CROI 2015 Program and Abstracts

Abstract Listing

Poster Abstracts

284 Soluble CD40 Ligand Contributes to Dendritic Cell Mediated T-Cell Dysfunction Elizabeth A. Miller; Ramya Gopal;VanessaValdes; Jeffrey S. Berger; Nina Bhardwaj; Meagan O’Brien Icahn School of Medicine at Mount Sinai, New York, NY, US Background: Soluble CD40 ligand (sCD40L) levels are increased during human immunodeficiency virus (HIV) infection, but it is unknown whether monomeric or multimeric forms predominate, and whether there are differential effects of these forms on dendritic cell function and dendritic cell-T cell interactions. Methods: Immunoblots were performed to delineate various forms of sCD40L present in plasma from HIV-infected donors. Monocyte-derived DCs (moDCs) from seronegative donors were exposed to forms of sCD40L prior to Toll-like receptor (TLR) stimulation and moDC function and T cell function was assessed in vitro . Levels of sCD40L in plasma from ART-treated HIV-infected donors before and after low dose aspirin therapy were measured via ELISA. Results: Multiple forms of sCD40L were identified in plasma from ART-treated HIV-infected donors, including monomers, dimers, and trimers. Though monomeric and multimeric forms of sCD40L had differential effects on DC activation when given alone, both strongly suppressed secretion of the Th1 skewing cytokine, IL-12, upon subsequent TLR stimulation. Furthermore, moDC exposed to both monomeric and multimeric sCD40L induced T cell anergy and regulatory T cell formation. One week of low dose aspirin decreased sCD40L in ART-treated HIV infected subjects, suggesting that heightened sCD40L is due in part to platelet activation and is responsive to anti-platelet therapy. Conclusions: Elevated sCD40L during HIV infection contributes to dendritic cell mediated T cell dysfunction. Anti-platelet agents that decrease sCD40L may provide immune modulatory benefits as adjunctive therapies to ART. Background: Plasmacytoid dendritic cells (pDCs) are the main producers of interferon-alpha (IFN α ), a powerful innate antiviral cytokine. IFN α production by pDCs is promoted by their cross-talk with NK cells, which triggers NK cell-cytotoxicity through the up-regulation of the death ligand TRAIL. HIV-1 directly activates pDCs by inducing their maturation and their production of IFN α . HIV-1 is also involved in the differentiation of pDCs into TRAIL-expressing killer cells. The impact of NK cells on IFN-a-production and TRAIL-expression by pDCs in the context of HIV-1 infection is unknown. Given the essential role of both pDCs and NK cells in the control of HIV-1 infection, the objective of this study was to determine the impact of NK-pDC cross-talk on the reciprocal triggering of antiviral activities. Methods: pDCs and NK cells were negatively sorted from PBMC of healthy donors. NK cells were kept either unstimulated (rNK) or activated with PMA/ionomycin for 2 hrs (aNK). pDCs were either uninfected or infected with R5-HIV-1 BAL (pDC HIV ) at various concentrations and co-cultured with NK cells at different ratios for 24 h. The fate of both cell types was studied using multiparametric flow cytometry combined to Multianalyte Profiling technology and Gene array approach. Results: HIV-1 infection of primary pDCs induces the expression of maturation markers (HLA-DR, CD80, CD83, CD86) and the homing receptor CCR7. It also induces the emergence of TRAIL-expressing IFN α -producing pDCs in a dose-dependent manner. At low concentrations of HIV-1, the crosstalk of pDC HIV with aNK cells significantly increased the production of IFN-a, the proinflammatory mediators IL-12, TNF-a and IFN-g and the b-chemokines MIP-1 a and MIP-1 b. It also triggered TRAIL expression on NK cells. At high concentrations of HIV-1, NK cells did not significantly modulate the production of these cytokines and chemokines. Interestingly, the alarmin HMGB1 released by pDCs upon HIV-1 infection, plays an essential role during NK-pDC cross-talk, and its inhibition by Glycyrrhizin, N-Ethylpyruvate or anti-HMGB1 Abs prevented pDCs maturation, the release of IFN α and b-chemokines, and the emergence of TRAIL-expressing NK cells and pDCs. Conclusions: These findings highlight the essential role of NK-pDC HIV cross-talk in the acquisition of effector antiviral functions by pDCs and NK cells and reveal the essential role of HMGB1 during this crosstalk. 286 Dysfunctional Neutrophil Responses to SIV Infection Background: Recent studies indicate that individuals with low neutrophils (PMN) are at increased risk of HIV infection. Also, the RV144 vaccine trial implicated non-neutralizing antibodies and associated Fc-mediated functions in vaccine-induced protection. These studies suggest that early innate antiviral functions and Fc-mediated functions of PMN may play an important role in mediating early viral control, yet the role of innate cellular responses in preventing the establishment of the viral reservoir remains unknown. The potential to contribute to the early control of viral spread may depend on the kinetics of PMN mobilization, activation, and recruitment during acute HIV/SIV infection. Methods: We assessed kinetic changes in PMNs in peripheral and mucosal tissues during acute SIV infection in six rhesus macaques challenged i.r. with 100,000 TCID50 of SIVmac239X. Flow cytometry, CBC, and luminex were used to assess PMN and cytokine levels and related PMN functional markers. Samples were collected pre-SIV and days 3, 7, 14, 21, 28, 42, and 63 post-SIV. Results: We observed trending decreases in systemic IL-17 (p=0.0793) and G-CSF (p=0.0625) early after SIV. In addition, we observed no increase in local IL-8 measured from rectal cytobrush supernatants after infection (p=0.2751). Surprisingly, blood PMN concentrations steadily decreased after infection, and no significant increase of PMN was detected in gut or lymphoid tissues. In addition, blood PMN numbers and rectal PMN percentages significantly correlated (p=0.0032). Lastly, HLA-DR (p=0.0313), CD86 (p=0.0156), and Fc γ RI (p=0.0313) were significantly upregulated on PMN during acute SIV infection. Conclusions: In contrast to other acute viral infections, such as influenza, PMN-supporting cytokines and chemokines are decreased or not induced during acute SIV, potentially contributing to lack of PMN mobilization and recruitment to the tissues. Further, blood and rectum PMN levels correlate post-SIV, suggesting that blood PMN concentration may directly impact recruitment to gut tissues. Lastly, upregulation of markers involved in antigen presentation and Fc-mediated functions highlights the potential diverse functional roles of neutrophils during acute SIV infection and the mechanisms by which neutrophils, if induced, could contribute to more effective viral control. This may represent a mechanism of escape unique to retroviruses by which they dysregulate the cellular innate immune response during acute infection. Tiffany Hensley-McBain 1 ; Laura E. Richert-Spuhler 1 ; Jillian Gile 1 ; MelonT. Nega 2 ;Thomas H.Vanderford 2 ; Jacob D. Estes 3 ; Brandon F. Keele 3 ; Nichole R. Klatt 1 1 University of Washington, Seattle, WA, US; 2 Emory University, Atlanta, GA, US; 3 Frederick National Laboratory for Cancer Research, Frederick, MD, US 285 The Alarmin HMGB1 Is Crucial for the Acquisition of Antiviral pDC Effector Functions Hela Saïdi 1 ; Marlène Bras 1 ; Pauline Formaglio 1 ; Bruno Charbit 1 ; Marie-Thérèse Melki 2 ; Marie-Lise Gougeon 1 On behalf of the Antiviral Immunity, Biotherapy andVaccine Unit 1 Institut Pasteur, Paris, France; 2 Sebia, Evry, France

Poster Abstracts

240

CROI 2015