Antibodies to Plasmodium falciparum gamete surface antigens in Papua New Guinea sera.

Sera from individuals living in malaria endemic areas of Papua New Guinea were tested for their effect on infectivity of Plasmodium falciparum gametocytes grown in culture to Anopheles freeborni mosquitoes. Consistent reduction of infectivity to less than 5% of control was observed with nine out of the 41 sera from the endemic area tested and also with three out of seven sera tested from individuals rarely exposed to malaria infection. Gamete surface antigens recognized by the sera were investigated by immunoprecipitation from 125I surface-labelled gametes extracted in SDS and Triton X-100. The main antigens recognized were of the same mol. wt (230, 48 and 45 kD) as those known to be targets of transmission-blocking monoclonal antibodies. A significant negative correlation was observed between the total ct/min immunoprecipitated from surface-labelled gametes by the sera and the average number of oocysts per gut observed in membrane feeding experiments with these sera. Spearmann's rank correlation coefficient indicated that suppression of infectivity correlated strongly with the presence of antibodies against the 230 kD protein; there was no significant correlation between suppression and antibodies to the 48/45 kD proteins. The antibody response to the different gamete surface antigens varied greatly in sera from the endemic areas suggesting that individuals respond differently to each gamete antigen.