CROI 2018 Abstract eBook

Abstract eBook

Poster Abstracts

assessed with multivariable linear regression on log-transformed CD4+β7hi expression. Results: All patients had a history of injecting drugs with 39% actively using injection drugs at the time of sample collection. CD4+ T cell expression of β7 integrin was within range of previously described values (median = 7.8%, IQR = 6.1-11.9%). CD4+β7hi cell levels were stable over a one year period in 10 individuals (p = 1.00). No sex difference in β7 expression was observed in multivariate analysis. Black PWID had a higher frequency of CD4+β7hi cells than white PWID (median = 10.9% vs. 6.7%, respectively; p < 0.0001). Black PWID also had higher proportions of CD4+CCR6+ cells than white PWID (median = 29.6% vs. 18.5% of total CD4+; p < 0.0001). CD4+CCR6+ cells were more likely to be β7hi than CD4+CCR6- cells (median= 12.6% vs. 5.4%; p < 0.0001) and CD4+CCR6+β7hi cells were highest in black PWID. Conclusion: Black PWID have significantly higher levels of α4β7 expression compared to white PWID similar to previous findings in MSM. Our results further indicate that this difference is associated with higher proportions of β7hi expressing CCR6+ Th17 cells among black PWID, which may contribute to increased risk of HIV acquisition in black compared to white populations.

the binding affinity of AP-2a likely mediates the observed effect on TAPBP expression. We hypothesize that the lowered expression of TAPBP may alter TAPBP-dependent HLA-B expression and antigen presentation and thus affects CD8+ T cell development. These effects may be important to keep in mind for vaccine studies and further understanding of HIV pathogenesis.

Poster Abstracts

207 CELL RECRUITMENT EVENTS DURING THE MENSTRUAL CYCLE ASSOCIATE WITH SHIV SUSCEPTIBILITY Alison S. Kohlmeier , Ivana Massud, Susan Ruone, Mian-er Cong, James Mitchell, Frank Deyounks, Gerardo Garcia-Lerma CDC, Atlanta, GA, USA Background: The luteal phase of the menstrual cycle represent a time point of increased susceptibility to sexually transmitted infections (STIs) including HIV. During the luteal phase, proinflammatory cytokines produced from the female reproductive tract (FRT) promote leukocyte trafficking from the circulation to drive local tissue remodeling and menstruation. We performed a longitudinal immune characterization from PBMC of pigtail macaques to identify FRT recruitment events and understand when SHIV infection is more likely to occur. Methods: Blood PBMC was collected from pigtail macaques (n=6) undergoing weekly vaginal challenges with 50 TCID50 doses of SHIV162p3 (SHIV) during the course of 9 weeks (2 menstrual cycles). NK, B and T cells, monocytes, and professional antigen presenting cells were measured for population frequency of the viable leukocyte pool using flow cytometry. Total CD4 and CD8 T cells were similarly evaluated for CCR5 expression. Plasma samples collected weekly were analyzed for progesterone levels using an enzyme immunoassay (EIA). SHIV infection status was monitored by serology and RT-PCR. Results: Consistent with the known increase of NK cells in the FRT during the luteal phase of the menstrual cycle, elevated progesterone levels from typical uninfected cycling animals significantly associated with a reduced frequency of NK cell populations (p=0.005); likely reflecting FRT recruitment. Unexpectedly, the reduced NK population was associated with decreased T cell population frequency (p=0.03) and increased CCR5 expression frequency on CD4 T cells (p=0.09). As CCR5 is a chemokine receptor important for T cell trafficking into sites of inflammation and a coreceptor of HIV, we notably found that in seroconverted animals, increased CCR5 CD4 T cells and decreased CD3 populations were detected at the estimated time of infection. At the estimated time of infection, 4 out of 4 animals exhibited below average CD3 frequency and above average CCR5 expression on CD4 T cells, and 3 out of 4 animals exhibited below average NK frequency. Conclusion: We found that changes in the frequency of circulating NK and T cell populations, likely correlating with FRT recruitment during the luteal phase of the menstrual cycle, also associated SHIV susceptibility. These data suggest that evaluating circulating leukocyte measurements may refine our understanding of luteal phase susceptibility and provide a useful biomarker to study HIV infection from vaginal exposure.

206 5’ UTR SNP RS111686073 MODIFIES EXPRESSION OF TAPASIN IN BLACKS Victoria E. Walker-Sperling 1 , Veron Ramsuran 2 , Vivek Naranbhai 3 , Maureen Martin 1 , Hongchuan Li 1 , Stephen K. Anderson 1 , Louis-Marie Yindom 4 , Sarah Rowland-Jones 4 , Krista Dong 3 , Thumbi Ndungú 5 , Bruce D. Walker 3 , Mary Carrington 1 1 National Cancer Institute, Frederick, MD, USA, 2 CAPRISA, Durban, South Africa, 3 Ragon Institute of MGH, MIT and Harvard, Cambridge, MA, USA, 4 University of Oxford, Oxford, UK, 5 University of KwaZulu-Natal, Durban, South Africa Background: Tapasin (hereafter TAPBP) is a transmembrane glycoprotein mediating the binding of TAP and MHC-I within the peptide loading complex in the endoplasmic reticulum, the interaction of which is important for optimal peptide loading. Absence of TAPBP in mice is known to affect MHC-I expression and CD8+ T cell development, and viruses such as cytomegalovirus are known to inhibit TAPBP gene transcription to impair antigen presentation in infected cells. Due to the importance of TAPBP in antigen presentation and T cell development, we hypothesized that expression of TAPBP would also affect HIV pathogenesis, and the genetic markers of expression could potentially serve as indicators for risk in the context of HIV outcome. Thus, we decided to examine the TAPBP gene to identify any single nucleotide polymorphisms (SNPs) that affected expression and ascertain the underlying mechanisms. Methods: After scanning TAPBP for common SNPs, rs111686073 (G/C) was identified as a variant found only in blacks that significantly correlated with expression via qPCR in two South African cohorts. To verify the effect on expression, constructs of different lengths were generated from the 5’ UTR of TAPBP and examined with luciferase assays in HeLa cells. Electrophoretic mobility shift assays were performed to determine if the transcription factors AP-2a or Sp1, predicted to bind by Alibaba2, mediated the change in expression. Results: The SNP rs111686073, located in the 5’ UTR, was found to cause significant changes in mRNA levels in two separate black cohorts (p = 0.002, 0.004; Figure 1A). Luciferase assays confirmed that the SNP altered expression with the G variant conferring higher expression than the C variant (p = 0.0004; Figure 1B). The SNP was found to be a binding site for the transcription factor AP-2a, which appears to increase expression (Figure 1C). Conclusion: The SNP rs111686073 is significantly associated with TAPBP expression, and the G variant results in increased expression over the C variant in luciferase assays, although AP-2a binds both. EMSA analysis indicates that

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CROI 2018