677 SPECIFIC IgA AND IgG INTERFERE WITH G. MURIS ADHERENCE TO INTESTINAL EPITHELIUM

Abstract

Mucosal adherence may contribute to the pathogenicity of Giardia. Factors implicated as mediators of adherence of this pathogen to the mucosal surface include lectins and antibodies. We have developed a method to examine adherence of G. muris trophozoites(TR) to intestinal epithelium to evaluate the role of anti-Giardia milk and serum antibodies. Uninfected CF1 mice were anesthetized, and a 2 cm segment of small intestine isolated. The ends were ligated and resulting sac injected with TR (5 × 105) and 200 μl of normal(NM) or immune(IM) mouse milk (13% V/V), hyperimmune(IRS) or normal rabbit serum(NRS)(40% V/V) and their IgG fractions. Following one hour of incubation, the animals were sacrified by intracardiac infusion of Ringer's lactate 30mM EDTA. The sac was removed, inverted and agitated with liberation of epithelial sheets. Adherence was assessed microscopically by counting the number of TR adherent to 10 villi isolated from each animal studied. NM decreased the number of adherent TR from 21.8 ± 3.5/10 villi in media alone to 13.4 ± 3.2(p<.01). IM further decreased the number of adherent TR to 6.6 ± 2.5 (p<.001). Addtion of NRS had no effect on adherence. IRS decreased the number of adherent parasites to 8.2 ± 2.1(p<.001). A decrease was also observed in the presence of the IgG fractions of IRS 13.2 ± 7.9, compared to the IgG fraction of NRS 23.7 ± 2.5 (p<.05). These findings suggest that specific anti-Giardia antibodies interfere with parasite adherence to the mucosal surface. This may represent an important mechanism, resulting in clearance of Giardia infection by antiparasite antibodies.