Department of Immunology, Armed Forces Research Institute of Medical Sciences (AFRIMS), Department of Immunology, Walter Reed Army Institute of Research, Smith, Kline and Beckman Laboratories, King of Prussia, Bangkok, Thailand
Antibody responses to the glycoprotein precursor of the major merozoite surface antigens of Plasmodium falciparum (gp195) were investigated in acutely infected Thai adults. Specific IgG antibody was assayed by enzyme-linked immunosorbent assay using a recombinant fragment derived from the N-terminal region of gp195 as the capture antigen. Two control groups were found to be without significant cross-reacting antibody. Among occupationally exposed soldiers, 84 of 85 men developed positive antibody responses during acute falciparum malaria. Mean antibody levels began to increase at the time of diagnosis, peaking, often at high titers, within two weeks, and then decreased with an initial serum half-life of less than one month. The high frequency of gp195 antibody responses underscores a potential role in serodiagnosis, whereas the dynamic nature of the response suggests that a rigorous schedule of prospective serum sampling will be required to accurately assess the relationship between these antibodies and protection.