Contribution of the mannan O side-chains to the adjuvant action of lipopolysaccharides.

Abstract

Klebsiella 03 lipopolysaccharide (LPS) and Escherichia coli 09 LPS were previously shown to have potent adjuvant activities in augmenting antibody response and delayed-type hypersensitivity to protein antigens. The R form LPS extracted from the O-specific polysaccharide-less mutants derived from Klebsiella 03 and E. coli 09 strains were characterized by chemical and electrophoretic analyses. The adjuvant activities of the R-LPS in augmenting antibody response and DTH to protein antigens were much weaker than those of the parental LPS. The strength of the adjuvant activities of the R-LPS was similar to that of the activities of Salmonella minnesota LPS and Ra-LPS. By contrast, polyclonal B-cell activation effects of the R-LPS were stronger than those of the parental LPS. The common feature of the parental LPS is that their O-specific polysaccharides are mannose homopolymers (mannans). From these results, it is suggested that mannose homopolymers as the O side-chains of LPS contribute to the action of LPS in enhancing strongly the T-cell dependent immune responses to protein antigens.