Fishing for Protection: Evaluating Recombinant Flavobacterium covae Vaccines in Channel Catfish 3683

Description Columnaris disease, caused by Flavobacterium covae, is one of the leading causes of mortality in channel catfish and leads to ∼$11 million dollars in annual production losses. Here, we test the immunogenicity and efficacy of two F. covae proteins associated with bacterial biofilms that were evaluated as recombinant subunit vaccines. The antigens were cloned and expressed in E. coli, then purified under native conditions. Channel catfish intraperitoneally injected with purified protein (20 ug/mL) and commercial adjuvant exhibited sera IgM antibody specificity to the respective antigens 30 days post-vaccination. In our next trial, groups of fish (n = 540) were immunized by bath immersion with the recombinant protein(s) (1 ug/mL) or sham immunized. Each vaccinated group showed significant survival when challenged with F. covae (>30% compared to the control group) at nine weeks post-immunization. While no antigen-specific skin mucosal IgM antibodies were detected via ELISA, significant upregulation of T-cell associated genes by RT-qPCR was seen in one vaccine group. The efficacy of the vaccine(s) delivered orally via top-coating feed with or without a dietary Bacillus probiotic will be discussed as well. These results lay the groundwork for potential vaccine candidates to protect farmed fish against columnaris disease during the production cycle. Funding Sources This project was supported through USDA NIFA predoctoral fellowship under ALA021-4-19194. Topic Categories Veterinary and Comparative Immunology (VET)