Effects of immersion vaccination in striped catfish (Pangasianodon hypophthalmus) using a cationic lipid-based mucoadhesive nanovaccine against Edwardsiella ictaluri.

The striped catfish (Pangasianodon hypophthalmus), a commercially important aquaculture species, is severely impacted by Bacillary Necrosis of Pangasianodon (BNP), caused by Edwardsiella ictaluri, with mortality rates reaching up to 100 %. Vaccination presents a sustainable alternative to antibiotics, promoting disease control and aquaculture sustainability. This study aimed to develop a mucoadhesive chitosan-coated nanoemulsion (CS-NE) vaccine, characterize its physicochemical properties, and evaluate its efficacy against E. ictaluri. Healthy fish were immersed in either the control (unvaccinated), formalin-killed sonicated cells (FK-SC), or CS-NE for 30 min. Specific IgM levels in serum and mucus were measured up to 21 days post-vaccination (dpv), and inflammatory gene expression was assessed at 1 and 7 dpv. At 30 and 45 dpv, fish were challenged with E. ictaluri, and survival was monitored for 15 days post-challenge. The CS-NE vaccine exhibited nano-sized particles (261 nm), a positive surface charge (+32.9 mV), and a polydispersity index (PDI) < 0.3, demonstrating stability at 25 °C for 90 days. It showed enhanced gill fluorescence intensity post-immersion, significant skin penetration (80 μm at 1 min, 100 μm at 5 min), and higher relative percent survival (RPS) at 30 and 45 dpv compared to FK-SC. Additionally, CS-NE vaccination significantly elevated serum and mucus IgM levels and upregulated a2MHC and IL-1 gene expression in the gill, head kidney, and spleen, indicating enhanced immune activation. In conclusion, the CS-NE vaccine demonstrated strong potential as a cationic nanovaccine, offering effective mucosal immunization and disease prevention in striped catfish aquaculture.