Immunoblotting of Yersinia plasmid-encoded released proteins: a tool for serodiagnosis

The plasmid-encoded, released proteins (RPs) of Yersinia enterocolitica serotypes 09 and 03 were separated by sodium dodecyl sulfate (SDS)-pore gradient gel electrophoresis. The RP-patterns of both serotypes proved to be identical. Five major proteins of M(r) 27,000, 34,700, 35,600, 45,800, and 46,800 were detected. Spontaneously plasmid-cured derivatives of the two serotypes lost the feature of protein release. By immunoblotting of RP with sera from patients suffering from acute Yersinia infections, specific and reproducible band patterns were obtained. Laser scan densitometry was applied to record the immunoreactions quantitatively. Predominant bands were detected at an M(r) of 34,700 and 35,600. IgA and IgM antibodies appeared as acute-phase markers rapidly decreasing in the reconvalescent phase. In contrast, immunoblots of patients with supposed chronic yersiniosis were characterized by a persisting IgA and elevated IgG reactivity. The application of RP as diagnostic antigens proved to be advantageous because they are naturally separated from cross-reacting proteins, common to pathogenic and nonpathogenic strains of Yersinia enterocolitica and Y. pseudotuberculosis.