Characterization of immunoreactive proteins of Setaria cervi isolated by preparative polyacrylamide gel electrophoresis.

Filarial parasites are complex mixtures of antigenic proteins and characterization of these antigenic molecules is essential to identify the diagnostically important filaria-specific antigens. In the present study, we have fractionated the somatic extracts from adults of Setaria cervi (bovine filarial parasite) on preparative SDS-polyacrylamide gel electrophoresis and tested the immunoreactivity of the separated gel fractions with polyclonal antibodies against filarial excretory-secretory antigens as well as filarial patients sera. The SDS-PAGE analysis of gel eluted fractions revealed 1 protein band in F-1 fraction, 2 protein bands in F-2 fraction and 2-3 protein bands in all other fractions (F3- F11). Seven gel eluted fractions (F1, F2, F3, F4, F5, F6 and F11) showed high ELISA reactivity with the polyclonal antibody (against excretory-secretory antigen) and four of these fractions (F-1, F-2, F3 and F6) exhibited high ELISA reactivity with antibodies present in filarial patient sera. The reactivities of the gel fractions (F1 and F2), recognized by filarial patients sera, were also tested with the monoclonal antibody (detecting the filarial circulating antigen). The F1 and F2 gel eluted fractions were found to have the target antigen of monoclonal antibody as evident by high reactivity with the monoclonal antibody in ELISA and immunoblotting. The S. cervi gel eluted F1 fraction (containing single antigen) could detect antibodies in filarial patients sera and not in non-filarial sera thereby suggesting its usefulness for specific serodiagnosis of human filariasis.