Oral administration of recombinant outer membrane protein A-based nanovaccine affords protection against Aeromonas hydrophila in zebrafish.

Aeromonas hydrophila, an opportunistic warm water pathogen, has always been a threat to aquaculture, leading to substantial economic losses. Vaccination of the cultured fish would effectively prevent Aeromoniasis, and recent advancements in nanotechnology show promise for efficacious vaccines. Oral delivery would be the most practical and convenient method of vaccine delivery in a grow-out pond. This study studied the immunogenicity and protective efficacy of a nanoparticle-loaded outer membrane protein A from A. hydrophila in the zebrafish model. The protein was over-expressed, purified, and encapsulated using poly lactic-co-glycolic acid (PLGA) nanoparticles via the double emulsion method. The PLGA nanoparticles loaded with recombinant OmpA (rOmpA) exhibited a size of 295 ± 15.1 nm, an encapsulation efficiency of 72.52%, and a polydispersity index of 0.292 ± 0.07. Scanning electron microscopy confirmed the spherical and isolated nature of the PLGA-rOmpA nanoparticles. The protective efficacy in A. hydrophila-infected zebrafish after oral administration of the nanovaccine resulted in relative percentage survival of 77.7. Gene expression studies showed significant upregulation of immune genes in the vaccinated fish. The results demonstrate the usefulness of oral administration of nanovaccine-loaded rOmpA as a potential vaccine since it induced a robust immune response and conferred adequate protection against A. hydrophila in zebrafish, Danio rerio.

Polylactic-Co-glycolic Acid Polymer-Based Nano-Encapsulation Using Recombinant Maltoporin of Aeromonas hydrophila as Potential Vaccine Candidate.

Aquaculture production has been incurring economic losses due to infectious diseases by opportunistic pathogens like Aeromonas hydrophila, a bacterial agent that commonly affects warm water aquacultured fish. Developing an effective vaccine with an appropriate delivery system can elicit an immune response that would be a useful disease management strategy through prevention. The most practical method of administration would be the oral delivery of vaccine developed through nano-biotechnology. In this study, the gene encoding an outer membrane protein, maltoporin, of A. hydrophila, was identified, sequenced, and studied using bioinformatics tools to examine its potential as a vaccine candidate. Using a double emulsion method, the molecule was cloned, over-expressed, and encapsulated in a biodegradable polymer polylactic-co-glycolic acid (PLGA). The immunogenicity of maltoporin was identified through in silico analysis and thus taken up for nanovaccine preparation. The encapsulation efficiency of maltoporin was 63%, with an in vitro release of 55% protein in 48 h. The particle size and morphology of the encapsulated protein exhibited properties that could induce stability and function as an effective carrier system to deliver the antigen to the site and trigger immune response. Results show promise that the PLGA-mediated delivery system could be a potential carrier in developing a fish vaccine via oral administration. They provide insight for developing nanovaccine, since sustained in vitro release and biocompatibility were observed. There is further scope to study the immune response and examine the protective immunity induced by the nanoparticle-encapsulated maltoporin by oral delivery to fish.