Antigenic variation of the bovine ephemeral fever virus glycoprotein

Glycoprotein-specific monoclonal antibodies (MAbs) were used to select escape mutants of bovine ephemeral fever (BEF) virus to determine the escape frequency for different epitopes and to construct an epitope map. At least six antigenic sites were detected by this method and escape frequencies between 10(-2) and 10(-8) were recorded. One new non-conformational site was defined by a MAb, 5A5, which neutralized Berrimah and Kimberley viruses as well as three BEF virus strains. Batch to batch variation was detected in the BB7721 strain of BEF virus when tested for MAb neutralization. Eighteen strains of BEF virus, isolated from blood and insects from a variety of locations in Australia over a period of 33 years, were examined using MAbs and at least one epitope could not be detected in strains isolated since 1975. Implications for vaccine development are discussed.