Individual monitoring of salmonid immune responses during immunisation and infection

Aquaculture currently provides nearly half of all fish consumed globally and is the fastest growing sector of food and animal production. Infectious diseases are the most significant threat to the future expansion of this industry. Vaccination is widely considered the best prevention strategy and much effort is focussed upon the development of new and more efficacious fish vaccines. Most research groups use a vaccination-challenge strategy to evaluate immune protection in terminally-acquired tissue samples. However this approach requires large numbers of animals to obtain sufficient statistical power providing limited information on the kinetics of the protective response. To address this, we established a non-lethal sampling method (by withdrawing small amounts of blood repeatedly from the same individual) to monitor salmonid immunity during infection or immunisation. This enabled us to monitor (by real-time PCR) key immune markers from a small number of animals durin g pathogen challenge. Furthermore, due to the limitations of mRNA-level validation, we are currently developing a high-throughput proteomics platform to allow the rapid and accurate quantification of immune-responsive proteins in plasma samples during immunisation. Thus, we are optimising targeted and shotgun mass spectrometry approaches, performed on a Q Exactive hybrid quadrupole-Orbitrap, using rainbow trout (Oncorhynchus mykiss) as our study model. By applying a non-lethal sampling we were able to individually monitor changes in immune markers during the course of an immune response. Such information will allow a better understanding of fish immunity and might be applied in the future to reduce the number of animals required in vaccine development.