Comparison of two defective hepatitis A virus strains adapted to cell cultures.

The replication of two defective hepatitis A virus strains in cell culture was examined. The w.t. HAS-15 strain growing in FRhK-4 cells produced infectious icosahedral virions 27 nm in size as well as round shaped particles with lipids attached to their surface. The morphogenesis of HAV was membrane-dependent and the detected particles were in various degree of maturation. The MBB 11/5 strain growing in PLC/PRF/5 cells produced mainly noninfectious empty procapsids without RNA genome. The translation of viral proteins was uninhibited in both strains. The reason for restricted replication competence of both strains seemed to be different. In HAS-15, highly efficient encapsidation of the progeny RNA positive-strand lowered the formation of replicative intermediate forms. In MBB 11/5, nearly exclusive empty procapsid production gave evidence for the failure of the VPg primer protein attachment to viral RNA. Changes in the efficacy of viral genome replication were a result of the adaptation of HAV to propagation in vitro.