Identification of a 17000 molecular weight antigenic polypeptide in transmissible gastroenteritis virus-infected...

Pulse labelling of cells with [35S]methionine at different times after infection followed by SDS-PAGE was used to resolve and to identify polypeptides designated as specific to transmissible gastroenteritis virus (TGEV)-infected swine testicular (ST) cell cultures. The major TGEV structural proteins, with apparent molecular weights of 200,000 (200K), 47K and 30K were detected in radiolabelled cell extracts by 6 h postinfection. Additionally, a 17K major polypeptide was present in infected cells but not in mock-infected control cultures. Labelling with [3H]glucosamine revealed only the 200K and 30K proteins to be glycosylated. TGEV-primed porcine lymphocytes, secondarily stimulated in vitro with sucrose gradient-purified virus, produced antibody only to the two glycoproteins (gp) indicating that the 17K polypeptide is not a surface feature of the virion. Two pigs were infected oronasally with the virulent Miller strain of TGEV and their sera were analysed by immunoprecipitation. At 25 days postinfection convalescent sera responded strongly to gp30 and gp200 and there was a weak initial response to the 17K polypeptide. Serum immunoglobulins at 60 days postinfection reacted strongly to the 17K protein while the antibody response to gp30 was significantly reduced and that to gp200 was slightly reduced.