Sterol metabolism modulates susceptibility to HIV-1 Infection

Background: 25-hydroxylase (CH25H) is an Interferon stimulated gene (ISG), which catalyzes the synthesis of 25-Hydroxycholesterol (25HC). 25HC intervenes in metabolic and infectious processes as controls cholesterol homeostasis and influences viral entry into host cells.We verified whether natural resistance to HIV-1 infection in HIV-1-exposed seronegative (HESN) individuals is at least partially mediated by particularities in sterol biosynthesis. Methods: Peripheral blood mononuclear cells (PBMCs) and monocyte-derived macrophages (MDMs) isolated from 15 sexually-exposed HESN and 15 healthy controls (HC) were in vitro HIV-1-infected and analyzed for: 1) percentage of IFN\u3b1-producing plasmacytoid Dendritic Cells (pDCs); 2) Cholesterol signaling and inflammatory response RNA expression; 3) resistance to HIV-1 infection. MDMs from 5 HC were in vitro HIV-1-infected in the absence/presence of exogenously added 25HC. Results: IFN\u3b1-producing pDCs were augmented in HESN compared to HCs both in unstimulated and in in vitro HIV-1-infected PBMCs (p<0.001). An increased expression of CH25H and of a number of genes involved in cholesterol metabolism (ABCA1, ABCG1, CYP7B1, LXR\u3b1, OSBP, PPAR\u3b3, SCARB1) was observed as well; this, was associated with a reduced susceptibility to in vitro HIV-1-infection of PBMCs and MDMs (p<0.01). Notably, addition of 25HC to MDMs resulted in increased cholesterol efflux and augmented resistance to in vitro HIV-1-infection. Conclusions: Results herein show that in HESN sterol metabolism might be particularly efficient. This could be related to the activation of the IFN\u3b1 pathway and results into a reduced susceptibility to in vitro HIV-1 infection. These results suggest a possible basis for therapeutic interventions to modulate HIV-1 infection