Immunogenicity and protective efficacy of a native omp34 subunit vaccine against Aeromonas hydrophila in BALB/c mice: Identification of nitroblue tetrazolium as a correlate of protection within a One Health framework

The nOmp34 subunit vaccine elicited a strong, coordinated humoral and innate immune response, surpassing the matched bacterin in both efficacy and immune strength. NBT activity between days 35-42 proved to be a practical indicator of protection, aligning mechanistically with nicotinamide adenine dinucleotide phosphate -oxidase-mediated bacterial killing. These findings offer proof-of-concept for Omp34 as a scalable, antibiotic-sparing vaccine candidate and support its progression into aquaculture-relevant platforms within a One Health framework.