Binding of HCV E2 to CD81 induces RANTES secretion and internalization of CC chemokine receptor 5

Hepatitis C virus (HCV) infection has been shown to be associated with reduced expression of the CC chemokine receptor (CCR) 5, and reduced responsiveness of lymphocytes to chemokines. However, the mechanism by which HCV alters CCR5 expression remains unclear. Here, we investigated whether altered CCR5 expression in hepatitis C results from interactions of CD81 with the HCV E2 protein. Peripheral blood mononuclear cells (PBMC) from HCV-negative individuals were prepared by Ficoll density gradient separation. PBMC subpopulations (CD4+, CD8+ lymphocytes, CD19+ B cells, natural killer (NK) cells and monocyte-derived dendritic cells) were isolated and stimulated with immobilized HCV E2, and changes in CCR5 expression and CC-chemokine secretion were determined. Migration assays were performed using a 5-microm nitrocellulose filter microchamber system according to the manufacturer's recommendations. Exposure of PBMC to HCV E2 induced a dose-dependent release of regulated on activation normal T-cell-expressed and secreted (RANTES), down-regulation of CCR5 expression and intracellular accumulation of CCR5. This effect was blocked by preincubation of PBMC with anti-CD81. RANTES release following exposure to HCV E2 was mainly attributable to CD8+ cells. After exposure to HCV E2 markedly fewer CD8-positive lymphocytes were attracted by RANTES when compared with CD8+ cells that were studied in the absence of HCV E2. Our results suggest that interaction of HCV E2 with CD81 leads to increased RANTES secretion by CD8+ lymphocytes which induces down-regulation of CCR5 surface via receptor internalization resulting in altered lymphocyte migration.