INHIBITION OF THE FC RECEPTOR-MEDIATED OXIDATIVE BURST IN MACROPHAGESBY THE YERSINIA-PSEUDOTUBERCULOSIS TYROSINE PHOSPHATASE

Suppression of host-cell-mediated immunity is a hallmark feature of Ye rsinia pseudotuberculosis infection. To better understand this process , the interaction of Y. pseudotuberculosis with macrophages and the ef fect of the virulence plasmid-encoded Yersinia tyrosine phosphatase (Y opH) on the oxidative burst was analyzed in a chemiluminescence assay. An oxidative burst was generated upon infection of macrophages with a plasmid-cured strain of Y. pseudotuberculosis opsonized with immunogl obulin G antibody. Infection with plasmid-containing Y. pseudatubercul osis inhibited the oxidative burst triggered by secondary infection wi th opsonized bacteria. The tyrosine phosphatase activity of YopH was n ecessary for this inhibition. These results indicate that YopH inhibit s Fe receptor-mediated signal transduction in macrophages in a global fashion. In addition, bacterial protein synthesis aas not required far macrophage inhibition, suggesting that YopH export and translocation are controlled at the posttranslational level.