Giardia lamblia: RNA translation products.

The in vitro translation products of two different human isolates of Giardia lamblia, WB 2x and GS/E, were compared in order to determine common protein constituents and to identify proteins recognized by the infected host. Multiple polypeptides ranging from 20 to 185 kDa were synthesized using a rabbit reticulocyte cell-free translation system and although most were identical some differences were noted. GS/E compared to WB 2x showed different polypeptides of 23.5, 24.5, 26.5, 27.5, 32.5, 33.5, and 41 kDa. Some of these polypeptides were antigenic and were immunoprecipitated with anti-isolate antiserum from experimentally infected humans and gerbils. The sera of humans experimentally infected with isolate GS/M recognized a 24-kDa polypeptide from WB 2x and 23.5- and 24.5-kDa polypeptides from GS/E in vitro translation products. Sera from WB 2x- and GS/E-infected gerbils recognized 74- and 24-kDa polypeptides present in WB 2x translation products and 23.5-, 24.5-, 32.5-, 33.5-, and 74-kDa polypeptides when GS/E in vitro translation products were used. These studies identified both unique and common antigens in two different Giardia isolates and they may be of use in the serologic diagnosis of giardiasis and characterization of Giardia isolates.