Comparison of properties between virulent and attenuated strains of transmissible gastroenteritis virus

Strains of transmissible gastroenteritis (TGE) virus possessing different pathogenicity were examined for stability to digestive enzymes and acid, and growth at various temperatures. In growth experiments, virus titer obtained at 37 degrees C were about equal between attenuated and virulent strains, but titers attained by the attenuated strain were higher at 30 degrees C. The attenuated virus multiplied at 28 degrees C, but the virulent virus did not at this temperature. The virulent virus was significantly stable to trypsin and pepsin, but the attenuated virus was inactivated rapidly by these proteolytic enzymes. No significant differences were observed in stability to acid between the attenuated and virulent strains. At different pH, both lost their infectivity more rapidly at 37 degrees C than at 22 degrees C.