Interactions between Yersinia enterocolitica and the host with special reference to virulence plasmid encoded...

This thesis is based on 8 publications and a review of the literature. The aim was to summarize present knowledge on molecular components of Yersinia enterocolitica involved in (i) adhesion, with special reference to plasmid encoded factors and (ii) induction of antibodies in the host, and the quantitation of these two phenomena. Adhesion of Y. enterocolitica was quantitatively studied by methods that measured binding to cultured epithelial cells, mucosal constituents immobilized on polystyrene, intestinal tissue, and nonbiological solid surfaces. The chromosomal inv and ail gene products have been shown by others to be independently able to mediate adhesion to and invasion of cultured epithelial cells. However, the Yersinia virulence plasmid, pYV, also encodes for at least one product that may mediate adhesion. It was shown that pYV carrying Y. enterocolitica strains adhered more efficiently than their isogenic pYV cured derivatives to rabbit and human ileal intestinal tissue and to rabbit ileal brush border membrane vesicles (BBVs). Using Y. enterocolitica mutants that were defective for production of the pYV encoded outer membrane protein, YadA, and Escherichia coli strains carrying the cloned yadA gene it was verified that YadA was responsible for the pYV encoded adhesion. The YadA promoted adhesion was found likely to be non-specific and, at least in part, mediated by hydrophobic interaction. YadA, however, also mediated binding to one or more constituents present in intestinal mucus. Such binding led to decreased ability to penetrate a layer of mucus in vitro and subsequent decreased ability to adhere to BBVs. Based upon these results, it remains uncertain whether Y. enterocolitica is able to benefit from the YadA mediated adhesion in the intestinal millieu. In vivo results have suggested that expression of YadA confers on Y. enterocolitica an increased ability to colonize the intestine, but no definitive conclusions have been reached so far. A large number of antigens were identified in Y. enterocolitica by means of crossed immunoelectrophoresis (XIE). Quantitation of serological cross-reactions between chromosome-encoded Y. enterocolitica antigens and antigens from other bacterial species was performed by means of XIE and proved useful for taxonomic purposes. Using XIE it was shown that infection with Y. enterocolitica induced an antibody response against a wide range of antigens. Tube agglutination, enzyme linked immunosorbent assays (ELISAs) using purified lipopolysaccharide (LPS) or formalin-killed whole pYV carrying cells as antigens, and XIE were evaluated for their applicability to detect recent Y. enterocolitica O:3 infection.(ABSTRACT TRUNCATED AT 400 WORDS)