas Partridge 2 ; Hui Li 1 ; RanjitWarrier 1 ; Benedikt M. Kessler 2 ; Andrew J. McMichael 2 ; Persephone Borrow 2 ; Beatrice H. Hahn 1 ; George M. Shaw 1 1 University of Pennsylvania, Philadelphia, PA, US; 2 University of Oxford, Headington, United Kingdom Background: The HIV-1 5’ leader consists of the RNA upstream of canonical coding regions, encodes essential replicative functions, and exhibits the highest degree of conservation within the viral genome. We hypothesized that the 5’ leader, despite its designation as the 5’ “untranslated region,” encodes previously uncharacterized open reading frames (ORFs) that are expressed from AUG-like start codons and harbor epitopes that are recognized by host T cell responses. Methods: Single genome sequencing (SGS) was conducted on plasma virus from HIV-1-infected humans. Interferon- γ ELISPOT and intracellular cytokine staining were performed on PBMCs stimulated with autologous peptides or putative escape variants encoded by the 5’ leader sequence. Mass spectrometry analysis of major histocompatibility complex (MHC)-presented epitopes was conducted on peptides purified using MHC immunoprecipitation, acid elution, and reverse phase liquid chromatography of lysates from HIV-IIIB infected CD4+ T cells. Ribosomal profiling was used to identify AUG-like translation initiation sites. Results: SGS of virus from HIV-1-infected humans demonstrated mutational patterns suggestive of virus escape throughout the 5’ leader. Based on these escape patterns, 4 potential ORFs were identified: one in the transactivation response element (TAR), one within U5, one surrounding the dimerization initiation signal (DIS), and one around the major splice donor. Screening for a T cell response to autologous transmitted/founder and putative escape peptides from these ORFs revealed CD8+ T cell recognition of an epitope within the DIS stem loop ORF. Mass spectrometry analysis of MHC-bound peptides from HIV-IIIB-infected T cells revealed presentation of two overlapping TAR peptides, LA14 and LL8. Ribosomal profiling demonstrated translation initiation at one-off AUGs within these two newly identified ORFs. Analysis of sequences in the Los Alamos HIV compendium showed that 91% of Group M viruses encode a DIS stem loop ORF and 93% of non-Clade A Group M viruses encode a TAR ORF. Conclusions: We report here the discovery of multiple previously unrecognized ORFs in the HIV-1 5’ leader, or 5’ “untranslated region.” Peptides from these ORFs are presented on infected CD4+ T cells and can target these cells for T cell recognition. The discovery of a novel source of T cell epitopes within such a highly conserved and functionally important region of the genome has implications for both vaccine development and immunopathogenesis research. 170LB Neutralizing Antibodies Differ Between HIV-1 – Infected RV144 Vaccinees and Placebos Shelly J. Krebs 1 ; Morgane Rolland 1 ; SodsaiTovanabutra 1 ; Ivelin Georgiev 2 ; Agnes-Laurence Chenine 1 ;Victoria R. Polonis 1 ; Supachai Rerks-Ngarm 3 ; Peter D. Kwong 2 ; Nelson L. Michael 1 ; Jerome H. Kim 1 on behalf of the RV152 Study Group 1 US Military HIV Research Program, Silver Spring, MD, US; 2 Vaccine Research Center, NIAID, NIH, Bethesda, MD, US; 3 Ministry of Public Health, Bangkok, Thailand Background: Elucidating the ontogeny of broadly neutralizing antibodies (NAb) within infected individuals may identify important factors to consider in vaccine development. Although NAbs were not a correlate of risk in the RV144 HIV vaccine trial, B cell priming by vaccination may have accelerated the production of specific NAb lineages after infection. We asked if RV144 vaccine recipients who became infected elicited NAbs that varied in breadth, potency, and specificity compared to RV144 infected placebo recipients. Methods: Samples from 94 infected RV144 individuals were evaluated for NAbs at 1-3 years post-diagnosis prior to the initiation of ART. Using a high-throughput robotic microneutralization assay, samples were analyzed against a panel of 35 viruses from subtypes A, B, C, D, CRF_01 AE, and CRF_02 AG. Included within this panel were 21 pseudoviruses where the pattern of neutralization can predict NAb specificity. Neutralization breadth, potency, and specificity of the responses observed after infection were compared between the vaccine and placebo recipients. Results: Aggregate analysis revealed breadth and potency of neutralization were highly correlated ( ρ = 0.94; p<0.001; Fig.1). Seventeen (29%) placebos while only 3 (10%) vaccine recipients neutralized >50% of the 35 virus panel (Fig.1). At three years post-diagnosis (956-1198 days), 8 placebo and 1 vaccine recipients neutralized >70% of the panel (Fisher’s exact test, p=0.08), noting that the single vaccine recipient had only received 1 out of the 6 RV144 immunizations (Fig. 1). A trend toward increased breadth in the placebo group compared to the vaccine group (median= 40 vs 30, p=0.08) was also observed. The CD4 binding site and/or MPER were predicted as the dominant NAb specificities from both the placebo and vaccine groups, at 77% and 63% respectively.

Oral Abstracts

Conclusions: We report differences in neutralization breadth and potency between infected vaccine and placebo recipients of RV144. These data suggest a restriction in the vaccine group in the ability to produce broad NAb responses post-infection compared to the placebo group, raising the hypothesis that infected vaccinees define a group with intrinsically less effective HIV-1 immune responses. Further studies will provide a better understanding of the development of antibody responses in HIV-1 infected subjects, the potential role of vaccination on post-infection humoral responses, and the interrelationship between HIV-1 evolution and antibody responses.

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CROI 2015