APOE and infection: To examine whether Erns of pestivirus can compensate for the role of apolipoproteins in the formation of infectious HCV particles, ApoE or HA-tagged Erns (HA-Erns) was lentivirally expressed in BE-KO cells and intracellular HCV RNA and infectious viral titers in the supernatants were determined at 72-h post-infection with HCV (Fig 1A–1D).