CROI 2016 Abstract eBook

Abstract Listing

Poster Abstracts

252 IL-7 Responsiveness Is Impaired in CD4 T Cells FromHIV Immune Failure Patients Thao Nguyen ; Michael M. Lederman; Scott M. Sieg Case Western Reserve Univ, Cleveland, OH, USA

Background: Despite prolonged HIV suppression with anti-retroviral therapy (ART), some patients fail to recover normal CD4 T cell numbers. These patients are referred to here as “immune failure” (IF) patients. Here, we test the hypothesis that CD4+ T cell responses to the homeostatic cytokine, interleukin-7 (IL-7), are impaired in IF patients, potentially contributing to poor CD4 T cell reconstitution. Methods: PBMC were obtained from IF patients (n=13), immune success patients (n=12) and healthy control donors (n=9). IF was defined by at least 2 years of ART and current CD4 count <380, while IS was defined by at least 2 years of ART and current CD4 count >500. Freshly isolated PBMC were examined for expression of CD127 (IL-7R) among CD4+ T cell subsets. Additional PBMC were labeled with CFSE and stimulated with rIL-7 (5 ng/ml). IL-7 induced CD25 expression was measured overnight by flow cytometry. IL-7 induction of P-STAT5 and P-AKT was measured at day 3 by phosflow and IL-7 induction of proliferation (CFSE dye dilution) was assessed after 7 days. Results: We found defects in IL-7 induced proliferation (p= 0.019) and CD25 surface expression (p= 0.0081) in CD4 T cells from IF patients when compared to IS and HC donors. In contrast, IL-7 induced P-Akt and P-STAT5 were not diminished in CD4 T cells from IF patients. There was a trending relationship between CD127 surface expression and IL-7 induced CD25 expression (r= 0.5727, p= 0.0708). In contrast, CD127 expression did not correlate with IL-7 induced proliferation (r= 0.3, p= 0.3713). Conclusions: These results demonstrate that IL-7 responsiveness is impaired in CD4 T cells from immune failure patients and may contribute to incomplete CD4 T cell recovery in HIV infected patients. These results also indicate that deficiencies in CD127 expression may not sufficiently explain impaired IL-7-induced proliferation in T cells from IF patients and the mechanism of impaired IL-7-induced proliferation is likely complex. 253 Does Reduced HLA-I Downregulation by HIV-2 Nef Contribute to “Functional Cure”? Sophie M. Andrews 1 ; ChisatoYamada 2 ; Simon Brackenridge 1 ;Thushan de Silva 3 ;Tao Dong 1 ; Sarah L. Rowland-Jones 1 1 Univ of Oxford, Oxford, UK; 2 Hokkaido Univ, Sapporo, Japan; 3 Univ of Sheffield, Sheffield, UK Background: The HIV-1 accessory protein nef mediates downregulation of HLA-I molecules to evade recognition of infected cells by cytotoxic T lymphocytes (CTL). Disparate HLA-I molecules are downregulated to differing extents by nef from the laboratory-adapted HIV-1 strain SF2, with HLA-B exhibiting increased resistance, consistent with the observation that HLA-B-restricted responses exert better control on the virus. Primary isolates of HIV-2 nef have however been little studied. The clinical course of HIV-2 infection differs from HIV-1 in that a large proportion of patients are viral controllers, with very similar characteristics to the state of “functional cure” in post-treatment HIV-1 controllers. We aimed to determine whether such viral control was related to the ability of HIV-2 nef to downregulate HLA-A, -B and -C molecules, using nef genes derived from patients with distinct clinical outcomes. Methods: We transiently transfected a series of 16 transgenic cell lines stably expressing chimeric HLA-I alleles, combining cell-surface HLA-A2 with cytoplasmic tails from the major A, B and C families. Cells were transfected with IRES expression vectors containing the nef gene of interest and a fluorescent reporter. The resulting downregulation of surface HLA-A2 was measured using flow cytometry. As controls, cells were also transfected with empty vectors, vectors containing SF2, or one of 8 primary HIV-1 subtype B’ nef alleles. Results: None of the patient-derived HIV-2 nef alleles mediated differential downregulation of HLA-A and -B molecules. Moreover, some patient nef alleles failed to downregulate any HLA-I molecules, but this was not associated with clinical status. Of the HIV-2 nef alleles that did downregulate HLA-I, the extent of downregulation did not differ substantially from HIV-1 nefs. Conclusions: We conclude that primary HIV-2 patient nef isolates do not elicit differential HLA-I downregulation in vitro , in contrast to that reported in HIV-1. This may explain the lack of association between HLA-B alleles and good clinical outcome in HIV-2 infection. However the extent of HLA-I downregulation in these patients did not correlate with clinical parameters, so is unlikely to explain the stronger HIV-specific CTL response in HIV-2 viral controllers. Differential HLA-I downregulation is also unlikely to account for the reduced immunogenicity of HIV-2 nef: we are now investigating whether abrogated proteasomal processing explains this phenomenon. 254 Selective Loss of T-bet and Eomes in HIV-Specific CD4+ T Cells During HIV Infection Marcus Buggert 1 ; Marianne Jansson 2 ; Korey Demers 1 ; JohannaTauriainen 3 ; Anders Sönnerborg 3 ; Michael A. Eller 4 ; Merlin L. Robb 4 ; Steven G. Deeks 5 ; Annika Karlsson 3 ; Michael R. Betts 1 1 Univ of Pennsylvania, Philadelphia, PA, USA; 2 Lund Univ, Lund, Sweden; 3 Karolinska Inst, Stockholm, Sweden; 4 US Military HIV Rsr Prog, Walter Reed Army Inst of Rsr, Silver Spring, MD, USA; 5 Univ of California San Francisco, San Francisco, CA, USA Background: T-bet and Eomesodermin (Eomes) are key transcription factors that govern critical antiviral Th1-type CD4+ and CD8+ T cell functions, including cytokine responses, tissue trafficking, memory formation, exhaustion, and cytolytic activity. Loss of T-bet and heightened Eomes expression in CD8+ T cells are associated with T cell exhaustion and loss of cytolytic potential in progressive HIV infection. Given the importance of these transcription factors for effective anti-viral T cell immunity, we here examined whether changes of T-bet and Eomes expression in CD4+ T cells could be linked to progressive disease and CD4+ T cell dysfunction.

Poster Abstracts

98

CROI 2016