DETECTION OF ANTIBODIES TO A 70KDA PLASMODIUM-FALCIPARUM EXOANTIGEN IN MALARIOUS SUBJECTS USING SYNTHETIC PEPTIDES

Indirect fluorescent antibody (IFA) tests and enzyme-linked immunosorb ent assays (ELISA) were used to measure antibodies to Plasmodium falci parum in patients with acute malaria from Bolivar State, Venezuela. An tibody titers increased significantly with repeated malarial episodes. IgG antibody responses to 4 synthetic peptides (termed C2, C3, C5, C1 0) derived from a 70 kDa P. falciparum (Indochina I/CDC strain) exoant igen were evaluated by a peptide-ELISA with overall positivity rates o f 20 %, 40 %, 20 % and 58 %, respectively. Seropositivity to peptide C 10 was consistently over 50 % (range 53-75 %) among patients of differ ent ages. Overall IgM reactivity to the respective peptides was 53 %, 30 %, 83 % and 70 %. IgM reactivity was generally greater in patients with primary malarial infections. The ELISA is a useful adjunct to the IFA in measuring naturally-occurring antibodies to specific parasite proteins.