Infectious diseases are a major constraint to the sustainable development of Aquaculture, representing economic losses of more than 10 billion USD on a global scale. The massive use of antibiotics to control fish infections has resulted in the development of resistant strains, which have rendered antibiotic treatments ineffective. Fish vaccination is a promising strategy to avoid disease outbreaks, and although already used routinely in highly produced fish species such as Atlantic salmon, their success and disease coverage is still rather limited.

In CyanoVaccine, we propose to implement outer membrane vesicles (OMV) as novel platforms in vaccine technology. The goal will be to explore OMV derived from non-pathogenic bacteria (cyanobacteria) as an antigen delivery vehicle to immunize European seabass (Dicentrarchus labrax), a marine fish economically important in Mediterranean aquaculture, against the opportunistic pathogen Mycobacterium marinum that causes mycobacteriosis, for which no vaccine or satisfactory treatment is available. CyanoVaccine will customize cyanobacterial OMV by packaging them with selected, heterologous M. marinum antigens. Engineered cyanobacterial OMV will then be administered to European seabass, stimulating specific adaptive immune responses against M. marinum antigens.
The successful implementation of CyanoVaccine will bring a strong impact on reducing fish susceptibility to diseases, decreasing fish mortality, and ultimately minimizing the constraints to the development of the sector imposed by disease outbreaks. The success achieved with this new technological approach on European seabass is expected to be easily translated to other aquaculture species. Furthermore, CyanoVaccine also holds the prospect of gaining fundamental knowledge regarding bacterial OMV structural components and biogenesis, recombinant protein expression and targeting, and physiological aspects of comparative fish immunobiology.