Antibodies against merozoite surface protein (MSP)-1(19) are a major component of the invasion-inhibitory response in individuals immune to malaria

Antibodies that bind to antigens expressed on the merozoite form of the mal aria parasite can inhibit parasite growth by preventing merozoite invasion of red blood cells. Inhibitory antibodies are found in the sera of malaria- immune individuals, however, the specificity of those that are important to this process is not known. In this paper, we have used allelic replacement to construct a Plasmodium falciparum parasite line that expresses the comp lete COOH-terminal fragment of merozoite surface protein (MSP)-1(19) from t he divergent rodent malaria P. chabaudi. By comparing this transfected line with parental parasites that differ only in MSP-1(19), we show that antibo dies specific for this domain are a major component of the inhibitory respo nse in P. falciparum-immune humans and P. chabaudi-immune mice. In some ind ividual human sera, MSP-1(19) antibodies dominated the inhibitory activity. The finding that antibodies to a small region of a single protein play a m ajor role in this process has important implications for malaria immunity a nd is strongly supportive of further understanding and development of MSP-1 (19)-based vaccines.