In situ mineralization of nano-selenium onto inactivated LMBV to enhance immune protection against viral infection.

Largemouth bass ranavirus (LMBV) is a major viral pathogen threatening the sustainable development of the largemouth bass (Micropterus salmoides) aquaculture industry. However, conventional inactivated vaccines generally exhibit limited immunogenicity and insufficient immune protection. Herein, a nano-selenium-functionalized inactivated vaccine (SeNPs/LMBV inactivated vaccine) was successfully constructed through an in situ mineralization strategy, in which selenium ions were initially assembled onto the surface of inactivated LMBV particles through electrostatic interactions and subsequently reduced into elemental selenium nanoparticles. Transmission electron microscopy revealed that selenium nanoparticles with sizes of approximately 20-50 nm were uniformly assembled on the surface of inactivated LMBV particles, forming a stable nano-bio interface structure. The obtained SeNPs/LMBV inactivated vaccine exhibited significant superoxide dismutase (SOD)-like and catalase (CAT)-like antioxidant activities, indicating potent antioxidant capacity. Biosafety evaluations demonstrated that the SeNPs/LMBV inactivated vaccine caused no obvious cytotoxicity or histopathological damage at the experimental dosage, suggesting favorable biocompatibility. Moreover, immunization with the SeNPs/LMBV inactivated vaccine significantly enhanced serum neutralizing antibody titers and upregulated the expression of immune-related genes, including TNF-α, IL-1β, IFN-γ, and IgM, compared with the conventional inactivated vaccine. Following lethal LMBV challenge, the relative percent survival (RPS) of the SeNPs/LMBV-immunized group reached 77.5%. Collectively, these findings demonstrate that in situ mineralization of nano-selenium can effectively enhance the immune protective efficacy of inactivated LMBV vaccines, providing a promising strategy for the prevention and control of LMBV infection and highlighting the potential application of nano-selenium adjuvants in aquatic viral vaccines.