Isolation and Partial Characterization of an Immunogenic Moiety Obtained from Salmonella typhimurium

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Ribosomal preparations obtained from Salmonella typhimurium by differential centrifugation and sodium dodecyl sulfate (SDS) treatment of the bacillary lysate were found to be immunogenic in F1 hybrid (C3H/HeJ × DBA/2J) and albino Swiss mice, as determined by progressive host survival. The immunity obtained was independent of the need for adjuvant and dependent on the dosage of immunogen given. Immunizations with the ribosomal preparations induced an immune response comparable to that obtained by vaccination with living organisms and significantly greater than that obtained by immunization with heat-killed salmonellae, purified lipopolysaccharide, or crude and SDS-treated endotoxin preparations. No effect on the immunogenicity of the ribosomal fraction was observed by enzymatic treatment with trypsin, Pronase, deoxyribonuclease, and pancreatic ribonuclease. Linear sucrose density gradient resolution of the preparations showed that the immunogenicity of the ribosomal fraction was not unique to any one of its subcomponents. Ethyl alcohol-precipitated, crude ribonucleic acid preparations obtained from the ribosomal and sucrose density-resolved ribosomal preparations were found to induce an immune response comparable to that obtained by immunization with the entire ribosomal fraction. Dialysis in doubly distilled demineralized water slightly reduced the immunogenicity of the preparation; however, comparable dialysis in 10−4M MgCl2-phosphate buffer did not. Chemical assays of the preparations found to be immunogenic were performed.