Isotypes of naturally acquired antibodies to a repetitive & non-repetitive epitope on Plasmodium falciparum surface proteins in an endemic area of Sri Lanka.

Isotypes of antibodies in adults and 7-15 yr old children living in a malaria endemic area of Sri Lanka were measured by radioimmunoassay against synthetic target antigens derived from two Plasmodium falciparum surface proteins. Greater than 50 per cent of the sample population possessed IgM antibodies while < or = 13 per cent developed each of the IgG antibody isotypes against a repetitive epitope present on the circumsporozoite protein (CS repeat). A more even distribution of IgM, IgG1, IgG2, IgG3 and IgG4 antibodies was seen against a non-repetitive epitope (P103) on a 45 kDa merozoite surface protein. This difference is attributed to a T-independent antibody response against the CS repeat.