Protective antigens from El Tor vibrios. 2. Responses in animals and man to a partially purified Ogawa lipopolysaccharide antigen.

A previous report described the extraction and purification of a mouse-protective lipopolysaccharide antigen from culture supernatants of an El Tor vibrio of the Ogawa subtype. The chemical procedures for complete purification were complex, and considerable antigen was lost. The present paper describes a simpler method of obtaining an antigen of only slightly less purity in considerably improved yield. The method appears to be feasible for the preparation of an antigen that might be suitable for extensive immunization studies in humans.The antigen has been compared with the purified lipopolysaccharide and the Ogawa reference vaccine supplied by the National Institutes of Health with respect to active protection in mice, toxicity in mice and rabbits, and ability to produce passive mouse-protective antibody and vibriocidal antibody in rabbits. It has also been administered to a small number of volunteers in whom it was studied for its reaction-producing properties and its ability to produce agglutinin, vibriocidin and passive mouse-protective antibody. Little toxicity was found at dosages that induced very significant antibody production, and antibody remained elevated for at least six months.