Surface-exposed antigenic determinants in outer membranes of wild Yersinia pestis isolates

Immunogenic surface exposed envelope proteins of Yersinia pestis strains were investigated with SDS-PAGE and immunoblots with antisera of immunized guinea pigs and convalescent patients. The sarkosyl-insoluble outer membrane proteins (OMPs) of three human isolates and one laboratory strain of Y. pestis grown in different rich media to exponential or stationary phase, and cultivated at 28 degrees C or 37 degrees C, were assayed for the presence of immunogenic peptides. Seven guinea-pig sera immunized with one of the four Y. pestis strains and four human sera from plague-infected patients indicated that at least four outer membrane proteins with molecular weights of 45 KDal, 42 KDal, 21 KDal and 16.5 KDal were strongly recognized by at least one of them. All but one of the guinea-pig serum and one human serum recognized the 45 KDal protein. The 42 KDal was identified only in outer membrane isolated from Y. pestis cells grown at 28 degrees C. All immunogenic OMPs were found in the four strains investigated. Labelling of intact Y. pestis cells with Iodogen and 131I further demonstrated the surface-exposed location of the immunogenic OMPs.