Characterization of the lipopolysaccharide of Yersinia pestis

Lipopolysaccharide (LPS) extracted from eight strains of Yersinia pestis, w hich had been cultured at 28 or 37 degreesC, reacted equally well, in Weste rn blots, with four monoclonal antibodies generated against the LPS from a single strain of Y. pestis cultured at 28 degreesC. LPS was extracted and p urified from Y. pestis strain GB, which had been cultured at 28 degreesC. W hen the LPS was analysed by SDS-PAGE and MALDI-TOF mass spectrometry it was found to be devoid of an O-antigen. The LPS possessed activity of 2.7 endo toxin units/ng in the Limulus amoebocyte lysate assay. The LPS stimulated t he production of TNF alpha and IL-6 from mouse macrophages, but was less ac tive in these assays than LPS isolated from Escherichia coli strain 0111. Y . pestis LPS, either alone or with cholera toxin B subunit, was used to imm unize mice. Either immunization schedule resulted in the development of an antibody response to LPS. However, this response did not provide protection against 100 MLD of Y. pestis strain GB.