Modulação da resposta imune inata de larvas de peixe mediante a administração in ovo de imunoestimulantes

Aquaculture has the potential to become a major food supplier in a world with an increasing human population, and increased consumption of fish will likely have positive implications on human health. The production of high-quality juveniles is still a bottleneck in the farming of numerous fish species. Survival until the juvenile stage is typically as low as 10-15% for many species. Both scientific evidence and experience in hatcheries for a variety of fish, support the hypothesis that detrimental fish–microbe interactions are the cause of these problems. Bacterial outbreaks are most commonly treated with antibiotics, but their use has become strongly regulated in many countries due to the onset and transfer of resistance mechanisms among bacteria species as well as to the bioaccumulation/biomagnification and the uncertainty of long-term effects to the environment [4]. Intensive cultivation conditions and climate change effects (rising temperature, hypoxia, salinity and acidification) may also induce stress, and thus depress larvae fish immune system. In many important cultured species such as the sea bream and sea bass, maturation of lymphomyeloid organs is delayed. Synthesis of specific antibodies is lagged until several weeks after hatching [3]. Therefore, vaccination is not an option at larval stages. Among the recommended strategies to prevent these health problems in larval cultures is the induction of larvae innate immune capacity. Synthetic CpG-ODN were among the first molecular structures explicitly designed to model the innate immune system. They have been extensively studied in different animal species including fish and shown to be capable of inducing leucocyte migration and proliferation and increase the expression of pro-inflammatory genes and genes involved in microbicidal pathways. This is encouraging for the use of CpG ODN in the prophylactic treatment of disease in fish where their biological safety and lack of unwanted side-effects following application are of great importance. In view of this, the major objective of this project is to evaluate the potential of CpG ODN to modulate the immune response in sea bass yolk-sac larvae. The aim is to stimulate the developing larval immune system at the earliest possible point in time. Therefore, we propose to explore a new and exciting approach; the delivery of CpG ODN directly to fish eggs by a bath immersion. By using a bath immersion instead of microinjection, administration of the immunostimulant can be scaled up to simultaneously treat many eggs/embryos in a highly versatile and potentially cost-effective manner suitable for its application in the industry. Deliver2Egg outputs can increase aquaculture competitiveness by improving the health and robustness of farmed fish and support green development within the sector by contributing for a reduction of prophylactic agents.