Fast growth of a Brazilian hepatitis A virus (HAF-203) in a primate cell line.

A hepatitis A virus (HAV, HAF-203) isolated in Brazil was submitted to 8 serial passages through fetal Rhesus kidney cells (FRhK-4). The kinetics of replication were monitored by enzyme immunoassay (EIA-HAVAg) and cDNA-RNA dot blot hybridization. The maximum level of RNA, which was observed 21 days post-infection (p.i.) during the 3rd passage, when HAVAg was still undetectable by EIA, served as a basis to establish subsequent passages every 21 days p.i. This schedule of passage resulted in a progressive reduction of time between culture infection and HAVAg and RNA production, together with an enhancement in antigen titer content of cell lysates. During the 7th passage, maximum HAVAg and RNA levels were detected at 7 days. Fourteen days after the 8th passage, clear morphological modifications appeared, suggesting a good adaptation of HAF-203 to FRhK-4 cells. Obtaining a fast-growing Brazilian HAV is very important for the development of vaccines.