Submitted to: Veterinary Immunology and Immunopathology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/4/1997
Publication Date: N/A
Citation: Interpretive Summary: Edwardsiella ictaluri is a major cause of economic losses in the catfish industry. Little is known about immune responses, especially by the skin of catfish. We developed an immunoassay to quantify immunoglobulin (antibody) in the serum and mucus. Our results indicate that the skin of catfish is part of its immune system. We also demonstrated that some infected catfish produce excessive amounts of serum antibody. This finding is important to understanding the pathology of enteric septicemia of catfish and the development of vaccines.
Technical Abstract: An immunoassay was developed to quantify immunoglobulin (Ig) in the serum and mucus of channel catfish. The Falcon Assay Screening Test (FAST) enzyme-linked immunosorbent assay (ELISA) beads were sensitized with serum or mucus samples and their Ig levels quantified with goat anti-catfish Ig and mouse anti-goat Ig conjugate. Coefficients of intra- and interassay variations of 1.7 to 12.4% and 1.5 to 10.2% respectively, indicated that the assay was highly reproducible. Serum Ig concentration was found to increase from 1.44 + 0.56 to 42.3 + 48.43 mg m1-1 between 3 and 15 months of age. In contrast, mucus Ig concentration slightly decreased from 16.0 + 10 to 11.0 + 2 ng cm-2 of skin between 3 and 15 months of age. Fish to fish variability for Ig concentrations increased with age in sera (42.3 + 48.43 mg m1-1), but not in mucus (11.0 + 0.2 ng cm-2. The kinetics of Ig production following infection with Edwardsiella ictaluri showed that serum Ig concentrations peaked (846.6 + 1850 mg m1-1) at 34 days post-infection. The mucus Ig concentrations peaked 7 days before at 768.0 + 1821.0 ng cm-2. The results suggest that E. ictaluri infection causes excessively higher Ig production than that found in non-infected fish of the same age. Our results show differences in serum and mucus Ig concentrations with age and after infection with E. ictaluri.