HIV-2 infection is characterized by low viremia and slow disease progression as compared to HIV-1 infection. Circulating CD14 ++ CD16 + monocytes were found to accumulate and CD11c + conventional dendritic cells (cDC) to be depleted in a Portuguese cohort of people living with HIV-2 (PLWHIV-2), compared to blood bank healthy donors (HD). We studied more precisely classical monocytes; CD16 + inflammatory (intermediate, non-classical and slan + monocytes, known to accumulate during viremic HIV-1 infection); cDC1, important for cross-presentation, and cDC2, both depleted during HIV-1 infection. We analyzed by flow cytometry these PBMC subsets from Paris area residents: 29 asymptomatic, untreated PLWHIV-2 from the IMMUNOVIR-2 study, part of the ANRS-CO5 HIV-2 cohort: 19 long-term non-progressors (LTNP; infection ≥8 years, undetectable viral load, stable CD4 counts≥500/µL; 17 of West-African origin-WA), and 10 non-LTNP (P; progressive infection; 9 WA); and 30 age-and sex-matched controls: 16 blood bank HD with unknown geographical origin, and 10 HD of WA origin (GeoHD). We measured plasma bacterial translocation markers by ELISA. Non-classical monocyte counts were higher in GeoHD than in HD (54 vs. 32 cells/µL, p = 0.0002). Slan + monocyte counts were twice as high in GeoHD than in HD (WA: 28 vs. 13 cells/µL, p = 0.0002). Thus cell counts were compared only between participants of WA origin. They were similar in LTNP, P and GeoHD, indicating that there were no HIV-2 related differences. cDC counts did not show major differences between the groups. Interestingly, inflammatory monocyte counts correlated with plasma sCD14 and LBP only in PLWHIV-2, especially LTNP, and not in GeoHD. In conclusion, in LTNP PLWHIV-2, inflammatory monocyte counts correlated with LBP or sCD14 plasma levels, indicating a potential innate immune response to subclinical bacterial translocation. As GeoHD had higher inflammatory monocyte counts than HD, our data also show that specific controls are important to refine innate immunity studies.

Human plasmacytoid dendritic cells (pDC) can cross-present antigens from apoptotic HIVinfected cells or tumor cells to CD8 + T cells. As pDC respond to HIV virions by maturing and secreting cytokines, we wondered whether these innate properties would affect crosspresentation from HIV-infected cells. We incubated purified blood DC with apoptotic HIVinfected H9 cells and then explored the activation process of HIV-specific cloned CD8 + T cells, in the presence of saquinavir We studied IFN-g secretion by HIV-specific T cells, which is known to be tightly regulated by engagement of the T cell receptor. We found that HIV-specific secretion by cloned HIV-specific CD8 + T cells was stimulated by pDC and cDC1 more than by cDC2, and was strictly MHC-Class I (MHC-I)-restricted. Surprisingly, intracellular production of IFN-γ was only partly MHC-I restricted for pDC, indicating a non-cognate CD8 + T cell activation. Plasmacytoid DC, but not cDC, matured and secreted IFN-a in the presence of apoptotic H9HIV cells. A cocktail of IFN-a, IFN-b and TNF-a induced intracellular production of IFN-γ but not Granzyme-B, mimicked the non-cognate mechanism, and neutralization of type I IFN signaling blocked non-cognate intracellular production of IFN-γ in the co-culture model. Moreover, cognate stimulation was required to induce IFN-γ secretion in addition to the cytokine cocktail. Thus, IFN-γ secretion is tightly regulated by engagement of the TCR as expected, but in the context of virus-infected cells, pDC can trigger intracellular IFN-γ accumulation in CD8 + T cells, potentializing IFN-γ secretion once CD8 + T cells make cognate interactions. These findings may help manipulate type I IFN signaling to enhance specifically antigen-specific CD8 + T cell activation against chronic infections or tumors. • HIV-infected H9 cells induce type I IFN production by pDC • Type I IFN induces IFN-γ but not Granzyme intracellular production in CD8 + T cells • pDC cross-present MHC-I-restricted HIV-Gag antigen to specific CD8 + T cells • IFN-γ secretion is potentiated by type I IFN, but only upon cognate interaction