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-175: high 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.