Protecting aquaculture by vaccinating fish Researchers with the EU-funded TARGETFISH project are using vaccines to help combat the outbreak of disease in farmed fish species. Food and Natural Resources © TARGETFISH Aquaculture production in Europe is responsible for the employment of 100 000 people, generating an annual turnover of EUR 7 billion. However, partly due to a lack of authorised veterinary products for medicinal treatment, the consequential outbreaks of disease in farmed fish species can cost the sector up to 20 % of its production value. The most appropriate method for controlling the spread of disease is to prevent it from starting in the first place, through vaccination. The EU-funded TARGETFISH project set out with one main objective: to effectively vaccinate fish. ‘TARGETFISH was revolutionary in that it not only generated fundamental knowledge for the development of next generation vaccines and different routes of vaccine administration, but it also validated this knowledge by actively working on rapid implementation of improved or new prototype vaccines,’ says Project Coordinator Geert Wiegertjes. A long-lasting contribution TARGETFISH aimed to provide a long-lasting contribution to the prevention of important fish diseases in the European aquaculture industry. Specifically, its research focused on the generation of knowledge on relevant antigens, new oral systems for delivering these antigens to mucosal body sites, and new adjuvants for improving the duration of immunity. This information was then evaluated against both mucosal and systemic protective immune responses. With this information in hand, researchers next turned their attention to learning from and improving upon, existing vaccines. They also focused on prototyping vaccines whose efficacy was then validated via in vitro assays and in vivo challenges. The efficacy of vaccines was validated for minimal side effects and maximum safety. Lastly, vaccination protocols were scrutinised under field conditions, shortening the route for the implementation of the project’s results. These results were then presented to policy makers, scientists and industry leaders. Challenges and solutions During the course of the work, researchers came up against several challenges that required innovative solutions. For example, although DNA vaccination by injection had already been shown to be effective, its application in Europe had been halted due to debates around the safety of DNA-based vaccines. ‘Knowing this, we placed substantial effort on studying the genome integration aspect, for which we expect the final data on the integration of plasmid DNA in muscle tissue in the near future,’ says Wiegertjes. ‘In the meantime, several research groups have confirmed the efficacy of this form of vaccination and, as a result, DNA vaccination against pancreas disease in Atlantic salmon may soon become a reality in Europe.’ The project also specifically aimed to integrate the many SMEs who provide improved forms of antigens, vaccination and delivery methods. One important issue addressed with the help of these enterprises was the development of oral vaccines that protect antigens from degradation in the gastro-intestinal tract. ‘Although we frequently measured a strong uptake of antigen and subsequent immune responses in the gut, we did not always find these to be protective when the fish were challenged,’ says Wiegertjes. ‘That being said, we do expect to see better protection in the future when doses and duration of feeding vaccines are optimised.’ As the project moves towards completion, it has already helped improve in-vitro read out systems and in-vivo procedures, as well as succeeding in producing improved vaccines and new vaccine prototypes. Keywords TARGETFISH, Aquaculture, fish, vaccines, antigens, pancreas disease
