In PROBIOVACCINE, we propose to develop ORAL VACCINES for aquaculture. ProbioVaccine corresponds to the molecular display of antigens at the surface of spores of probiotic bacterial strains for their use as oral vaccine delivery vehicles against bacterial infectious diseases of aquatic organisms.

Oral vaccines are highly demanded by the aquaculture sector, that requests strategies for mass delivery of antigens and alternatives to the expensive and labor-intensive injectable vaccines. These later require individual handling of fish, provoking stress-related immunosuppression and mortalities. Despite this, most previous attempts to obtain effective oral vaccines in fish have failed. One possible strategy is the use of bacterial spores, extremely resistant structures with wide biotechnological applications. Bacterial spores, in particular those of Bacillus subtilis, have been shown to behave as mucosal vaccine adjuvants in mice models, but, to date, such technology has not been applied against fish bacterial diseases. To fulfill this gap, we recently developed a spore-based vaccine platform displaying an antigen against Vibriosis and, discover it to be effective in protecting the model zebrafish against 2 different problematic Vibrio pathogens. This project proposal is based on that preliminary observation and intends to generate hybrid novel products by applying the spore surface display technology at the surface of spores of probiotic Bacillus strains previously developed and patented by us for their use in fish. In this way we will create a new concept, PROBIOVACCINE, that joins the advantages of a fish specific probiotic that we own, to the oral vaccination possibilities it brings. The proposed technology has the prospect of crossing species boundaries, and thus be applied to disease control in different fish species and against different bacterial diseases affecting aquaculture sustainability. For that, the technology will be tested targeting 2 important fish pathogens with zoonotically potential, the Gram-positive Mycobacterium marinum, and the Gram-negative Vibrio anguillarum, and 2 different fish species: the fresh-water zebrafish for its importance as a model organism extensively used worldwide and especially susceptible to M. marinum outbreaks, and one of the most important aquaculture marine species, the European seabass. By providing new weapons to fight bacterial diseases, which are a bottleneck for aquaculture sustainable development and a threat to public health, this proposal will largely impact the economy and society. PROBIOVACCINE has a multidisciplinary team composed of specialists in bacteriology, microbial genetics, fish nutrition, fish physiology and fish immunology. The team is young and ambitious, complemented by senior researchers who will contribute with scientific support and project management. The collaborative network that the team has with animal nutrition & health industries, together with the team experience in turning science into IP, anticipates that at least 1 commercial product will derive from this project. PROBIOVACCINE will also generate fundamental scientific knowledge, regarding both fish immunology and mucosal vaccination, of which many aspects are still to be discovered. This is the case of mechanisms that could augment immune responses triggered by antigens allowing them to circumvent intestinal tolerance. Finally, PROBIOVACCINE is in compliance with the goals of the UN2030 agenda, promoting public health, while contributing to end hunger. Lastly, because the fish pathogens targeted in PROBIOVACCINE are emerging zoonotic agents, in the current post-antibiotic era, where the decreasing efficacy of antimicrobials might turn minor infections into global problems, this project is in line with the ONE HEALTH concept that acknowledges the interdependence of human, animal and environmental health