Characterization of serum immunoglobulin in channa striata (BLOCH) and kinetics of its response to Aeromonas hydrophila antigen.

The immunoglobulin (Ig) from the serum of Channa striata was isolated by gel electroelution and characterized further to understand its nature and subsequent applications in studying the immune response. The purity of the sample was confirmed with the presence of a single band on native gradient PAGE and the molecular weight of ∼897 kDa was determined from the gel. In SDS-PAGE, C. striata Ig was reduced to produce two bands corresponding to H (heavy) (∼72 kDa) and L (light) (∼27 kDa) chain subunits. Polyclonal antiserum against the purified Ig was raised in a rabbit and adsorbed with 10% liver tissue homogenate of C. striata to enhance its specificity. By an indirect ELISA standardized using the adsorbed rabbit antiserum, the normal serum Ig concentration in C. striata was estimated to be 3.48 mg/mL. Further, a kinetic study of specific immunoglobulin response to formalin-killed Aeromonas hydrophila antigen was undertaken using another indirect ELISA, which showed a significant increase in serum immunoglobulin titer from day 2 onwards and reached its peak at day 14. Subsequently, the Ig titer was dropped from day 21 onwards till the completion of the experiment at day 42, although it was at a significantly higher level than the control.