Studies on immunodiagnosis of dracunculiasis. I. Detection of specific serum antibodies

To explore the possibility for development of an immunodiagnostic test for Dracunculus medinensis infections, the antibody responses (IgG1, IgG2, IgG3, IgG4 and IgE) to antigen preparations made from adult female worms (ADGW) and first stage larvae (LVGW) of D. medinensis were analysed. By sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE)/Western blotting, sera from individuals with patent D. medinensis infection reacted extensively and similarly with ADGW and LVGW over a broad molecular weight range (5-200 kDa). Sera from individuals infected with Onchocerca volvulus (the major cross-reacting infection) had a more pronounced reaction with ADGW than LVGW, and only with antigens of molecular weights above 23 kDa. These findings were used to design an enzyme-linked immunosorbent assay (ELISA) with high sensitivity and specificity for D. medinensis infection. The most promising results were obtained when detecting for specific IgG4. Thus, when using LVGW, the assay had a sensitivity of 83% and a specificity of 97%. Refining the antigen into a low molecular weight filtrate improved the sensitivity to 92%, and the sensitivity was further improved (to 96%) when combining the results from two or more antibody types measured simultaneously, without affecting the specificity. The results were encouraging for the prospects for developing an applicable immunodiagnostic test for patent D. medinensis infections based on detection of specific serum antibodies.