INFLUENCE OF ANTIBODIES IN MOTHERS MILK ON ANTIGENIC VARIATION OF GIARDIA-LAMBLIA IN THE MURINE MOTHER-OFFSPRING MODEL OF INFECTION

In the present study, neonatal ZU.ICR mice and their mothers were infe cted with trophozoites of Giardia lamblia clone GS/M-83-H7 expressing the variant surface protein (VSP) H7. The infection experiments includ ed a detailed analysis of the specificities of anti-Giardia immunoglob ulin A (IgA) antibodies in mother's milk and a determination of the ef fects of the milk antibodies on both the growth of the parasite during in vitro cultivation and colonization of the parasite within the inte stine of suckling offspring. These investigations revealed that transi ently emerging milk IgA antibodies against a variant-specific 314-amin o-acid N-terminal region of VSP H7 exhibit a strong parasiticidal effe ct on VSP H7-type trophozoites both in vitro and in vivo. These findin gs indicated that parasiticidal effects of local IgA antibodies agains t the N-terminal part of VSP H7 select for new variant types within th e intestinal parasite population of suckling mice. The selective influ ence of such antibodies promotes in vivo antigenic variation of G. lam blia clone GS/M-83-H7 and modulates the early course of parasite infec tion in these animals.