Application of a Rationally Designed Mucosal Nanovaccine Platform in Bacterial Disease Prophylactics Using Fish as a...

The emergence of antimicrobial resistance necessitates innovative vaccine strategies for bacterial disease prevention in aquaculture. Here, we present a rationally designed mucosal nanovaccine platform targeting Vibrio harveyi, a major pathogen in marine fish. Bioinformatics tools identified 15 T-cell and 16 B-cell epitopes from 17 antigenic proteins, which were consolidated into a multiepitope antigen (MAE). This MAE was fused to the self-assembling ferritin H-subunit (HFn) to form MAE@HFn nanoparticles, further functionalized with PEG2000 (MAE@HFn-PEG_2k) to enhance mucus penetration. Structural characterization confirmed uniform spherical nanoparticles with high stability and negligible cytotoxicity. In marine fish models (grouper), mucosal administration of MAE@HFn-PEG_2k elicited robust humoral and cellular immune responses, including elevated IgM titers, Th1/Th2 cytokine production, and memory T-cell activation. Notably, this nanovaccine achieved an 86% survival rate post-V. harveyi challenge while overcoming traditional limitations of mucosal delivery, such as poor antigen retention. Mechanistic studies revealed efficient transepithelial transport and enhanced antigen presentation, driven by PEG-mediated mucus evasion and HFn's multivalent epitope display. This work establishes a scalable, safe, and economically viable nanoplatform for aquatic disease prophylaxis, with broader implications for mucosal vaccine design in other species.