Propagation of hepatitis A virus in human diploid fibroblast cells. 
Human hepatitis A virus (HAV) was propagated in human diploid fibroblast cultures (2BS cells) in vitro.  Replication of the virus was followed by immunofluorescent staining (IF), indirect ELISA, and by immune electron microscopy.  When 2BS cells were inoculated with faecal extracts containing HAV, synthesis of hepatitis A antigen (HAAg) could be detected in the cytoplasm by IF.  Its concentration reached a maximum at four weeks post-inoculation.  Measured by solid-phase indirect ELISA, the positive/negative (P/N) ratio for HAAg reached values of up to 7.7.  The identity of newly synthesized virus particles with HAV was established by immune electron microscopy, IF-blocking, and neutralization with human convalescent serum.  Infected cells showed no signs of a specific cytopathic effect.  Two of the virus strains propagated in 2BS cells may prove useful as a source of antigen for serologic tests; one of them might be a candidate strain for HAV vaccine.