Abstract Body

Background: Central and transitional memory CD4 Tcell maturation subsets comprise the largest fraction of the HIV reservoir in peripheral blood but less is known about the cellular composition of HIV reservoirs in those lymphoid tissues that disproportionately harbor HIV during suppressive ART. Methodology: 8 subjects on ART (5 started treatment during chronic infection, 3 during early infection, ART duration >3years, VL<50c/ml, CD4>350) underwent leukapheresis, lymph node biopsy and rectal biopsy. Following cell isolation, flow-based sorting was used to isolate naive (Nv), central- (CM), transitional- (TM) and effector- (EM) memory populations. Cellular HIV DNA and RNA were measured using previously published real time PCR assays and were normalized by simultaneous measurement of TERT and GAPDH, respectively. Infection frequencies and HIV expression was compared among sites and Tcell subsets. Results: HIV DNA was measurable from a majority of CD4 T cell maturation subsets from all three sites. The highest HIV DNA concentrations were in EM cells in rectum (median 2289 [IQR 1269-6424] c/106, p=0.008 for comparison with concentrations in EM, TM and CM from blood). HIV DNA levels in TM/CM cells in rectum were also higher than in CM or TM (p=0.016) and EM (p=0.16) in blood. HIV+ cell concentrations were intermediate for T cell subsets in lymph node. As expected, Nv cells had low infection frequencies. Paradoxically, HIV expression per infected cell (expressed as ratio of HIV RNA to DNA) was lower in all subsets in rectum compared to blood; expression levels were intermediate in lymph node cells. The contribution of each T cell subset to the total HIV reservoir differed strikingly by site. Infected EM cells comprised 80% of the total T cell reservoir in rectum, 40% of the reservoir in lymph node but <20% in blood. With the caveat of a small study size, infection frequencies tended to be lower in early treatment subjects compared to chronic treatment subjects while the distribution of infection among T cell subsets were not appreciably different between subject groups. Conclusions: The distribution of the reservoir is tissue dependent, with rectal tissues notable for a high frequency of HIV DNA in EM cells, but low levels of HIV RNA expression in these and other memory cells. The majority of the infected cells in rectum and ai sizable minority of infected cells in lymph node are found in EM cells, while most of the infected cells in blood are in CM/TM cells. These data suggest that the local host environment affects HIV expression and how latently infected cells take up residence. The impact of potentially curative interventions on HIV persistence is expected to be different across anatomic sites.