Antibodies to Plasmodium falciparum Antigens Vary by Age and Antigen in Children in a Malaria-Holoendemic Area of Kenya

BACKGROUND:Antibodies are important in protection against infection and disease caused by Plasmodium falciparum, but the frequencies of antibodies to multiple P. falciparum antigens in children are not well-characterized. METHODS:IgG and IgM antibodies to the vaccine candidate antigens circumsporozoite protein, thrombospondin-related adhesive protein, liver stage antigen-1, apical membrane antigen-1, erythrocyte-binding antigen-175 and merozoite surface protein-1 were measured by enzyme-linked immunosorbent assay in 110 children 0–50 months of age in a malaria holoendemic area of Kenya. RESULTS:A similar pattern was seen for IgG antibodies to circumsporozoite protein, thrombospondin-related adhesive protein, apical membrane antigen-1 and erythrocyte-binding antigen-175high frequencies (70–90%) in children 0–4 months of age; a decrease in children 5–20 months of age (35–71%); and progressive increases in children 21–36 and 37–50 months of age (53–80% and 60–100%, respectively). In contrast, IgG antibodies to liver stage antigen-1 were infrequent in children 0–4 months of age (5%) and increased with age to 64%, and IgG antibody frequencies to merozoite surface protein-1 were similar across age groups (26–52%). IgG antibodies to all antigens were predominantly of the IgG1 and IgG3 subclasses. Frequencies of IgM antibodies to all antigens were low in children 0–4 months of age (0–15%) and increased with age (24–56% in the oldest children). CONCLUSION:In children in a malaria-holoendemic area, IgM antibody to all P. falciparum antigens is infrequent in the first 4 months of life but increases with age and increased exposure. The pattern of age-related IgG response frequencies to P. falciparum antigens varies significantly by antigen.