CROI 2018 Abstract eBook

Abstract eBook

Poster Abstracts

276 SIGNATURES OF PROTECTIVE SIV-SPECIFIC CD8+ T CELLS Carly Elizabeth C. Starke , Jason Brenchley NIH, Bethesda, MD, USA Background: Simian immunodeficiency virus (SIV)-specific CD8+ T lymphocytes can reduce SIV replication, slowing disease progression. However, SIV-specific CD8+ T cells are incapable of reducing viral replication to low levels for the lifespan of most SIV-infected rhesus macaques (RM) and the majority of animals progress to simian AIDS. Recent studies demonstrate that SIV persists in lymphoid follicles, infecting CD4+ follicular helper T (TFH) cells. In rare elite controller Asian macaques, SIV replication is spontaneously controlled and may be attributed to the unique ability of some CD8+ T cells to penetrate into lymphoid follicles and reduce SIV infection of TFH cells. Methods: To determine whether there are signatures of tissue-resident SIV- specific CD8+ T cells associated with increased virologic control, we analyzed molecular and immunological characteristics of SIV-specific CD8+ T cells in lymphoid and gastrointestinal tract tissues of SIV-infected viremic controller (≤10,000 copies/mL) and noncontroller (>10,000 copies/mL) RM. MHC-I tetramers loaded with SIV epitopes were used to identify SIV-specific CD8+ T cells and flow cytometric, gene chip, and T cell receptor (TCR) clonotypic analyses were used to measure phenotypic and functional qualities. Results: While we found no differences in the magnitude of SIV-specific T cell responses based upon the ability to control viral replication, RM controllers exhibited increased CXCR5 expression in lymphoid tissues compared to RM noncontrollers. Additionally, frequencies of SIV-specific CD8+ T cells correlated with CD4+ T cell count and frequencies of CXCR5+ SIV-specific CD8+ T cells negatively correlated with plasma RNA viral load and viral DNA within TFH cells. TCRβ clonotypic analysis revealed that CDR3 length distribution was biased towards CDR3s with a length of 14aa, including all public clonotypes, and the TCR repertoire of controllers was more diverse than that of noncontrollers with public clonotypes and some V and J gene segments appearing more frequently. Conclusion: Our data suggest that inherent functionality and particular trafficking of SIV-specific CD8+ T cells may be important for virologic control. The increased CXCR5 expression by SIV-specific CD8+ T cells of RM controllers may suggest an ability of CD8+ T cells to enter the follicle and reduce viral loads. Understanding the role of SIV-specific CD8+ T cells and the mechanisms that underlie viral control in SIV pathogenesis may lead to improved vaccine and therapeutic development. 277 TCF-1 EXPRESSION IS ASSOCIATED WITH HIV-SPECIFIC CD8+ T CELL PROLIFERATIVE CAPACITY Rachel L. Rutishauser 1 , Christian Deo T. Deguit 1 , Rebecca Hoh 1 , Michelle A. Hough 1 , Melissa Krone 1 , Rafick-Pierre Sekaly 2 , Frederick M. Hecht 1 , Christopher D. Pilcher 1 , Jeffrey N. Martin 1 , Steven G. Deeks 1 , Joseph M. McCune 1 , Peter W. Hunt 1 1 University of California San Francisco, San Francisco, CA, USA, 2 Case Western Reserve University, Cleveland, OH, USA Background: Many HIV cure strategies propose to elicit HIV-specific CD8+ T cell responses to control and/or eradicate the virus, but they will not be effective if they do not prevent or reverse CD8+ T cell exhaustion. A loss in proliferative capacity is a key feature of exhaustion, but little is known about how this capacity is regulated in these cells. The purpose of this study was to explore the connection between TCF-1, a Wnt-signaling transcription factor, and proliferative capacity in HIV-specific CD8+ T cells. Methods: Cryopreserved PBMCs were sampled from Viremic (VL>8,000 copies/mL; n=14), ART-suppressed (VL<40 copies/mL on stable ART for a median of 2 years; n=10), and Controller (VL<40 copies/mL not on ART; n=12) HIV-infected individuals. Using flow cytometry, HIV-specific CD8+ T cells were identified by staining with Gag, Pol, or Nef-specific MHC Class I (HLA-A*02, *03, *24, or -B*07)-restricted tetramers. Tetramer+ cells were characterized for the expression of transcription factors (TCF-1, Tbet), effector molecules (Granzyme B, Perforin), and surface proteins (PD-1, CD127, CCR7). Proliferation of the tetramer+ population was measured after 6-day in vitro peptide stimulation of CellTraceViolet (CTV)-labeled cells. Results: HIV-specific tetramer+ CD8+ T cells from Controllers compared to Viremic individuals had greater proliferative responses (%CTVlo 89% vs. 16%; p=0.05; measured in a subset of individuals), were more likely to express CD127 (26% vs. 7%; p=0.0001), and were less likely to express PD-1 (60% vs. 95%; p<0.0001). Median TCF-1 expression was highest in tetramer+ cells from Controllers, followed by ART-suppressed and then Viremic individuals (62% vs. 51% vs. 35%; p<0.0001). TCF-1 expression in these cells was associated with

higher CCR7 and CD127, and lower PD-1, Granzyme B, and Tbet expression. Strikingly, expression of TCF-1 (but not PD-1) strongly correlated with proliferative capacity amongst Viremic and Controller individuals (r=0.83, p=0.0008), and was inversely correlated with HIV VL in Viremic individuals (r=-0.85, p=0.02). Conclusion: TCF-1 expression marks subpopulations of less terminally differentiated tetramer+ HIV-specific CD8+ T cells whose abundance correlates with enhanced proliferative capacity. Whether preservation of TCF-1+ cells is required to prevent HIV-specific T cell exhaustion remains to be investigated, but these data provide a rationale for future studies to evaluate TCF-1 as a target to enhance the efficacy of CD8+ T cell-based HIV cure strategies.

Poster Abstracts

278 LONGITUDINAL T CELL RESPONSES IN HIV-EXPOSED INFANTS WITH CONGENITAL CMV INFECTION Pamela M. Odorizzi 1 , Rachel L. Rutishauser 1 , Ruth Cortado 2 , Margaret Feeney 1 , Trevor Burt 1 , Karin Nielsen-Saines 2 , Deborah Persaud 3 , Yvonne Bryson 2 , Joseph M. McCune 1 1 University of California San Francisco, San Francisco, CA, USA, 2 University of California Los Angeles, Los Angeles, CA, USA, 3 Johns Hopkins University, Baltimore, MD, USA Background: Congenital CMV (cCMV) infection has a significant impact on pediatric health and affects 0.5-2% of live-born infants worldwide. The rate of cCMV infection is higher amongst children born to HIV-infected mothers, including those who are HIV-exposed but uninfected (HEU). HEU infants are also at higher risk of morbidity from other severe infectious diseases. While many factors likely contribute to this increased risk, the impact of cCMV infection on immune responses in HEU infants is unknown. The goal of this study was to determine how cCMV in HEU infants impacts global CD4+ and CD8+ T cell responses over the first 3 months of life. Methods: Cryopreserved PBMCs were obtained from HEU infants who were either diagnosed with cCMV at birth (CMV detected by PCR in the urine, HEU:CMV+) or who were CMV-negative at birth (HEU:CMV-; n=6 infants per group). Longitudinal samples from three time points (2, 6, and 12 weeks of age) were evaluated. CD4+ and CD8+ T cells were stained and evaluated by flow cytometry to determine the expression of effector-memory markers (CD45RA, CCR7). The expression of effector proteins (e.g., Tbet, Granzyme B) and chemokine receptors that delineate CD4+ T cell subsets (e.g., Th1, Th17, Treg) was characterized on non-naïve T cells. Results: Compared to HEU:cCMV- infants, 2 week old HEU:cCMV+ infants form a large population of non-naïve effector CD8+ T cells that express Tbet (66% vs. 15%; p=0.002) and Granzyme B (62% vs. 1%; p=0.002). This profound effector- differentiated CD8+ T cell response is stably maintained at 6 and 12 weeks. While there is less of an effect on CD4+ T cell responses, cytotoxic non-naïve CD4+ T cells are also found at higher frequency at 2 weeks of age in HEU:cCMV+ compared to HEU:cCMV- infants (%Granzyme B+ non-naïve CD4+ T cells: 0.75% vs 0.006%; p=0.002). Conclusion: cCMV infection in HEU infants induces the generation of a effector-differentiated CD8+ T cells and, to a lesser extent, CD4+ T cells that

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CROI 2018