Identification of native foot-and-mouth disease virus non-structural protein 2C as a serological indicator to differentiate infected from vaccinated livestock.

Cattle and pigs which have been vaccinated against foot-and-mouth disease can be distinguished from convalescent animals by radio-immunoprecipitation and sodium dodecyl sulphate polyacrylamide gel electrophoresis of the virus-induced proteins reacting with the respective sera. Baby hamster kidney cells infected with foot-and-mouth disease virus (FMDV) (serotype A24) were labelled with 35S-methionine and the virus-induced proteins were precipitated with sera from vaccinated and subsequently challenged animals, convalescent animals retained for over 300 days, animals vaccinated or infected with viruses belonging to all serotypes of FMDV, and animals infected with encephalomyocarditis (EMC) or porcine or bovine enteroviruses. In addition to the structural proteins of the virus, the non-structural proteins 2C, 3ABC, 3C, 3CD and 3D were precipitated by convalescent sera, but only 3D was precipitated by serum from vaccinated animals. Proteins L, 2C and 3C were precipitated only after challenge with a heterotypic virus (serotype O1 Tunisia), indicating that virus replication of the challenge virus had taken place. No precipitation was detected with sera from EMC or enterovirus-infected animals. The results indicate that protein 2C, and to a lesser extent the polypeptide 3ABC, could be used to differentiate potential carrier convalescent animals from vaccinated livestock.