Résumé
Sodium dodecyl sulphate-polyacrylamide gel electrophoresis of circulating filarial antigen fraction-2 isolated from plasma of microfilaraemic patients with Wuchereria bancrofti infection has shown 21 bands with molecular weights ranging from 12 to 120 kDa. The gel (12 cm) was sliced at an interval of one cm and the eluates of all the gel slices viz., CFA2–1 to CFA2–12 showed the presence of filarial antigen by sandwich enzyme-linked immunosorbent assay. The low molecular weight circulating filarial antigen fractions were found to share a common epitope with Wuchereria bancrofti microfilariae excretory-secretory antigen and urinary filarial antigen. The 3 antigen fractions CFA2-1, CFA2–9 and CFA2–12 showed higher sensitivity in detecting filarial immunoglobulin Μ antibodies than immunoglobulin G antibodies. However CFA2–9 fraction was found useful in serological differentiation of microfilaraemics from those with disease manifestations when filarial immunoglobulin G antibodies were detected. The antigenic epitope of CFA2–1 appears to be a carbohydrate, whereas CFA2–9 appears to be protein in nature.
Résumé
Detection of filarial antigen in different groups of sera was carried out by sandwich as well as inhibition enzyme-linked immunosorbent assays using antibody-coated sticks. Both systems were found to be equally sensitive in detecting antigen in 90% of microfilariae carriers. Incorporation of avidin-biotin in the sandwich assay system increased the sensitivity of antigen detection from 10–6 to 10–16 pg. A 67% decrease in the number of false negative results was observed when the sensitive avidin-biotin inhibition enzymelinked immunosorbent assay system was used for analysis of filaria blood samples.