HCV infection by cell-to-cell transmission: choice or necessity?

In vitro models of HCV infection have allowed for the clarifying of molecules and mechanisms involved in the main steps of virus cell-entry. HCV entry and neutralization appear to be closely related. Neutralizing antibodies inhibit the E2-CD81 binding, therefore CD81 is considered to be a major target of immune response. The tight-junction proteins are also implicated in E2-binding to CD81 and successive steps of virus entry, in cooperation with several co-receptors, whose involvement has still to be elucidated. Increasing evidence has emphasized the importance of cell-to-cell HCV-transmission in chronic infection. This route for infection could favour virus-escape from host-neutralization though its CD81-dependency is still debated. The main reasons which have delayed our understanding of HCV-infection are here critically reviewed, as are the challenges faced by investigators in the field. A deeper insight into the different pathways involved could help to elucidate some crucial features of HCV infection mechanisms and disclose important implications in its pathogenesis, which could help in suggesting new targets for successful immune-prophylactic/therapeutic strategies.