DIFFERENTIAL CONTRIBUTION OF YERSINIA-ENTEROCOLITICA VIRULENCE FACTORS TO EVASION OF MICROBICIDAL ACTION OF NEUTROPHILS

The differential contribution of the virulence factors invasin, protei n tyrosine phosphatase (YopH), cytotoxin (YopE), and adhesin (YadA) of Yersinia enterocolitica to evasion of the antibacterial activities of polymorphonuclear leukocytes (PMNs) (oxidative burst, phagocytosis, k illing) was analyzed. We constructed virulence gene knockout mutants a nd a novel two-plasmid system allowing production and secretion of ind ividual virulence factors. Wild-type Y. enterocolitica WA-314 harborin g the virulence plasmid pYVO8 resisted phagocytosis and killing by PMN s. Moreover, strain WA-314 was able to inhibit the neutrophil oxidativ e burst upon stimulation with opsonized zymosan independently on prein cubation with normal human serum or YadA-specific serum. These phenoty pic properties of strain WA-314 were differentially affected when muta nts impaired in YadA production or Yop secretion were used. A more det ailed analysis revealed that YopH plays the dominant role in suppressi on of the antibacterial action of PMNs without damaging the cells. The YopH suppressing effect could be enhanced by coproduction of YopE and YadA. The contribution of YadA is attributed to the adhesin function promoting interaction with PMNs under both opsonizing and nonopsonizin g conditions. In contrast, invasin seems to mediate only opsonin-indep endent interaction with PMNs. Taken together, our results demonstrate that YopH, YopE, and YadA act in concert towards neutrophil attack to enable extracellular survival of Y. enterocolitica in host tissue.