Production of Interferon α by Human Immunodeficiency Virus Type 1 in Human Plasmacytoid Dendritic Cells Is Dependent on Induction of Autophagy

J Infect Dis. 2012 Apr 15;205(8):1258-67. doi: 10.1093/infdis/jis187. Epub 2012 Mar 6.

Abstract

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.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Autophagy / physiology*
  • Cells, Cultured
  • Dendritic Cells / metabolism*
  • Dendritic Cells / virology*
  • Gene Expression Regulation
  • HIV-1 / physiology*
  • Humans
  • Immunosuppressive Agents / pharmacology
  • Interferon Regulatory Factor-7 / genetics
  • Interferon Regulatory Factor-7 / metabolism
  • Interferon-alpha / metabolism*
  • RNA Interference
  • RNA, Small Interfering
  • Sirolimus / pharmacology
  • TOR Serine-Threonine Kinases / genetics
  • TOR Serine-Threonine Kinases / metabolism
  • Toll-Like Receptor 7 / genetics
  • Toll-Like Receptor 7 / metabolism

Substances

  • Immunosuppressive Agents
  • Interferon Regulatory Factor-7
  • Interferon-alpha
  • RNA, Small Interfering
  • TLR7 protein, human
  • Toll-Like Receptor 7
  • MTOR protein, human
  • TOR Serine-Threonine Kinases
  • Sirolimus