A SOLUBLE PRECIPITATING ANTIGEN (HCA) FROM HOG CHOLERA VIRUS PROPAGATED IN TISSUE CULTURE. II. INCIDENCE OF HCA-ANTIBODIES IN SERA OF HOG CHOLERA-IMMUNE AND NONIMMUNE SWINE.

Some conditions are presented under which swine develop antibodies for a soluble hog cholera viral antigen (HCA). Precipitating antibodies for HCA were present in all of the immune and hyperimmune anti-hog cholera sera tested. Antibodies for HCA could not be detected in the sera from a large number of swine after vaccination with inactivated hog cholera virus. Many of these same swine did produce HCA-antibodies following challenge with virulent virus. The incidence of these antibodies was significantly higher 3 weeks to one month after challenge than at 10 days. About one-fourth of a smaller group of swine developed HCA-antibodies after vaccination with modified active hog cholera virus vaccine. Exposure to active hog cholera virus appears prerequisite for swine to develop HCA-antibodies.