Fig. 4.

Processing of HBV particles by endosomal lysate enables infection of nonpermissive cells. (A) Confocal microscopy of Huh7 cells infected with unprocessed HBV particles (Left) or with particles incubated with endosomal lysate from HepG2 cells for 30 min before infection (Right). The MGE in both cases was 10³. For analysis of the infectivity, HBsAg- and HBcAg-specific antisera were used. Their antigen-specific binding was detected by secondary antibodies visualized by red and blue fluorescence, respectively. Actin filaments were stained by using FITC-conjugated phalloidine. Photographs were taken at ×200 and ×630 magnification. (B) Confocal microscopy of LMH cells infected with unprocessed DHBV particles or with processed WT DHBV, DHBVD1/2, and DHBVD2 particles that had been preincubated with endosomal lysates from LMH cells for 60 min. As a control, processing of WT DHBV was performed in the presence of a protease inhibitor mixture (Roche). The MGE in all cases was 10³. For analysis of the infectivity, a surface-specific serum visualized by the blue fluorescence was used. Photographs were taken at ×630 magnification.