Intra- and inter-serogroup genetic relatedness of orbiviruses. I. Blot hybridization of viruses of Australian serogroups.

Viruses in the Eubenangee, Wallal and Warrego serogroups of orbiviruses have been isolated primarily in Australia. Several isolates in these three serogroups were examined by gel electrophoresis and blot hybridization of genomic RNA. Conserved and variant genes were identified by the degree of hybridization between cognate genes. The dsRNA profiles of isolates within a serogroup exhibited heterogeneity in polyacrylamide gels, but they were indistinguishable in agarose gels. Isolates within a serogroup generally showed a high level of cross-hybridization in eight segments with cognate segments 2 and 6 exhibiting hybridization signal variants. Although Pata virus has been classified in the Eubenangee serogroup, it was not closely related to other Eubenangee isolates by hybridization. Similarly, Mitchell River virus was not closely related to other members of the Warrego serogroup. The taxonomic status of Pata and Mitchell River viruses should be reviewed, and in the interim they should be placed in the ungrouped set of orbiviruses. Inter-serogroup relatedness was also examined by blot hybridization. Representatives from the Eubenangee, Wallal, Warrego, bluetongue, epizootic haemorrhagic disease and Corriparta serogroups were examined. Several of the serogroups were distantly related, and the low level of relatedness was suggestive of a common ancestry. While many of these serogroups may co-circulate in nature, these data suggest that each serogroup represents a distinct gene pool. The taxonomic significance of these data is discussed.