Immune response in swine given soluble antigens from group E Streptococcus.

Swine were given a series of injections of soluble or whole cell antigens of group E Streptococcus (GES). In experiment 1, swine given autoclaved extracts developed greater amounts of antibody to antiphagocytic factor (as detected with bactericidal and long-chain tests) than did swine given pepsin-extracted or whole cell antigens, and the swine given extract developed fewer abscesses when challenge exposed with live virulent GES added to their feed. In experiment 2, swine given injections of concentrated autoclaved extract develped higher antiphagocytic factor antibody titers than did control swine given injections of physiologic saline solution. When challenge exposed with live virulent GES by exposure to carrier swine, swine that were given extract developed 71.4% fewer abscesses than did the control swine. Furthermore, 58.3% of the abscesses in the swine that were given extrac" were less than 1 cm in diameter as compared with 38.2% of the abscesses in the controls, suggesting that the development of some abscesses was arrested in vaccinated swine. Data indicate that a degree of immunity to streptococcal lymphadenitis of swine can be induced by vaccinating swine with nonliving GES antigen.