Our results show that HIV-specific

CD8+ T cells contribute significantly to IL-10 production in the peripheral blood and that this subset modulates monocyte activation. Constitutive IL-10 gene transcription was reported to be upregulated in multiple cell subsets among PBMCs in chronically HIV-infected individuals but there is uncertainty as to whether this is universally reflected in increased spontaneous or antigen-driven cytokine production [7]. We therefore analysed the Obeticholic Acid cell line fractions of IL-10-producing cells among circulating CD4+ T cells, CD8+ T cells, CD19+ B cells and CD14+ monocytes ex vivo, after stimulation with either 0.05% DMSO or HIV-1 gag peptides, in three subject

groups: patients who were antiretroviral (ART) naïve (n = 31, median viral load – 17 964 copies/mL) or fully suppressed on ART for >1 year (n = 20) and HIV-uninfected healthy controls (n = 5). Study participants’ characteristics are described in Table 1. The gating strategy used to identify IL-10-producing cells is shown in Supporting Information Fig. 1. Constitutive IL-10 release (0.05% DMSO control) was detected in all cell subsets analysed; the proportion of IL-10-producing cells was highest among CD19+ B cells and CD14+ Caspases apoptosis monocytes in all three groups but there were no significant differences among the groups for each cell subset analysed, suggesting that constitutive IL-10 expression was not increased at the protein level in this patient cohort

(Supporting Information Fig. 2). By contrast, we observed significant IL-10 secretion in response to HIV-1 gag stimulation, predominantly in CD8+ T cells. These IL-10+ CD8+ T cells were rare but reproducibly detected in ART-naïve viraemic individuals, at a median frequency of 0.01% (range 0–0.13%, tenfold greater than the 0.05% DMSO control). Frequencies among ART-treated and uninfected most subjects were <0.001 and 0%, respectively (p < 0.01, Fig. 1A and B). Although the proportion of IL-10+ cells was lower among CD8+ T cells than monocytes, CD8+ T cells were the major contributors to IL-10 production in response to HIV-1 gag, due to the higher absolute numbers of CD8+ T cells in the peripheral blood (Fig. 1C). Phenotypic analysis of HIV-specific IL-10+ CD8+ T cells revealed that the majority were CD25- and FoxP3-negative and a substantial minority expressed CXCR3, a ligand for inflammatory chemokines that promotes migration to sites of inflammation and differentiation towards an effector phenotype [15] (Fig. 1D). We also investigated the expression of the gut-homing integrin alpha-4/beta-7 on HIV-specific IL-10+ CD8+ T cells, since IL-10 expression is upregulated in gut-associated lymphoid tissue (GALT) during acute HIV-1 infection [16].