Location: Aquatic Animal Health ResearchTitle: Evaluation of recombinant Flavobacterium covae protein vaccines in channel catfish (Ictalurus punctatus)
|CHURCHMAN, EMILY - Auburn University
|SANKAPPA, NITHIN - Orise Fellow
|LILES, MARK - Auburn University
Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 10/30/2023
Publication Date: 11/3/2023
Citation: Churchman, E.M., Lange, M.D., Sankappa, N.M., Justice, M.E., Abernathy, J.W., Liles, M.R. 2023. Evaluation of recombinant Flavobacterium covae protein vaccines in channel catfish (Ictalurus punctatus) [ABSTRACT]. Southeastern Branch of the American Society for Microbiology Annual Meeting, Auburn, AL, November 3-5, 2023.
Technical Abstract: Columnaris disease is one of the leading causes of mortality in production of channel catfish (Ictalurus punctatus). One of the etiological agents of columnaris, Flavobacterium covae, has shown to be highly prevalent and virulent in channel catfish compared to other Flavobacterium species. As food fish production continues to increase, the frequency of columnaris disease will continue to be a major problem for the US aquaculture industry. Previous work has shown that several proteins are upregulated during biofilm formation in F. covae. Here, we test the immunogenicity and efficacy of several biofilm-associated proteins to be used as recombinant protein vaccines. The genes encoding several F. covae predicted proteins were cloned into expression vector pET-28a(+) with a C-terminal His-tag. After transformation into Escherichia coli strain BL21 (DE3), protein expression was induced with 1 mM IPTG and purified under native conditions using HisPur Ni-NTA resin. Channel catfish were injected intraperitoneally with purified protein (20 ug/mL), and peripheral blood was collected 30 days post-vaccination. Preliminary data shows vaccinated fish exhibited sera IgM antibody specificity to the respective antigens when blotted to the reduced proteins. There was a significant increase in IgM antibody titers with vaccinated fish compared to the control group. 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. There was no significant mucosal IgM antibody production among the vaccinated groups, however each vaccinated group showed significant survival when challenged with F. covae (>30% compared to the control group) at nine weeks post-immunization. Differential gene expression was identified between the adjuvant only control and vaccine groups and these results will be discussed. These results lay the groundwork for potential vaccine candidates for use as a multivalent subunit vaccine to protect farmed fish against columnaris disease during the production cycle.