Propagation of hepatitis A virus in human diploid fibroblast cells

Human hepatitis A virus (HAV) was propagated in human diploid fibroblast cultures (2BS cells) in vitro. Replication of the virus was followed by immunofluorescent staining (IF), indirect ELISA, and by immune electron microscopy. When 2BS cells were inoculated with faecal extracts containing HAV, synthesis of hepatitis A antigen (HAAg) could be detected in the cytoplasm by IF. Its concentration reached a maximum at four weeks post-inoculation. Measured by solid-phase indirect ELISA, the positive/negative (P/N) ratio for HAAg reached values of up to 7.7. The identity of newly synthesized virus particles with HAV was established by immune electron microscopy, IF-blocking, and neutralization with human convalescent serum. Infected cells showed no signs of a specific cytopathic effect. Two of the virus strains propagated in 2BS cells may prove useful as a source of antigen for serologic tests; one of them might be a candidate strain for HAV vaccine.

Etiologic and serologic investigations of the 1980 epidemic of dengue fever on Hainan Island, China

Virologic and seroepidemiologic studies were carried out during an epidemic of dengue fever on Hainan Island in 1980. Dengue 3 virus was isolated from 46 of 77 acute phase sera and from 1 of 10 pools of adult Aedes aegypti. Dengue 1 virus virus was isolated from a single acute phase serum. Seroepidemiologic investigations showed that 74% of healthy individuals in the epidemic area had antibody to dengue virus compared to 54% in an area where epidemic dengue had occurred in 1978, and less than or equal to 8% in nonepidemic areas. There were no significant differences in antibody prevalence for different sex and age groups.