UTILIZATION OF CHIMERAS BETWEEN HUMAN (HM-175) AND SIMIAN (AGM-27) STRAINS OF HEPATITIS-A VIRUS TO STUDY THE MOLECULAR-BASIS OF VIRULENCE

Chimeras between human (HM-175) and simian (AGM-27) strains of hepatit is A virus (HAV) were constructed to evaluate the effect of the 2C gen e of AGM-27 on HAV replication in cell culture and virulence in tamari ns (Saguinus mystax) and chimpanzees (Pan troglodytes). Kinetic studie s and radioimmunofocus assays demonstrated that replacement of the 2C gene of HAV/7, a cell culture-adapted strain of HM-175, with that of A GM-27 drastically reduced the ability of the virus to replicate in cul tured cells. Intragenic chimeras containing AGM-27 sequences in either the 5' or 3' half of the 2C gene replicated in cell culture at an int ermediate level. Whereas HAV/7 is attenuated for tamarins, a chimera c ontaining the simian virus 2C gene in the HAV/7 background was virulen t in tamarins, demonstrating that the simian virus 2C gene alone can c onfer the phenotype of virulence to an otherwise attenuated virus. Clu sters of AGM-27-specific residues near both ends of the 2C protein wer e required for virulence since a chimera containing AGM-27 sequences i n the carboxyterminal half of 2C was partially attenuated for tamarins while one containing AGM-27 sequences only in the amino-terminal half of 2C was even more attenuated. Chimeras containing either the entire or only the 3' half of the simian virus 2C gene in the HAV/7 backgrou nd were attenuated for chimpanzees.