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Ribonuclease-sensitive ribosomal vaccine of Pseudomonas aeruginosa

In mice, active protection against Pseudomonas aeruginosa could be induced with two fractions derived from a crude preparation of ribosomes from P. aeruginosa. The two fractions were obtained by gel filtration chromatography of the crude ribosomal preparation on Sepharose CL-2B. In fraction I, less than 1% of the ribonucleic acid (RNA) applied to the column was recovered. Fraction II contained RNA and protein in a ratio of 1.94. The presence of ribosomes in this fraction was confirmed by analysis on a sucrose density gradient. The protection by fraction I was not affected by treatment with ribonuclease; in contrast, incubation of fraction II with ribonuclease completely abolished active protection. Fraction I contained lipopolysaccharide (LPS) as was indicated by the presence of 2-keto-3-deoxyoctonic acid. No LPS was found in fraction II. The adjuvant dimethyl dioctadecyl ammonium bromide enhanced the protection by fraction II; however, immunity by a low dose of fraction I was abolished by dimethyl dioctadecyl ammonium bromide. Protection by fractions I and II appeared to be restricted to the homologous serotype of P. aeruginosa. These results indicate that RNA is required for protection by fraction II. Active protection by fraction I is likely due to LPS.