Comparative analysis of immunoglobulin molecules from catfish, Clarias batrachus, Clarias gariepinus and C. batrachus♀ x C. gariepinus ♂ hybrid

Knowledge on the immunoglobulin molecules of teleosts is important in devising appropriate strategies for diagnosis and control of infectious diseases. In the present investigation, a comparative study of immunoglobulin molecules from Clarias batrachus, Clarias gariepinus and their F-1 hybrid (C. batrachus female x C. gariepinus male) was undertaken to determine the size variations among these molecules and to assess their antigenic relatedness. The fishes were immunised with bovine serum albumin (BSA) and immunoglobulin molecules were purified from the immune serum of each species by affinity chromatography using BSA-Sepharose 4B. Native PAGE analysis of the purified immunoglobulins exhibited single band corresponding to a molecular weight of 863 kDa for C. batrachus, 864 kDa for the hybrid and 860 kDa for C. gariepinus, respectively. Two heavy (H) chains of similar to 66 and similar to 59 kDa, similar to 76 and similar to 66 kDa, similar to 86 and similar to 72 kDa, respectively for these species were identified by SDS-PAGE. However, there were two light (L) chain bands for C. batrachus and hybrid with molecular weights of similar to 27 and similar to 26 kDa, and one for C. gariepinus with a molecular weight of similar to 27 kDa. Western blot analysis using rabbit anti-C.batrachus Ig serum was shown to react with immunoglobulins of C. batrachus as well as the hybrid indicating their relatedness but not with the immunoglobulin of C. gariepinus. The study further indicated that the polyclonal antibody developed for C. batrachus can effectively be used to study the immune response in the hybrid catfish but not in C. gariepinus.