Design, Construction, and Efficacy of a Novel Multiepitope Chimeric Vaccine Against Lumpfish (Cyclopterus lumpus) Infection

The development of effective vaccines is a critical step in effective disease management in aquaculture. This study introduces a novel Multiepitope Chimeric Vaccine (MCV) designed to enhance immunity in lumpfish against Vibrio anguillarum, Aeromonas salmonicida, Yersinia ruckeri, Moritella viscosa and Piscirickettsia salmonis. Epitopes from major toxins and virulence factors were selected to construct the MCV in silico. Structural validation showed 96.7% of residues in favored regions, confirming stability. Codon optimization yielded a G+C content of 54.61% and a Codon Adaptation Index (CAI) of 1, indicating strong expression potential in Escherichia coli. Immune simulations predicted robust B- and T-cell responses, suggesting induction of both humoral and cell-mediated immunity. Experimental vaccination of lumpfish (n = 35/group) with E. coli-expressed MCV led to significantly elevated IgM levels at four- and six-weeks post-vaccination (p ≤ 0.05, p ≤ 0.01, respectively). Upon pathogen challenge, vaccinated groups showed delayed mortality against V. anguillarum, A. salmonicida, and P. salmonis, though survival differences were not statistically significant across treatments. These results highlight the immunogenicity potential of the MCV and its capacity to elicit targeted immune responses. However, further optimization is necessary to improve protective efficacy and survival outcomes. This study lays a foundation for the application of multiepitope vaccines in lumpfish aquaculture and supports ongoing efforts toward sustainable disease control strategies.