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Nucleic acid was extracted from purified hepatitis A virus, radiolabeled with 125I, and shown to consist of single-stranded RNA which sediments at 35S and contains sequences of polyadenylic acid. These findings are consistent with hepatitis A virus being a member of the genus Enterovirus within the family Picornaviridae.

When hepatitis A virus was inoculated into Vero cells, virus-specified protein and RNA synthesis was detected. Production of viral protein was detected by electrophoretic analysis in polyacrylamide gels by using a double-label coelectrophoresis and subtraction method which eliminated the contribution of host protein components from the profiles of virus-infected cytoplasm. Eleven virus-specified proteins were detected in the net electrophoretic profiles of hepatitis A virus-infected cells. The molecular weights of these proteins were very similar to those detected in cells infected with poliovirus type 1. Virus-specified protein synthesis could be detected at 3 to 6 h and continued for at least 48 h postinfection, but no significant effect on host-cell macromolecular synthesis was observed. Limited viral RNA replication occurred between 2 and 6 h postinfection. The genomic RNA of hepatitis A virus was extracted and shown to be capable of infecting cells and inducing the same set of proteins as intact virus, indicating that the RNA genome is positive stranded. Progeny virus was never detected in the supernatant fluids of infected cell cultures, and the cells showed no observable cytopathology, even though hepatitis A virus-specific proteins and antigens were being produced. The nature of the defect in the replicative cycle of hepatitis A virus in this system remains unknown.

Human hepatitis A virus (HAV) was propagated in primary African Green Monkey (Cercopithecus aethiops) kidney (AGMK) cell cultures. Three strains of HAV were used: MS-1, SD-11, and HM-175. Cells were inoculated with marmoset-passaged material or human clinical specimens and were stained by direct immunofluorescence to establish the identity of the virus. Both clinical samples and marmoset-passaged material produced immunofluorescence. HAV antigen was found scattered throughout the cytoplasm of inoculated cultures. The HM-175 strain produced the most intense immunofluorescence. This strain of HAV had been serially passaged in cell culture seven times. Blocking experiments with paired human sera from naturally acquired HAV infections and hyperimmune chimpanzee serum from an experimentally infected animal established that the immunofluorescence was specific. The viral antigen was found to be exclusively intracellular. The interval to maximum HAV antigen expression was decreased by serial passage. The HAV strain described herein, which was recovered directly from the stool specimen of a patient with HAV in primary AGMK cell culture, may prove useful as a source of antigen for serological tests and as a candidate vaccine strain.

A batch of 984 sera obtained from a stratified sample of Melanesians and Indians living in rural and urban areas of Fiji in 1981 were for hepatitis B surface antigen (HBsAg) and antibody to hepatitis B core antigen (anti-HBc) by solid phase radioimmunoassay. The prevalence of hepatitis B infection (as measured by the sum of HBsAg and anti-HBc frequencies of HBsAg negative sera in the two groups) was 81.5% and 17.9%, respectively. No major differences were detected between urban and rural populations. While hepatitis B virus is endemic in Melanesians and Indians, the epidemiology of the infection shows certain differences. Among Melanesians, infection appears to be acquired early in life and peak prevalence of serologic markers of infection occurs during the second decade. Among the Indian population, the prevalence of markers increases steadily with age, presumably as a result of continuous exposure and infection throughout life. the high prevalence of infection and carriers among Melanesians is consistent with previous observations among Pacific populations. The lower prevalence of infection among Indians is remarkable, since they constitute almost half of the total population and live under similar conditions. Since the two populations remain largely separate in terms of housing and schooling, and intermarriage is uncommon, it is no possible to determine whether these differences merely represent different degrees of exposure to the virus or are the reflection of differences in susceptibility or response to infection.

This report compares two assay systems for monitoring human immunodeficiency virus (HIV) replication in peripheral blood leukocyte cultures. A commercial enzyme-linked immunoassay detected core antigen (p24) in 80% of cell cultures from HIV-seropositive individuals, whereas 67% of the cell cultures produced detectable levels of reverse transcriptase activity. There were clearly three patterns of reverse transcriptase activity produced, two of which may evade detection without regular sampling and maintaining cell cultures for more than 4 weeks. Once established, core antigen levels remained high so that cell cultures could be confidently monitored by an intermittent screening regimen.