Specific and nonspecific immunodiagnostic properties of recombinant and synthetic Plasmodium falciparum antigens.

Six Plasmodium falciparum/beta-galactosidase fusion proteins produced by a genomic DNA expression library, and two synthetic Plasmodium falciparum antigens were applied to ELISA and tested for their immunodiagnostic properties. Results were compared to reference methods, i.e. fluorescence antibody test with whole cell antigen and ELISA with detergent-soluble crude schizont antigen. Anti-Plasmodium falciparum antibodies could be detected by these molecular antigens to varying extents in human sera. Undesired reactivity to fusion proteins due to the high prevalence of antibodies to beta-galactosidase in human sera and undesired reactivity to one of the synthetic antigens (P12) frequently occurred. The antibodies responsible for the nonspecific reactivity could not be identified. It was concluded that the application of molecular Plasmodium falciparum antigens to ELISA represents a practicable approach to immunodiagnosis of malaria if the construction of epitopes that bind antibodies other than Plasmodium falciparum antibodies can be avoided.