CROI 2016 Abstract eBook

Abstract Listing

Oral Abstracts

Methods: Rhesus macaques were infected IV with SIVmac239. On day 7 (acute infection), 6 animals were sacrificed and lymph nodes (LN), spleen, and rectum harvested and snap frozen in OCT. Three animals underwent LN biopsy (day 42), treatment with CD8 depleting antibody (day 60), and necropsy on day 84 . In situ hybridization for SIV RNA and immunostaining for Ki67, CD4, and CD20 were performed to determine frequencies of SIV RNA+ cells and target cells within F and EF. Wilcoxon matched-pairs signed rank test was used to determine significance. Results: In acutely infected animals, frequencies of SIV RNA+ cells did not differ significantly in F vs EF of LN (median F:EF 1.2, p=0.6), but were higher in F vs EF in spleen (median F:EF 3.7, p=0.03) and rectum (median F:EF 17; p=0.03). After adjusting for Ki67+CD4+ cells in each compartment, there was a trend in all tissues for more SIV RNA+ to be in F vs EF (medians F:EF: LN 2.2; p=0.06; spleen 1.7; p=0.12; rectum 2.3, p=0.06). In chronically infected animals prior to CD8 depletion, frequencies of SIV RNA+ cells in LN were 2.8- to 60-fold higher in F vs EF. After controlling for Ki67+CD4+ cells, SIV RNA+ cells were 11- to 40-fold higher in F vs EF. Following documented CD8 depletion of LN, differences in F vs EF largely abated with the LN F:EF ratio ranging from 0.7-1.8. This was primarily due to increases in SIV RNA+ cells in EF (range, 4- to 56-fold more vs pre-depletion LN), while increases in F were smaller (range, 1.2-1.9 fold more vs pre-depletion LN). Ki67+CD4+ cell frequencies were not substantially altered by CD8 depletion. After adjusting for Ki67+CD4+ cells, frequencies of SIV RNA+ cells were consistently higher in F vs EF of LN post CD8 depletion (range, F:EF 1.4 to 7.2). Conclusions: In the absence of virus-specific CTL, the concentration of virus-producing cells in B cell follicles is attenuated, but not eliminated. These data support the hypothesis that virus-specific CTL play a key role in virus compartmentalization, and further suggest that T follicular helper cells are inherently more permissive to SIV than other cells. 24 Sooty Mangabey CD4+ T Cells Express the SIVsmm Coreceptor CXCR6 KatherineWetzel 1 ; Emily Roberts 1 ;YanjieYi 1 ; Michael R. Betts 1 ; Guido Silvestri 2 ; Mirko Paiardini 2 ; Ronald Collman 1 1 Univ of Pennsylvania, Philadelphia, PA, USA; 2 Yerkes Natl Primate Rsr Cntr, Emory Univ, Atlanta, GA, USA Background: Nonpathogenic SIVsmm infection of sooty mangabeys (SM) is characterized by limited infection of certain CD4+ T cell subsets, such as central memory T cells. One mechanism that may contribute to limited infection of certain cells is extremely low expression of CCR5 by SM and other natural hosts. However, SM exhibit high viral loads despite little CCR5. Our lab has demonstrated that SIVsmm infection occurs in vivo in the absence of CCR5 and that smCXCR6 supports SIVsmm infection in vitro and in smPBMC ex vivo. We hypothesize that CXCR6 is a principal coreceptor in SM, and that CXCR6 expression by expendable CD4+ T cell subsets enables viral replication in CCR5-low natural hosts without either disruption of CD4+ T cell homeostasis or pathogenesis. Our aimwas to define expression patterns of CXCR6 on CD4+ T cells of SM, as well as rhesus macaques (RM). We also examined GPR15, which has modest coreceptor activity in vitro. Methods: Because anti-human CXCR6 reagents do not cross-react with smCXCR6 or rmCXCR6, we generated a novel monoclonal antibody by immunizing mice with B78H1 cells transduced to express smCXCR6. This antibody specifically reacts with all primate CXCR6 molecules tested. Using flow cytometry, we defined expression patterns of CXCR6, GPR15 and CCR5 on both resting and ConA/IL-2-stimulated CD4+ T cells from uninfected SM and RM. Results: Both CXCR6 and GPR15 were expressed on resting memory CD4+ T cells of SM and RM. Notably, CXCR6, GPR15 and CCR5 expression defined three distinct populations of resting CD4+ T cells in both species, with few cells expressing multiple coreceptors. Upon stimulation, the proportion of CXCR6+ CD4+ T cells increased in both SM and RM. In stark contrast, CCR5+ CD4+ T cells increased in RM but not SM following stimulation, as previously reported. As a result, CXCR6+ cells substantially outnumbered CCR5+ cells among SM CD4+ T cells. Conclusions: CXCR6 defines a CD4+ T cell population in SM that is distinct from CCR5-expressing cells, and may identify a unique subset that can support SIVsmm replication without pathogenic consequences. The divergent changes in CCR5 and CXCR6 expression in response to stimulation suggest that CXCR6 and CCR5 expression are controlled by distinct mechanisms. Delineating the specific T cell subsets that express CXCR6 in blood as well as in tissues will help determine how CXCR6 targets SIV in SM, and in the setting of very low CCR5 expression, contributes to nonpathogenic consequences of infection. 25 Safety, Immunologic and Virologic Activity of Anti-PD-L1 in HIV-1 Participants on ART Joseph J. Eron Jr 1 ; Cynthia Gay 1 ; Ronald Bosch 2 ; Justin Ritz 2 ; Jason M. Hataye 3 ; Carey Hwang 4 ; Randall L.Tressler 5 ; StephenW. Mason 6 ; Richard A. Koup 7 ; JohnW. Mellors 8 ; for the ACTG A5326 StudyTeam 1 Univ of North Carolina at Chapel Hill, Chapel Hill, NC, USA; 2 Harvard Sch of PH, Boston, MA, USA; 3 NIH, Bethesda, MD, USA; 4 Bristol-Myers Squibb, Princeton, NJ, USA; 5 DAIDS, NIAID, NIH, Rockville, MD, USA; 6 Bristol-Myers Squibb, Wallingford, CT, USA; 7 VRC, NIAID, NIH, Bethesda, MD, USA; 8 Univ of Pittsburgh, Pittsburgh, PA, USA Background: HIV-1 infected persons with viremia suppressed on antiretroviral therapy (ART) have persistent T-cell exhaustion that may limit clearance of HIV-1 expressing cells. Monoclonal antibodies (mAbs) targeting the PD1:PD-L1 axis have shown clinical activity in cancer studies. Blocking this axis in patients suppressed on ART may improve HIV-1 specific immune responses.

Oral Abstracts

Methods: In a pre-specified analysis of an initial dosing cohort of ACTG 5326, 8 HIV-infected participants on ART with HIV-1 RNA <40 c/mL and ≥0.4 c/mL by single copy assay (SCA) received one infusion (double-blind) of anti PD-L1 mAb (BMS-936559) at 0.3 mg/kg (N = 6) or normal saline (NS) (N=2). Anti-PD-L1 pharmacokinetics and receptor occupancy (RO) on CD3+, CD4+ and CD8+ T cells were measured and safety was assessed. HIV-1 Gag-specific CD8+ T cell responses, plasma HIV-1 RNA by SCA, and CD4+ T cell-associated (CA) RNA and DNA by qPCR were measured at pre-entry, entry and over 28 days post infusion. In participants who received active mAb, pre-entry/entry (BL) and all post-infusion values were averaged and compared (paired t-test). Results: BMS-936559 was well tolerated; all treatment-related adverse events were mild/moderate. Plasma half-life of BMS-936559 was 3.7 days. RO peaked at 80-100%within 2 hours of dosing and was <20% in 5 of 6 participants by week 4. The average percentage of HIV-1 Gag-specific CD8+ cells (by IFNg (Figure) or CD107a) increased over the 28 days post infusion (p=0.14 and 0.09, respectively), as did polyfunctionality of the Gag-specific CD8+ T cell response, all driven by two strong responders in the anti-PD-L1 treated group. SCA levels appeared to decrease at 3d then increase at 7d (Figure). There was no change in the average SCA HIV RNA or CA-HIV RNA from pre-infusion through Day 28 (p=0.69 and 0.53). CA-RNA:DNA ratio did not change. At 36 weeks post-infusion of anti-PD-L1 mAb or NS, an asymptomatic participant with a previously normal cortisol had an abnormally low AM level and was diagnosed with pituitary insufficiency.

Conclusions: This is the first prospective study of a PD1:PD-L1 axis inhibitor in HIV-infected participants on ART. Despite the low anti PD-L1 dose, there was a trend toward increased HIV-1 Gag specific CD8+ T cell responses over 28 days post-infusion, including increased CD107a expression consistent with reversal of CD8+ T cell exhaustion. Responses were larger in a subset, consistent with responses to immune checkpoint mAbs in cancer treatment and animal models of viral infections.

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CROI 2016