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Giardia-specific antibodies: their in-vitro anti-parasitic effects and a preliminary characterization of their target antigens Ryan, Paula Patricia


In order to evaluate host defense mechanisms against the intestinal parasite G.lamblia, assays have been established which measure the ability of both immune sera and fecal extracts to immobilize Giardia trophozoites. The immobilizing activity of immune serum against two strains of Giardia was shown to be dependent on complement. When immune serum was absorbed against live trophozoites, the immobilizing activity was abolished. These data, in conjunction with results from immunoblots and immunofluorescense assays, indicate that a complement dependent, anti-giardia antibody response renders trophozoites immobilized in-vitro. In an attempt to use these anti-parasitic antibodies to identify giardia surface antigens, an immunoabsorption technique was developed to isolate immobilizing antibodies from immune sera by absorbing them to the surface of trophozoites. Surface-bound antibodies were recovered using a low pH glycine buffer. Antibodies which were eluted from the surface of trophozoites could not be shown to possess immobilizing activity. However, the surface-specific antibodies which were isolated were used to identify a number of Giardia surface antigens from preparations of whole trophozoite antigens as well as enriched membrane preparations.

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