TRANSMISSION-BLOCKING EFFECTS OF SERA FROM MALARIA-EXPOSED INDIVIDUALS ON PLASMODIUM-FALCIPARUM ISOLATES FROM GAMETOCYTE CARRIERS

Sera from donors exposed to malaria were tested for their ability to b lock the transmission of isolates from Cameroonian Plasmodium falcipar um gametocyte carriers. Sera were selected from amongst Cameroonian an d Gambian donors who had positive antibody reactivity against the surf ace of activated gametes and against epitopes of Pfs 48/45 (a potentia l transmission-blocking vaccine candidate antigen). Aliquots of washed blood from gametocyte carriers were resuspended in test and control s era and fed to An, gambiae mosquitoes via a membrane feeder. Compariso ns of the prevalence and intensity of infections in dissected mosquito es showed variations in the ability of sera to block the transmission of the different isolates. Sera were identified that had little or no blocking effect on the transmission of isolates unless the isolate was poorly infectious. Some sera completely blocked the transmission of s ome isolates whilst having little or no effect on others. The observed variation in transmission-modulating activity may have implications f or the development of a transmission-blocking vaccine.