Preliminary Immunological Evaluation of Alginate Microparticles Loaded with Recombinant VP2 as an Immersion-Delivered Antigen Against Infectious Pancreatic Necrosis Virus (IPNV) in Salmonids.

Infectious pancreatic necrosis (IPN) is a highly contagious viral disease that causes significant economic losses in the global salmon farming industry. Despite the widespread use of vaccines, outbreaks caused by infectious pancreatic necrosis virus (IPNV) continue to occur, even in genetically resistant fish populations. Therefore, the development of alternative vaccination strategies remains a priority for sustainable aquaculture. In this study, we developed a vaccine prototype based on the recombinant IPNV capsid protein VP2 loaded in alginate microparticles for immersion immunization. The VP2 protein was produced using the E. coli pET21b+ expression system and subsequently encapsulated in alginate by ionic gelation with calcium chloride. The immunogenic potential of the VP2-MP formulation was evaluated in salmonids by quantifying specific antibody levels and analyzing the transcription of immune-related genes (ifn-α, ifn-γ, mx, and tbet). Fish immunized with VP2-MP showed induction of antiviral immune responses characterized by increased expression of ifn-γ and mx, together with detectable levels of specific antibodies against IPNV-VP2. Overall, these results indicate that alginate microparticles enhance the immunogenicity of the VP2 antigen and support the feasibility of immersion-based vaccination strategies against IPNV in salmonids.