DC contact with HIV-1-infected cells leads to high levels of Env-mediated virion endocytosis coupled with enhanced HIV-1 Ag presentation.

In HIV-infected patients, DC are likely to interact with both cell-free HIV and HIV-infected cells. We were interested in investigating the mechanism of virus transmission occurring upon contact between HIV-1-infected cells and DC, as well as the consequences for HIV-1 Ag-presenting activity. By comparing mixed co-cultures with trans-well cultures, we observed that cell-to-cell contact strongly increased HIV-1 Env-mediated virion endocytosis in target DC. This endocytosis was independent of HIV-1 tropism, de novo infection, HIV-1 Env-CD4-dependent fusion, and immature DC activation/maturation. We also found that augmentation of HIV-1 endocytosis was closely correlated with strong, Env-dependent HIV-1 Ag presentation by DC. Our results provide a better understanding of the mechanisms underlying the induction of the anti-HIV adaptive immune response.