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.