Oral delivery of recombinant outer membrane protein 23-based nanovaccine can minimize Aeromonas hydrophila infection in Oreochromis niloticus.

Significant financial losses are incurred annually in commercial aquaculture due to the opportunistic pathogen Aeromonas hydrophila outbreaks in warm-water fish species. Thus, an appropriate vaccine and an efficient delivery system must be developed to combat such infectious diseases effectively. This study focused on developing an outer membrane protein (OMPs)-based nanovaccine employing the double emulsion method, integrating it in a biodegradable polylactic-co-glycolic acid (PLGA) polymer. The resultant nanoparticle, carrying the recombinant protein Omp23 (rOmp23), had a size of 346.5 nm, an impressive 74.45 % encapsulation efficiency, and a polydispersity index of 0.318. Additionally, the spherical shape of the PLGA-Omp23 nanoparticles was confirmed by scanning electron microscope. Further, to evaluate their in vivo efficacy, tilapia fish were administered the vaccine-incorporated feed orally for 21 days post-challenge with the target pathogen. Cytokine expression levels were monitored at intervals to track the activation of targeted immune genes and to assess nonspecific immune response parameters. The obtained relative percentage survival of 73 %, highlighted the therapeutic promise of the PLGA-encapsulated OMP-based nanovaccine. This study demonstrates the utility of nanoparticle system designed to encapsulate the outer membrane protein as a potential oral fish vaccine for infectious diseases. This strategy could be an efficient, cost-effective, and least stressful mode of vaccination to manage infectious diseases.