Hepatitis C Virus Entry into Macrophages/Monocytes Mainly Depends on the Phagocytosis of Macrophages.

BACKGROUND: Hepatitis C virus (HCV) has been classified as a strictly hepatotropic pathogen for a long time, and hepatocytes are target cells for HCV infection. More and more studies showed non-liver cells supported HCV entry and replication, such as macrophages. The mechanisms of HCV entry into macrophages are still not clear. AIMS: This study aims to determine the way of HCV entry into macrophages. METHODS: Cell culture-derived infectious HCV particles (HCVcc) were prepared using Huh7 cells transfected with HCV RNA. CD81-knockdown cells were obtained through siRNA transfection. HCV RNA levels were determined by RT-qPCR. Flow cytometry analyses were used to determine cell surface levels of CD11b, CD68, and CD81. ELISA and western blotting were performed to quantify the protein levels of IL-1β, IL-6, and TNF-α. Phagocytic ability was determined by neutral red uptake assay. RESULTS: CD81 knockdown could not inhibit HCVcc entry into macrophages. The entry of HCV into macrophages could not be blocked by pooled IgG from chronic hepatitis C patient's sera. Macrophages derived from THP-1 cells displayed stronger phagocytic capacity, which also swallowed more HCV RNA. Treatment of macrophages with endocytic inhibitor, methyl-β-cyclodextrin, decreased the internalization of HCV. HCV uptake by macrophages was related to the reorganization of F-actin cytoskeleton and PI3Ks activation. HCV infection significantly increased the expression of IL1β and IL6 in macrophages and promoted apoptosis of macrophages. CONCLUSIONS: HCV entry into macrophages mainly depends on phagocytosis of macrophages.