Immunogeneity and structural organisation of some pLCR-encoded proteins of Yersinia pestis.

A novel method of cultivation of Yersinia pestis EV-76 and its isogenic strains KM-217 (pPst-;pCad+;pFra-) and KM-218 (pPst-;pCad-;pFra-) and careful extraction of Y. pestis proteins (YPPs) permitted isolation of >35 low Ca2+ response plasmid (pLCR)-encoded products, some of which are potentially new members of the LCR family. Immunisation with each YPP demonstrated that 25-, 54-, 72- and 87-kDa YPPs provided the highest level of protection in mice challenged with Y. pestis virulent strain 231. Their immunological relationship was established with monoclonal antibodies (MAbs) and revealed several common properties, including oligosaccharide binding with specificity for N-acetylglucosamine. Affinity chromatography with MAb to the 25-kDa YPP permitted purification of the relevant antigen and its precursor. Their existence in the form of a complicated protein molecule was shown.