Modification of a DNA Vaccine for Oral Administration in Fish for Aquaculture by Using Non-Microbial Nanoparticles

Utilization of DNA vaccines in aquaculture has been gaining interest and recent efforts have been focused on methods of delivering DNA vaccines to fish. In the present study, a methodology was sought that could protect DNA vaccines such that they could be orally administered. The main objective of the study was to determine if a DNA vaccine could be effectively compounded into an orally administrable formulation with chitosan or polylactide-co-glycolide (PLG). The immune response of hybrid striped bass (Morone saxatilis x Morone chrysops) following oral delivery of a DNA vaccine containing Mycobacterium marinum Ag85A plasmid in either chitosan or PLG nanoparticle encapsulation was evaluated. Hybrid striped bass were divided into four experimental groups: IM immunization of the DNA vaccine as a positive control, oral delivery of uncomplexed DNA vaccine, oral delivery of chitosan or PLG alone as a negative control, and oral delivery of complexed chitosan or complexed PLG DNA vaccine. Fish were bled at regular intervals and an ELISA was used to evaluate antibody levels in individual fish. While the chitosan /plasmid DNA complex containing the Mycobacterium marinum Ag85A gene failed to produce a significant antibody response, the PLG/plasmid DNA matrix stimulated humoral immune response in the fish.