Cultivation and characterization of rotavirus strains infecting newborn babies in Melbourne, Australia, from 1975 to 1979.

Twenty-three rotavirus strains obtained from the stools of 71 newborn babies were adapted to growth in MA-104 cells. Babies were housed in newborn nurseries of eight different obstetric hospitals in Melbourne between 1975 and 1979. All strains belonged to serotype 3 when reacted with serotype-specific neutralizing monoclonal antibodies in an enzyme immunoassay. Genome RNA of these 23 strains and of one stool virus not adapted to cell culture were compared by coelectrophoresis of mixtures of RNA. When strains were compared by coelectrophoresis of RNA for 4 h at 40 mA current, the majority appeared to be identical. Coelectrophoresis at 4 degrees C for 17 h at 10 mA current with 0.75-mm-thick polyacrylamide gels resulted in increased resolution of segments, revealing more genetic diversity than previously observed. Seventeen different electropherotypes showing slight variations in migration of one to seven segments were identified. Segments 5 and 7, 8, 9, 10, and 11 varied more frequently than segments 1, 2, 3, 4, and 6. Strains endemic in one hospital from 1975 to 1983 showed increased numbers of segmental changes over time. Differing patterns of reaction with two neutralizing monoclonal antibodies reacting with VP3 and VP7 were observed. Comparison of electropherotypes of three neonatal strains with a serotype 3 community strain showed marked differences in segment migration. The serotypic similarity, electropherotypic dissimilarity from community strains, and asymptomatic nature of most infections are additional evidence that these viruses infecting newborn babies form a unique group of rotaviruses.