HELICOBACTER-PYLORI UREASE SIGNIFICANTLY REDUCES OPSONIZATION BY HUMAN-COMPLEMENT

The role of Helicobacter pylori urease in opsonization by human comple ment was investigated H. pylori wild type strain N6 and isogenic mutan ts lacking either the large urease subunit (UreB) or an accessory urea se protein (UreG) were incubated with different sera. C3b bound to the bacteria was measured by specific staining and flow cytometry. As com pared with opsonization of N6 and the UreG-lacking mutant, opsonizatio n of the UreB-lacking mutant was significantly increased after incubat ion with sera from both H. pylori uninfected (P < .001) or infected (P < .05) persons. However, when sera from uninfected persons were used, effective opsonization of this mutant proved to be dependent mainly o n the classical pathway of complement activation. Irrespective of the serum used, opsonization values were very low after selective inactiva tion of the classical or the alternative pathway. Reduced opsonization of the urease-expressing strains could, to some extent, result from d egradation of bound C3b.