A new tool for the serodiagnosis of acute Plasmodium falciparum malaria in individuals with primary infection

We have developed an ELISA which detects, with high specificity, antibodies against a major surface protein of P. falciparum merozoites which is a processing product of the precursor glycoprotein gp190. This assay can be used in the diagnosis of acute malaria in individuals with primary infection. Two partial sequences of gp190 were expressed in E. coli as β-galactosidase (β-Gal) fusion proteins. The same sequences fused to chloramphenicol acetyltransferase (CAT) or mouse dihydrofolate reductase (DHFR) react with high frequency when sera of acute malaria patients are analyzed in immunoblots. Antibodies from such sera crosslink, via their antigen binding sites, the β-Gal fusions to the corresponding CAT or DHFR fusions adsorbed to a solid phase as demonstrated by the captured β-Gal activity. The assay is highly specific, shows extremely low cut off values and should therefore be widely applicable.