[Electrophoretic and immunological analysis of native proteins secreted in vitro under conditions inducing Ysa (Yersinia secretion apparatus) by clinical isolates of Yersinia enterocolitica 1B/O8 in Poland].

Introduction: The high pathogenicity Yersinia enterocolitica 1B/O8 produce variety of virulence factors including chromosomal T3SS known as Ysa-Ysp system that is considered to act at the early stage of infection. The aim of the study was to examine the ability to produce Ysa-Ysp proteins in vitro by human clinical isolates of the epidemic Y. enterocolitica 1B/O8 strains in native conditions and immunological characterization of expressed proteins.

Methods: Seven Y. enterocolitica 1B/O8 isolates with known epidemiological link and the reference high pathogenicity strain WA-314 and six strains from the Institute Pasteur (France) were examined for production of Ysa-Ysp proteins according with procedure described by Matsumoto and Young (Mol. Microbiol., 2006, 59:689-76). All the isolates and strains were characterized by SDS-PAGE to determined Ysa-Ysp proteins profile. The immunological characterization was performed by using western-immunobloting method using sera from two immunized rabbits and from two patients with bacteriology confirmed Y. enterocolitica 1B/O8 infection.

Results: The reference strain WA-314 yielded typical Ysa-Ysp proteins profile. In contrast all the tested Y. enterocolitica 1B/O8 human isolates yielded the same SDS--PAGE profile that was apparently distinct from profile of Ysa-Ysp proteins of reference strain WA-314.

Conclusions: The Y. enterocolitica 1B/O8 isolates of the epidemic strain circulating in Poland were found to be unable to produce Ysa-Ysp proteins in vitro under conditions sufficient to stimulate expression of the Ysa-Ysp proteins in the reference strain WA-314 and strains from the Institute Pasteur (France). Our results may suggest that the ability to produce Ysa--Ysp proteins in concentrations sufficient to induce production of specific antibodies is not indispensible for Y. enterocolitica 1B/O8 infection in humans. The western-immunoblotting analysis of human serum samples showed that the antibodies were not induced by Ysa and Ysp proteins during infection caused by the epidemic strain of Y. enterocolitica 1B/O8 circulating in Poland. Similar, negative result was found with serum of a rabbit immunized intravenously by the reference strain WA-314. The project was funded by the National Science Centre in Cracov, Poland, grant N N401 076039.