Production of interferon α by human immunodeficiency virus type 1 in human plasmacytoid dendritic cells is dependent on induction of autophagy

Background: The mechanisms responsible for interferon α (IFN-α) production by plasmacytoid dendritic cells (pDCs) during human immunodeficiency virus type 1 (HIV-1) Infection are unknown. This research examined the roles of Toll-like Receptor 7 (TLR7) and Autophagy in IFN-α production by pDCs during HIV-1 Infection.

Methods: pDCs from human peripheral blood mononuclear cells were incubated with infectious or aldrithiol 2 (AT-2)-inactivated HIV-1 or with uridine-rich single-stranded RNA40 (ssRNA40) from the HIV-1 long terminal repeat. IFN-α was quantified by enzyme-linked immunosorbant assay. Autophagic proteins were detected by Western blot, and autophagosomes were identified using immunofluorescent and confocal microscopy. To inhibit Autophagy, pDCs were treated with the phosphoinositide-3 kinase inhibitor 3-methyladenine (3-MA) or were transfected with autophagy-related protein 7 or TLR7 small interfering RNA (siRNA).

Results: Increased levels of IFN-α were present in culture supernatants following 16-hour incubation of pDCs with infectious or AT-2-inactivated HIV-1. Treatment of pDCs with ssRNA40 but not ssRNA41 resulted in high levels of IFN-α. pDCs exposed to HIV-1 gp120, rapamycin, or 3-MA alone failed to induce IFN-α. Pretreatment of pDCs with 3-MA significantly reduced the induction of IFN-α by ssRNA40. Similarly, knock down of autophagy-related protein 7 and TLR7 by use of siRNA significantly reduced the induction of IFN-α by ssRNA40 or HIV-1.

Conclusions: These findings demonstrate that IFN-α production by pDCs exposed to infectious or noninfectious HIV-1 and ssRNA40 occurs through induction of Autophagy following TLR7 signaling.