Specific and non-specific mouse protection induced by different chemotypes of the Pseudomonas aeruginosa lipopolysaccharides

Abstract Lipopolysaccharides (LPS) of Pseudomonas aeruginosa were studied by the mouse active, cross-protection test. The primary structure of O-specific polysaccharides (O-repeating units) of different chemotypes was determined and their cross-protective activity demonstrated. Low doses of LPS (0.1–1 μg) stimulated chemotype-specific protection against P. aeruginosa in mice. This immunity was associated with the primary structure of the LPS and it lasted for 14 days after the first or second immunization. High doses of LPS (10–100 μg) induced cross-protection against P. aeruginosa in mice. The cross-protective capacity was caused evidently by the secondary structure or conformation of LPS molecule, i.e. by the common conformational protective determinant. This cross-protection lasted for only 5 days after the first or second immunization.