Isolation and Characterization of a Protective Antigen-Containing Particle from Culture Supernatant Fluids of Erysipelothrix rhusiopathiae.

The mouse-protective activity of Erysipelothrix rhusiopathiae culture supernatant fluids exists in a polydisperse form, ranging in density from aggregates which sediment at 10,000 x g for 3 hr to soluble units which will not sediment at 198,000 x g for 12 hr. A partially purified protective antigen has been isolated from the aggregates sedimented from a concentrate of the culture supernatant fluid at 20,000 x g for 3 hr. These aggregates contained the major protective antigen or antigens of E. rhusiopathiae, since, in addition to inducing active immunity, they adsorbed essentially all of the passively protecting antibody from rabbit antiserum produced by immunization with whole culture. The protective activity in these aggregates was destroyed by trypsin and greatly diminished by muramidase and heating at 64 C, but was not affected by lipase or ribonuclease.