Immune protective efficacy of recombinant vaccine against Aeromonas hydrophila secreted proteins on zebrafish

Aeromonas hydrophila is a prevalent aquatic pathogen that poses a risk to fishery production and can cause zoonotic diseases. Therefore, prevention of transmission and infection of A. hydrophila is a critical issue to address. To develop a potential subunit vaccine and provide a theoretical basis for better preventing and treating A. hydrophila disease, we selected eight secreted proteins (ORF0322, ORF3982, ORF2874, ORF1767, ORF3984, ORF2546, ORF0472 and ORF1609) from an A. hydrophila virulent strain LP-2 based on our previous research. The qPCR test shows that all selected proteins were expressed normally, then they were cloned and purified. The cloned and purified recombinant proteins were administered to zebrafish through injection. After 28 days of immunization, qPCR analysis detects increasing expression of all relevant immune genes in the zebrafish, suggesting that these recombinant proteins were capable of eliciting an immune response. In order to evaluate the immune protection offered by the eight selected secreted proteins, a bacterial challenge experiment was conducted. The results show that six of the secreted proteins (ORF3982, ORF2874, ORF1767, ORF3984, ORF0472, ORF1609) exhibited a relative immune protection rate (RPS) greater than 50%, indicating that they held promise as vaccine candidates against A. hydrophila infection.