An analysis of co-circulating serotypes for bluetongue-17 virulence markers.

We have recently identified two markers associated with virulent strains of bluetongue virus serotype 17. These differences are an altered antigenic structure of the outer capsid protein VP2 and an increased electrophoretic mobility of the RNA segment 3 that codes for an inner core protein. We did not observe these markers in confirmed avirulent strains of bluetongue virus serotype 17. We hypothesized that these virulence-associated markers may have been acquired by bluetongue-17 through genetic interaction with other circulating serotypes of the virus. To test this hypothesis, we studied all isolates of other BLU serotypes obtained from the same sentinel cattle herds in Central America and the Caribbean on the same days as BLU-17 isolates. We looked for evidence of common epitopes on VP2 or an RNA segment 3 of identical mobility to that of the virulent strains of BLU-17. We found no evidence to indicate that genetic interaction with other co-circulating serotypes gave rise to these two specific virulence-associated markers of BLU-17.