CROI 2015 Program and Abstracts

Abstract Listing

Oral Abstracts

In rare bnAb-virus combinations, inhibition capacities proved comparable for both transmission modes but no bnAb that potently blocked cell-cell transmission over a range of HIV-1 strains could be identified. Likewise, the capacity of bnAbs to block HIV infection post CD4 engagement differed among virus strains and bnAbs tested. Importantly, mathematical analysis employed to estimate the consequences of the observed activity loss during cell-cell transmission indicated an increased probability of viral resistance mutations to arise in cell-cell rather than free virus spread. Conclusions: Our data suggest that the efficacy of bnAbs during cell-cell transmission cannot be predicted by their free virus activity and greatly differs in a strain-dependent manner. Potent inhibition of both transmission routes will only be possible through a combination of bnAbs, either by multi-component vaccines or antibody cocktails in passive immunization. 166 Peripheral T Follicular Helper Cells With Universal Helper Activity in HIV Infection Bruce Schultz; Alexander Oster; Franco Pissani; Jeffrey E.Teigler; Michael A. Eller; Merlin L. Robb; Jerome H. Kim; Nelson L. Michael; Diane Bolton; Hendrik Streeck US Military HIV Research Program, Silver Spring, MD, US Background: Immunogen design to generate protective neutralizing antibodies is a central effort in HIV vaccine development and critically dependent on T follicular helper (T FH ) cells. However, very little is known about the peripheral counterpart of HIV-specific T FH cells and the protein-specific help they might provide. Methods: Biomark Fluidigm gene expression profiles from HIV-specific IL-21+ and IFN γ + CD4 T cells were analyzed from chronic, treatment-naïve HIV-infected individuals. Epitope specificity of peripheral T FH cells and Th1 cells was defined by Elispot. HIV-specific T FH cell lines were generated and their functionality and phenotype assessed by flow cytometry. Helper activity of Gag-and Env-specific T FH cells were tested in a CD4-B cell as well as CD4-CD8 T cell co-culture assay. HIV-specific T FH responses from ALVAC/AIDSVAX and DNA/Ad5 vaccine recipients were also compared. Results: HIV-specific IL21+CD4 T cells showed significantly higher expression of genes associated with T FH cells compared to IFN γ + or IL21+/IFN γ + CD4 T cells including BCL6, cMaf and CXCR5. IL21+CD4 T cells most closely resembled T FH cells compared to any other phenotypic description of pT FH cells. Besides CXCR5+, HIV-specific pT FH cells predominantly expressed ICOS and PD1 but were CCR7-. The frequency of HIV-specific pT FH cells was low when compared to HIV-specific IFN γ +CD4 cells (p<0.0001). Interestingly, while HIV- specific IFN γ +CD4 T cells dominantly targeted epitopes in Gag, HIV-specific T FH cells equally recognized epitopes within Gag and Env (p=0.0009). Gag- and Env-specific T FH cells were able to provide help to HIV-specific CD8 T cells in vitro , characterized by Perforin/GrzB induction. In contrast, however, Gag-specific T FH cells preferentially induced maturation and proliferation of B cells, while Env-specific T FH cells predominantly drove Ig class switching. Further analysis revealed that Env-specific T FH cells also displayed features indicative of Th2 cells compared to Gag-specific T FH responses (p=0.0003). Lastly, we found that ALVAC/AIDSVAX vaccine recipients had significantly higher levels of HIV-specific pT FH cells but comparable levels of HIV-specific Th1 cells as DNA/Ad5 vaccine recipients. Conclusions: Given the evidence presented here for the role that IL21+CD4 T cells appear to play in the maturation of vaccine evoked humoral immune responses, these findings have clear implications for HIV vaccine design. 167 Redirected Killing of HIV-Infected T Cells by Germinal Center CD8 T Cells Constantinos Petrovas 1 ; Sara Ferrando-Martinez 1 ; Michael Gerner 2 ; Amarendra Pegu 1 ; Perla Del Río-Estrada 3 ; Kristin Boswell 1 ; Manuel Leal 4 ; Gustavo Reyes-Teran 3 ; Ronald Germain 2 ; Richard A. Koup 1 1 Vaccine Research Center, National Institute of Allergy and Infectious Diseases, Bethesda, MD, US; 2 NIAID-NIH, Bethesda, MD, US; 3 Instituto Nacional de Enfermedades Respiratorias, Mexico City, Mexico; 4 Instituto de Biomedicina de Sevilla, Sevilla, Spain Background: Follicular helper CD4 T cells (T FH ) are located within the germinal centers (GC) of lymph nodes (LN) and represent a major contributor to the latent reservoir. Bispecific antibodies that target HIV Env and CD3 are being developed to eliminate the latent reservoir by activating HIV from CD4 T cells and inducing killing of those cells by CD8 T cells. We characterized the localization, frequency, and function of CD8 T cells in GCs to determine if they were present and capable of killing HIV-expressing cells in the context of HIV Env/ CD3-targeting bispecific antibodies. Methods: The phenotype, localization and function of CD8 T cells in tonsils and LNs from non-infected and HIV-infected viremic individuals was investigated. Polychromatic flow cytometry was used for phenotypic analysis and confocal imaging for spacial localization. Histo-Cytometry was performed for the quantitative analysis of GC cell populations. Function (IFN, TNF, MIP-1, and Perforin, GzB production) was assessed by intracellular staining after stimulation with anti-CD3. (5 hour). In vitro cytolytic activity of sorted CD8 T cell populations was tested in a killing assay using an anti-HIV Env/anti-CD3 bispecific-antibody. Cytokines and soluble cell death mediators were analyzed by Luminex. Results: Phenotypic analysis of tonsillar cells revealed a memory population of CD8 T cells expressing a CCR7 low CXCR5 high profile compatible with follicular localization. Histo- Cytometry analysis confirmed the presence of a small population of CD8 T cells within the GC. These GC CD8 T cells were expanded in HIV-infected LNs compared to non-infected tonsils. Follicular CD8 T cells (defined by CXCR5 expression and loss of CCR7) exerted a superior killing capacity judged by in vitro mobilization of GzB/Perforin. Production of MIP-1 and GzB predominated over IFN and TNF production in GC CD8 T cells. Of all tissue CD8 T cell populations tested, GC localized CD8 T cells had the greatest ability to mediate killing of HIV-infected target cells after cross-linking with an anti-HIV Env/anti-CD3 bispecific antibody. Conclusions: HIV infection is characterized by accumulation of CD8 T cells within LN follicles. These CD8 T cells are functionally capable of mediating bispecific antibody-mediated killing of HIV-infected CD4 T cells. These data add credence to the use of bispecific antibody therapy to purge the LN reservoir 168 IL-21 Reduces Inflammation and Virus Persistence in ART-Treated SIV-Infected Macaques Luca Micci 1 ; Emily Ryan 1 ; Colleen McGary 1 ; Sara Paganini 1 ; Guido Silvestri 1 ; Mike Piatak 2 ; Jeffrey Lifson 2 ; FrancoisVillinger 1 ; Jason M. Brenchley 3 ; Mirko Paiardini 1 1 Yerkes National Primate Research Center, Emory University, Atlanta, GA, US; 2 Leidos Biomedical Research, Inc, Frederick, MD, US; 3 National Institute of Allergy and Infectious Diseases (NIAID), Bethesda, MD, US Background: Residual inflammation persists and critically contributes to non-AIDS-related morbidity/mortality in ART-treated, HIV-infected subjects. Furthermore, inflammation may contribute to HIV persistence during ART. Interleukin (IL)-21 regulates the differentiation and maintenance of IL-17- and IL-22- producing CD4 T cells, which depletion critically contributes to chronic immune activation and disease progression in HIV and SIV infection. In this study, we investigated the effects of Interleukin (IL)-21 administration in chronic, ART-treated SIV-infected rhesus macaques (RMs) on mucosal integrity, residual inflammation, and virus persistence. Methods: Sixteen RMs were infected with SIV mac239 i.v. and, starting at day 60 post-infection, treated for seven months with PMPA, FTC, Raltegravir, Darunavir and Ritonavir. Eight RMs received IL-21-Fc (100 mg/kg, s.c., weekly for six weeks) at the beginning and the end of ART, with the other eight serving as ART- treated controls. Blood, lymph nodes and rectumwere longitudinally collected, and the effects of IL-21 on inflammation, T cell subset levels, and viral persistence assessed. The Mann-Whitney test was used for statistical analyses. Results: ART was very effective, with fully suppressed plasma viremia (<60 SIV-RNA copies/ml) in all RMs. Compared to ART-controls, ART+IL-21 RMs showed improved restoration of intestinal Th17 and Th22 cells (P<0.01 for both subsets). Remarkably, IL-21-treated RMs showed a faster and more pronounced reduction in the levels of activated (HLA-DR + CD38 + ) and proliferating (Ki-67 + ) T cells in rectum and blood during ART (P<0.01), and maintained level of T cell activation significantly lower than controls up to eight months following ART-interruption (P<0.01). Between days 75 to 200 on-ART, IL-21-treatment elicited a higher number of RMs with undetectable (<3 copies/mL) SIV-vRNA in

Oral Abstracts

179

CROI 2015