Tubulin and high-molecular-weight polypeptides as Giardia lamblia antigens.

We determined the antigenic specificities of nine murine monoclonal antibodies to Giardia lamblia. Four distinct antibody reaction patterns were detected by immunofluorescence with G. lamblia trophozoites. Four monoclonal antibodies which reacted with the body but not the flagella of the whole trophozoites recognized two polypeptides of 170,000 and 155,000 molecular weights by immunoblotting. Two antibodies reacting with both the flagella and body also reacted with 170,000- and 155,000-molecular-weight antigens. An antibody specific for the G. lamblia attachment disk and two specific for flagella by immunofluorescence were found to react with 53,000- and 55,000-molecular-weight polypeptides by immunoblotting. These antigens comigrated with purified bovine brain tubulin, and their respective antibodies reacted in immunoblots with purified bovine brain tubulin. The antigens identified in this report were found to be present in Giardia cytoskeletal preparations. All antigens were pronase labile and heat stable. Four strains of G. lamblia reacted similarly in immunofluorescence assays as well as in immunoblotting assays.