Evaluation of the vaccine formulation with recombinant protein CP01850 and fish oil from Rhamdia quelen: an alternative and innovative adjuvant against Corynebacterium pseudotuberculosis.

Fish oils contain bioactive molecules such as omega-3, -6, and - 9 fatty acids, which modulate immune responses. The oil of Rhamdia quelen (RQO) was characterized, revealing 62.86% unsaturated fatty acids. To assess its potential as an adjuvant in caseous lymphadenitis (CLA) vaccines, Balb/c mice were divided into four groups: saline (G1), rCP01850 + AddaVax (G2), rCP01850 + RQO (G3), and RQO alone (G4). Only G3 achieved significant protection (4/10, p = 0.0047), while G1 and G4 showed none. Humoral analysis showed that G3 had the second highest antibody production (total IgG, IgG2b, IgG3), surpassed only by G2. At day 42, IgG1 and IgG2a levels were statistically equivalent between G2 and G3. Importantly, G3 was the only group with elevated IFN-γ and IL-17 (p = 0.0001), indicating a robust cellular immune response. These findings suggest that RQO is a safe and promising natural adjuvant capable of enhancing both humoral and cellular responses, improving vaccine efficacy against CLA.