[The autoagglutination factor of plague pathogen--cross-reacting antigen]

An antigen similar to the autoagglutination factor (AF) of plague pathogen in immunochemical specificity was sought in 22 bacterial species. For this, an immunoglobulin anti-AF diagnosticum that is the sheep erythrocytes sensitized with rabbit immune serum to the AF preparation isolated from the plasmid-free variant of the Yersinia pestis strain EV76. The bacteriological study applying a passive hemagglutination assay revealed AF-like antigens not only in all study strains (n = 30) of Y. pestis, but also in Yersinia pseudotuberculosis, Klebsiella pneumoniae, Pseudomonas aeruginosa, and Proteus vulgaris. These bacteria were used to prepare AF = like antigen preparations that reacted with rabbit anti-AF serum in dot blot immunoassay. Also, as Y. pestis, AF-like antigens in polyacrylamide gel were detected as multiple protein bands that differed in mobility in Yersiniae and heterologous bacteria. Differences were found in the properties of AF-line antigens of 5 species of bacteria (sensitivity to temperature and formalin, binding to the cell surface, which enabled differentiation of serological reactions caused by AP-like antigens of other bacteria. Thus, Y. pestis AF is a cross-reacting antigen that, despite its immunochemical similarity with AF-like antigens of other bacteria, was ascertained to differ from them in properties. The findings are of interest for searching for new diagnostic tests to detect the Cafl- strains of the plague pathogen and for differentiating the causative organisms of plague and pseudotuberculosis.