[Protective protein antigens of Pseudomonas aeruginosa].

Partially purified water extract was obtained from the initial water extract by ultracentrifugation. Nine protein fractions differing in molecular weight, homogeneity and the content of lipopolysaccharide (LPS) were obtained by stepwise precipitation with ammonium sulfate and subsequent fractionation in columns packed with Sephadex G-100 and DEAE cellulose. Two protein fractions with a molecular weight of 30000 and 40000 daltons were practically free of LPS. These fractions were homogeneous as shown by analytical centrifugation and formed a single precipitation line with P. aeruginosa antiserum; both fractions were found to be antigenically identical. In the enzyme immunoassay these two fractions proved to be least active in comparison with the other protein fractions, but when used for the immunization of rabbits, they induced the formation of specific protective (for mice) antibodies. Both antisera were equally active in the experiments of the passive protection of mice. The isolated LPS-free proteins are supposed to be the proteins of the outer membrane of P. aeruginosa cell wall and have the properties of protective antigens.