Engulfment of apoptotic cells expressing HCV proteins leads to differential chemokine expression and STAT signaling in human dendritic cells

Abstract

In the majority of cases, infection with hepatitis C virus (HCV) becomes chronic and is often associated with impaired innate and adaptive immune responses. The mechanisms underlying viral persistence and lack of protective immunity are poorly understood. Considering that dendritic cells (DCs) play critical roles in initiating and modulating immune responses, we explored the effect of HCV proteins on DC gene and protein expression, phenotype, and function. Human DCs were generated following plastic adherence of monocytes and culture with granulocyte-macrophage colony-stimulating factor and interleukin-4 (IL-4) from normal subjects. Autologous nonadherent peripheral blood mononuclear cells were infected with vaccinia constructs expressing various HCV proteins (core-E1, NS5A, NS5B) or an irrelevant protein beta-galactosidase (beta-gal) as the control, induced to undergo apoptosis, then co-cultured with DCs. Between 2% and 10% of the genes probed in a cDNA nylon array were differentially regulated within DCs that had engulfed HCV proteins. In particular, the presence of intracellular NS5A led to increased transcriptional and protein expression of IL-8 (CXCL-8), a chemokine with proinflammatory and anti-interferon properties, and impaired interferon induction of signal transducers and activators of transcription 1 (STAT1) serine and tyrosine and STAT2 tyrosine phosphorylation. These data provide novel mechanisms by which HCV subverts antiviral host immunity.