Identification of Target Antigens of Asexual Blood Stages of Plasmodium falciparum

Seven monoclonal antibodies (McAbs) specific for Plasmodium falciparum (Pf), humanimmune sera of three individuals, two adults and one child, living in a malaria endemic area inHainan Island of China and immune sera of BALB/c mice immunized with the erythrocytic stages ofPF were used to identify the target antigens of asexual blood stages of Pf. TheI-labeled surfaceantigens with apparent molecular weights of 125, 115, 83, 74 and 67 KDa were mainly recognizedby McAbs 93A3, 94B5, 92D4 and 93D4, but theI-labeled surface antigens of 200 and 19 KDawere recognized by McAb 94Dl alone. In addition, theS-methionine- labeled target antigens of183, 125, 83 and 55 KDa were also recognized by McAbs 93A3, 94B5 and 94C3. The McAb21E3 against the culture supernatant antigen of Pf only recognized the antigen of 125 KDa labeledwithS-methionine. The human immune sera from the adulst living in a malaria endemic area andmouse immune sera not only immunoprecipitated the target antigens which were recognized by theMcAbs but also immunoprecipitated the polypeptides of 140, 100 and some lower - molecularweight. But these target antigens recognized by McAbs, adult immune sera of and mouse immunesera could not be immunoprecipitated by human immune serum of the child with a primary infec-tion. With the antigen competition assay, the unlabeled antigens of Pf could strongly inhibit the im-mune reaction between the McAbs and theI-labeled antigens of Pf. It suggested that the antigensrecognized by McAbs and polyvalent immune sera were specific target antigens.