Two Electropherotypes of Bluetongue Virus Serotype 2 from Naturally Infected Calves

Abstract

SUMMARYThe first isolation of bluetongue virus (BTV) serotype 2 in the U.S.A. was in 1982 from a sentinel herd of cattle at Ona, Florida. Electrophoretic analysis of genome RNA revealed that all 16 serotype 2 isolates obtained from this focus of infection had one of two electropherotypes (designated Ona A and Ona B). All genome segments of Ona A and Ona B had detectable differences in electrophoretic mobility, with major differences noted for segments 1, 4, 5, 7, 8, 9 and 10. Electrophoretic comparison revealed that Ona A was indistinguishable from the African serotype 2 prototype isolated 23 years earlier. In 1983, Ona B, in the apparent absence of Ona A, was isolated from two additional cattle herds in Florida. These results suggest that Ona B may be a variant of Ona A that evolved as a result of mutation or reassortment with another BTV strain, and may be better adapted to the selective pressures found in southern Florida.Comparison of the electropherotypes of Ona B with two Florida isolates of serotype 13 and 17 and the prototypes of BTV 10, 11, 13 or 17 produced no evidence for reassortment between Ona A and any of these strains as the possible origin of Ona B.

Genotypic Transitions among Bluetongue Viral Isolates from Domestic Ruminants in Colorado during 1981–1984

“…The RNA segments were detected by silver staining. 3 Comparative SDS-PAGE analysis of viral proteins. Proteins were compared by SDS-PAGE to determine if differences in the electrophoretic mobility of translation products of the double-banded genome segments were detectable.…”

“…Viral RNA was extracted from BTV-infected BHK-21 cells using phenol in sodium acetate buffer, pH 5. 3 The electropherotype of each isolate was determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) on 10% gels. 3,13 As a reference electropherotype, genomic RNA from the US prototype of BTV 11 was coelectrophoresed in lanes adjacent to each RNA sample.…”

“…20 Serological data have been expanded by genomic analysis of BTV isolates. 3,8,12,18 Genomic variation among naturally occurring BTV, as with other members of the family Reoviridae, has been demonstrated by electrophoretic separation of the 10 double-stranded RNA genomic segments. Concurrent polypeptide analysis has also established translational significance of observed genomic differences.…”

“…3 It has been shown that viral strains of a single serotype, exhibiting more than 1 electropherotype, may coexist within a single animal or herd. 3,16 In addition, predominant electropherotypes have been shown to change during the course of a single bluetongue outbreak. 3 We report here the genetic transitions of BTV Received for publication May 20, 1988. infecting domestic ruminants in eastern Colorado over a 4-year period and the continued predominance of an electropherotype apparently resulting from multiple infections.…”

“…Concurrent polypeptide analysis has also established translational significance of observed genomic differences. 3 It has been shown that viral strains of a single serotype, exhibiting more than 1 electropherotype, may coexist within a single animal or herd. 3,16 In addition, predominant electropherotypes have been shown to change during the course of a single bluetongue outbreak.…”