Sex differences in the Toll-like receptor-mediated response of plasmacytoid dendritic cells to HIV-1

Abstract

Manifestations of viral infections can differ between women and men, and marked sex differences have been described in the course of HIV-1 disease. HIV-1-infected women tend to have lower viral loads early in HIV-1 infection but progress faster to AIDS for a given viral load than men. Here we show substantial sex differences in the response of plasmacytoid dendritic cells (pDCs) to HIV-1. pDCs derived from women produce markedly more interferon-alpha (IFN-alpha) in response to HIV-1-encoded Toll-like receptor 7 (TLR7) ligands than pDCs derived from men, resulting in stronger secondary activation of CD8(+) T cells. In line with these in vitro studies, treatment-naive women chronically infected with HIV-1 had considerably higher levels of CD8(+) T cell activation than men after adjusting for viral load. These data show that sex differences in TLR-mediated activation of pDCs may account for higher immune activation in women compared to men at a given HIV-1 viral load and provide a mechanism by which the same level of viral replication might result in faster HIV-1 disease progression in women compared to men. Modulation of the TLR7 pathway in pDCs may therefore represent a new approach to reduce HIV-1-associated pathology.

Figure 1

Sex differences in IFN-α production of pDC following TLR7/8 stimulation with HIV-1-derived ligands. (a) Representative flow plots demonstrating the IFN-α production by CD123⁺ pDCs derived from women (upper panel) and by CD123⁺ pDCs derived from men (lower panel) for unstimulated controls (left column), and following 20 h of stimulation with the HIV-1 derived TLR7/8 ligand Gag_RNA1166 (middle column) or the TLR9 ligand ODN2216 (right column) are shown. The percentage of IFN-α producing pDCs is shown in the upper right corner of each plot. (b) The percentage of IFN-α⁺ pDCs in men (shown in black, n = 20) as compared to women (shown in red, n = 23) following stimulation with the HIV-1-derived ssRNAs, Gag_RNA1166 and Gp160_RNA2093, or the TLR9 ligand ODN2216 are shown. (c) The percentage of IFN-α⁺ pDCs from men (shown in black, n = 19) and women (shown in red, n = 22) following stimulation with AT-2 inactivated HIV-1 virus (AT-2) or vesicle control (Ves) is shown. (d) Representative flow plots demonstrating the TNF-α production by CD123⁺ pDCs are shown. The percentage of TNF-α producing pDCs is shown in the upper right corner of each plot. (e) The percentage of TNF-α⁺ pDCs in men (shown in black, n = 20) and women (shown in red, n = 23) following stimulation with the HIV-1-derived ssRNAs, Gag_RNA1166 and Gp160_RNA2093, or ODN2216 are shown. All horizontal bars represent mean value for that sample group.

Figure 2

Impact of sex hormone levels on the IFN-α production by pDCs in response to TLR7/8 agonists. Plasma progesterone levels measured in 16 pre-menopausal women were significantly correlated to the percentage of IFN-α⁺ pDCs in response to stimulation with the HIV-1 derived TLR7/8 ligand Gag_RNA1166.

Figure 3

Sex differences in CD38 expression on CD8⁺ T cells following stimulation with HIV-1-derived TLR7/8 ligands is dependent on IFN-α (a) The percent CD38^high CD8⁺ T cells following 20 h of stimulation with HIV-1-derived TLR7/8 ligands (Gp160_RNA2093 and Gag_RNA1166), inactive control ssRNA (Gag_RNA1166A), AT-2 virus, or vesicle control for all individuals is shown. (b) Differences in the percent CD38^high CD8⁺ T cells from men (shown in black) and from women (shown in red) following 20 h of stimulation of PBMCs with the HIV-1 derived TLR7/8 ligands, Gp160_RNA2093 and GagRNA₁₁₆₆, inactive control ssRNA (Gag_RNA1166A), AT-2 virus, or vesicle control is shown. (c) The percentage of CD38^highCD8⁺ T cells above background in response to the TLR7 ligand CL097 was set to 100%, and the remaining activation in the presence of blocking antibodies against IFN-α receptors 1 and 2 is shown in the right column (CL097 + anti-IFNAR1/2). (d) Dose dependent increase in T cell activation as represented by percent of CD38^highCD8⁺ T cells was observed following stimulation of PBMCs from healthy donors with increasing amounts of human IFN-α ranging from 0–100 ng ml⁻¹. All horizontal bars represent mean value for that sample group.

Figure 4

Sex differences in the CD4⁺ and CD8⁺ T cell activation of HIV-1-infected, treatment-naïve individuals. The association between sex and the percentage of CD38⁺HLA-DR⁺CD4⁺ (a) or CD38⁺HLA-DR⁺CD8⁺ (b) T cells adjusting for HIV-1 viral load is shown. HIV-1 RNA load measured at baseline in women (open red symbol) and men (closed blue symbol) are correlated to CD4⁺ and CD8⁺ T cell activation (correlation for women shown with red dotted line and for men with blue solid line).