Antimicrobial action of antibodies against Giardia muris trophozoites.

The activities of immune serum and trophozoite-specific MoAb were examined in vitro and in vivo. Immune serum and anti-Giardia muris MoAb caused immobilization of the trophozoites in vitro and were cytotoxic for trophozoites in the presence of exogenous complement. Both immune serum obtained from experimentally infected mice and anti-G. muris MoAb administered directly into the duodenum of mice significantly reduced the number of trophozoites in the small intestine during the acute phase of the infection. These results suggest that serum antibodies play a central role in the elimination of the primary Giardia infection.