Protective antigens from El Tor vibrios. 1. The preparation and properties of a purified protective antigen from an El Tor vibrio (Ogawa subtype)

A biochemically and immunologically homogeneous antigenic fraction having the properties of a lipopolysaccharide has been isolated from the culture supernatant of an El Tor vibrio (Ogawa subtype). This antigen was very specifically protective for mice challenged with Ogawa strains of either El Tor vibrios or Vibrio cholerae. Rabbit antisera prepared against the antigen were passively protective for mice and highly vibriocidal but had little agglutinating activity. However, the antigen was able specifically to absorb agglutinins, as well as mouse-protective and vibriocidal antibody from serum prepared against whole bacterial cells. The specific protective activity of this lipopolysaccharide was much greater than that of vaccines made from whole bacterial cells, and its toxicity in animals was about equivalent to that of whole cells. The relationship of activity to toxicity therefore represented an improvement over the vaccines that were studied.

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.