AN ANALYSIS OF CO-CIRCULATING SEROTYPES FOR BLUETONGUE-17 VIRULENCE MARKERS

We have recently identified two markers associated with virulent strai ns of bluetongue virus serotype 17.(1) These differences are an altere d 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 v irulence-associated markers may have been acquired by bluetongue-17 th rough genetic interaction with other circulating serotypes of the viru s. To test this hypothesis, we studied all isolates of other BLU serot ypes obtained from the same sentinel cattle herds in Central America a nd the Caribbean on the same days as BLU-17 isolates. We looked for ev idence of common epitopes on VP2 or an RNA segment 3 of identical mobi lity to that of the virulent strains of BLU-17. We found no evidence t o indicate that genetic interaction with other co-circulating serotype s gave rise to these two specific virulence-associated markers of BLU- 17.