Propagation of human hepatitis A virus in conventional cell lines

Fecal extracts of hepatitis A (HA) patients were selected for the presence of hepatitis A virus (HAV) by radioimmunoassay (RIA) and immune electron microscopy (IEM). When FL and Vero cells were inoculated with fecal extracts containing HAV, development of hepatitis A antigen (HAAg) was evident in the cytoplasm of the two cell lines by the indirect immunofluorescence (IF) test. The antigen was detectable in the cells 12 hr postinoculation (pi), and reached a plateau within two days pi. FL cell cultures inoculated with a specimen containing HAV were harvested and passaged four times. During the passages, efficient production of HAAg was confirmed in the infected cultures by three different serological tests: The indirect IF test, RIA using fixed cells, and RIA by the sandwich method. At the second and fourth passages, HAV particles were recovered in abundance from infected FL cell cultures by IEM. Throughout these experiments, no cytopathic effect (CPE) was discernible in the cultures.