Hybridization relatedness of Israeli and U.S. bluetongue (BLU) serotypes using cDNA probes from BLU virus strain 11-UC8.

Partial cDNA clones representing 47%, 96%, and 98% of genome segments 7, 9, and 10, respectively, of a US bluetongue virus (BLU) 11 virulent strain were used to study, for the first time, the genetic relationships between Israeli BLU proto-serotypes and field isolates, and US BLU proto-serotypes. Their usefulness as group-specific identification probes was also determined. The viral nucleic acid was extracted from the infected cells and the purified dsRNA genome segments were fractionated by polyacrylamide gel electrophoresis, transferred to a nylon membrane and hybridized to the 32P labeled DNA probes. The three probes recognized all the samples tested. Genome segment 7, that code for the mayor inner capsid protein VP7, showed the most variation in the hybridization signal with the US proto-serotypes and all the Israeli samples studied. The genome segments 9 and 10 that code for the minor inner capsid protein VP6 and the nonstructural protein NS3, respectively, were highly conserved in all the samples tested despite their distant geographical regions of origin. The last two mentioned clones showed to be good group-specific probes for the identification of BLU samples from Israel and United States. The obtained cloned genetic probes were also tested against US epizootic haemorrhagic disease virus (EHDV) serotype 1 and 2 viral dsRNA, a distantly related orbivirus. None of them hybridized with the viral dsRNA of these two viruses.