The merozoite surface protein 1 (MSP1) is the most abundant protein on the surface of the invasive merozoite stages of Plasmodium falciparum and has long been considered a key target of protective immunity. We used samples from a single controlled human malaria challenge study to test whether the full-length version of MSP1 (MSP1(FL)) induced antibodies that mediated Fc-IgG functional activity in five independent assays. We found that anti-MSP1(FL) antibodies induced complement fixation via …