Fractionation, characterization and diagnostic potential of filarial antigens isolated from hydrocoele fluid in bancroftian filariasis.

Filarial antigen was isolated from hydrocoele fluid and fractionated on Ultrogel AcA 44. Six protein fractions (HFA C1 to HFA C6) were chromatographically separated from the column. Of the 4 antigenic fractions (HFA C1, HFA C2, HFA C3 and HFA C5), HFA C3 was a major reactive fraction with filarial serum immunoglobulin G. Analysis of HFA C3 by sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE) yielded 18 bands of Mr 18,000-160,000. Two fractions, HFA C3-7 and HFA C3-9 of Mr 48,000-55,000 and 32,000-39,000 obtained by gel elution, were antigenic in an enzyme-linked immunosorbent assay (ELISA). SDS-PAGE immunoblotting confirmed the ELISA by identifying 3 immunoreactive bands of Mr 51,000, 38,000 and 35,000. The diagnostic potential of HFA C3-7 and HFA C3-9 was compared in serodiagnosis of active infections and diseased states. HFA C3-9 showed greater sensitivity in detection of filarial specific IgM antibody in cases with microfilaraemia. Physicochemical characterization indicated the protein nature of HFA C3-9.