Isolation of an antigen fraction from Setaria cervi adults having potential for immunodiagnosis of human filariasis.

Crude antigenic preparations from heterologous filarial parasites gave false positive results because of complex nature of these antigens and their cross-reactivity with other helminth parasites. In the present study, efforts have been made to isolate and characterize the antigens from Setaria cervi important for diagnostic purposes. The fractionation of S. cervi somatic antigenic preparation on Sephacryl S-200 resulted in separation of three major antigenic peak fractions. Crossed immunoelectrophoretic analysis, using immune rabbit serum, revealed 13-14 antigens in SFP-I pool fraction, which showed high reactivity with filarial patients sera as compared to other two pool fractions. This SFP-I fraction was further purified by DEAE-Cellulose column chromatography. Out of the 4 antigen pool fractions, DFP-IV fraction showed high ELISA reactivity with filarial patient serum pool (Wuchereria bancrofti and Brugia malayi) as compared to other fractions. The SDS-PAGE analysis of DFP-IV fraction revealed 2 major and 1 minor protein bands (mol. wt. range 65-70 kDa). Crossed immunoelectrophoresis also showed the presence of 3 antigenic peaks in DFP-IV fraction. The purified DFP-IV fraction showed high reactivity with filarial patients sera but did not cross-react with sera from ascaris and hookworm infections thereby suggesting the filaria-specificity and potential for immunodiagnosis of human filariasis.