Diagnostic use of filarial antibody and antigen isolated from hydrocele fluid for human filariasis.

Paired samples of serum and hydrocele fluid of filarial patients associated with hydrocele were analysed for filarial antibody and antigen. Sera samples showed higher titers of filarial antibody and antigen compared to their corresponding hydrocele fluid samples. HFIgG isolated from hydrocele fluid was equally useful as FSIgG isolated from serum and detected filarial antigen in 23 out of 26 microfilaraemic sera, 7 out of 10 chronic sera and 3 out of 18 endemic normal sera by inhibition ELISA. Filarial antigen was isolated from hydrocele fluid. In inhibition ELISA antigen fraction, HFA-9 (20-25 kDa) isolated by sodium-dodecyl sulphate-polyacrylamide gel electrophoresis showed high reciprocal antigen titer of 2048. This active antigen fraction was evaluated for its diagnostic utility in comparison with Wuchereria bancrofti microfilariae excretory-secretory antigen (Wb mf ES Ag) in inhibition ELISA. Both antigen preparations detected filarial antigen in about 80% of microfilaraemic sera, 60% chronic sera and 20-30% of endemic normal sera. This study showed that antibody and antigen isolated from hydrocele fluid were equally sensitive as FSIgG and Wb mf ES Ag in the detection of filarial antigen by inhibition ELISA. Thus hydrocele fluid may be used as an alternative source for the isolation of antibody and antigen of immunodiagnostic importance.