Enhancing vibriosis vaccination in fish: genetically modified Nannochloropsis sp. as an oral vaccine carrier

Vibriosis, caused by Vibrio species, threatens marine aquaculture worldwide. Traditional vaccination methods are labor-intensive, expensive, and stressful for fish. This study investigates genetically modified Nannochloropsis sp. as a novel oral vaccine carrier against vibriosis. Using homologous recombination, nitrate reductase gene was targeted to integrate an expression cassette containing the outer membrane protein kinase (OmpK) gene from V. harveyi. Transformed microalgae were generated through electroporation and screened with bleomycin. Transgenic lines were validated at genomic, transcriptional, and translational levels. The transgenic microalgae were incorporated into fish feed to assess vaccine efficacy in fish model for infectious disease, zebrafish (Danio rerio). Immune responses were analyzed by examining IgZ, TNF-α, and IL-1β gene expression. Efficacy was evaluated through histopathology and relative percentage of survival (RPS) following bacterial challenge. Results confirmed successful transformation, with microalgae surviving bleomycin screening at 30 µgml^- 1 and exhibiting expression cassette integration via PCR and RT-PCR. Western and dot blot analyses confirmed OmpK protein expression. Vaccinated fish showed increased IgZ expression, indicating robust immune response. Fish receiving the oral vaccine achieved 90 ± 3% RPS compared to 36 ± 4.36% in controls. This approach promises to revolutionize fish vaccination, enhance aquaculture productivity, and reduce antibiotic dependence.