Purification and immunochemical study of Plasmodium falciparum exoantigens.

Plasmodium falciparum, in in vitro culture, elaborated many antigens including soluble exoantigens that are released into the culture medium. Anionic and cationic methods of isolating these antigens offer a great potential for large scale purification from medium that is rich in proteins but contains relatively low concentrations of P. falciparum specific antigens. These exoantigens have cationic and anionic dependent elution profiles (pI between 3.7 and 4.8). Five apparent molecular weight entities (58, 80, 145, 200, and 290 kdaltons) have been determined by GEDELISA. Susceptibility to lipase and to a proteolytic enzyme confirmed the proteinaceous nature of the antigens. They were isolated from 4 strains of different geographic origin, indicating their ubiquitous nature. The analogy of these exoantigens to circulating antigens in patients with acute malaria and their potential usefulness in immunodiagnosis and immunoprophylaxis are discussed.