Serological responses of Gambian children to immunization with the malariavaccine SPf66

Antibody responses to the malaria vaccine SPf66 and to its constituent pept ides were measured over a period of 2 years in Gambian children who had bee n immunized with SPf66 or with a control vaccine (inactivated polio vaccine ). Three hundred and six of 308 children (99%) who had received three doses of SPf66 vaccine had antibodies to SPf66 at a level above that found in Eu ropean controls who had not been exposed to malaria. Responses to the const ituent peptides derived from 35.1, 55.1 and 83.1-kDa proteins were found in 88%, 97% and 97% of children, respectively, 26% had an antibody response t o the NANP repeat peptide of circumsporozoite protein which is also include d in the SPf66 vaccine. A response to SPf66 was found in 22% of children wh o had received the control vaccine. Antibody responses to NANP, 35.1, 55.1 and 83.1-kDa peptide were found in 3%, 33%, 49% and 33% of these children. Overall, no significant correlation was found between the level of anti-SPf 66 antibody as the beginning of the malaria transmission season following v accination and the subsequent risk of malaria. However; further analysis sh owed that among the control children who had acquired antibodies to SPf66 a s a result of natural exposure to malaria, those with high levels of anti-S Pf66 were less at risk of malaria, perhaps reflecting their greater previou s exposure and thus immunity. In contrast, among children who had received three doses of SPf66, those with high antibody levels were at greater risk of have malaria during the subsequent malaria transmission season.