Characterization of antigens from erythrocytic stages of Plasmodium falciparum and Plasmodium cynomolgi reacting with sera of Malaysian Orang Asli living in malaria endemic areas

Abstract

A study was performed to identify the antigenic polypeptides present in both the schizonts and trophozoites of Plasmodium falciparum and Plasmodium cynomolgi that reacted with sera from Orang Asli living in malaria endemic areas in Peninsular Malaysia. Immunoprecipitation with ³⁵S-methionine labelled parasite antigens revealed strong reactivity of the sera with four dominant polypeptides of molecular weight 120, 90, 88 and 82 kilodaltons (kd) present in P falciparum schizonts and trophozoites. Some of the sera reacted with several other minor polypeptides of molecular weight 105, 60, 55, 45, 35, 28, 17 and 15 kd. In immunoblot with P. cynomolgi schizont antigens, these sera reacted strongly with polypeptides of molecular weight 120, I05, 96, 86 and 70 kd. Some of these sera also reacted with a 66 kd polypeptide. lmmunoblots of these sera with P cynomolgi trophozoite antigens revealed a less intense reaction. However, a number of polypeptides were reactive with these sera and they included those of molecular weight 120, 90, 86, 70, 60, 26 and 24 kd. The dominant polypeptides of the two Plasmodium species identified in this study should be further studied to determine their role in the induction of host's protective response and their usefulness in the development of diagnostic tests for malaria.