Analysis of immunity to infection with Salmonella typhimurium in outbred mice. II. Isolation and immunogenicity of the protective non-O antigenic component from ribosomal vaccine.

The active component in crude ribosomal fraction (CRF) of Salmonella typhimurium, capable of inducing protective antibody, was partially purified by two series of chromatography (Sephadex G-150 and DEAE-Sepharose CL6B) after sodium dodecyl sulphate (SDS)-treated CRF was precipitated with ammonium sulphate. The major active component was eluted by 0.4-0.45 M NaCl from DEAE-Sepharose CL6B, and its molecular weight was 43,000 as determined by SDS-polyacrylamide gel electrophoresis. Immunization with the fraction containing 43,000 component alone did not always confer protection on CF1 mice, but its administration together with either the purified transfer RNA (tRNA) or Freund's complete adjuvant (FCA) was much more effective against infection with S. typhimurium. Antibody to the fraction containing 43,000 component was not only free in serum but also associated with peritoneal cells. Macrophages that had been exposed to the antibody had enhanced anti-bacterial activity. Western blot analysis showed that 43,000 component did not react to antiserum to lipopolysaccharide (LPS), but to antiserum to CRF. The antibody elicited by non-O antigenic component and the cell-mediated resistance stimulated by the adjuvant effect of RNA together confer effective protection on CF1 mice.