GreenOralVax brings together a multidisciplinary team that believes extracellular vesicles (EVs) are an efficient biological alternative for the protected scaffolding of proteins. The goal of GreenOralVax is therefore to develop effective and safe oral vaccines for the immunization of an economically relevant aquaculture species, the European seabass, by implementing EVs derived from non-pathogenic bacteria (cyanobacteria) as antigen delivery vehicles.
With an ever increasing demand for seafood that cannot be met by capture fisheries alone, growing pressure is being placed on aquaculture. The European seabass (ESB) is an important marine fish in Mediterranean aquaculture, with high economic impact. However, infectious diseases, such as vibriosis, photobacteriosis or tenacibaculosis are major constraints that limit ESB productivity. To meet the goal of high aquaculture production, the use of chemicals and antimicrobial drugs is common practice. Nevertheless, such chemicals can have serious detrimental impacts in the environment, and antibiotics may result in bacterial resistance.
To promote safe and effective fish growth performance strategies, new approaches are needed to safeguard fish welfare as well as the interests of farmers and consumers. Vaccination is by far the most effective and environmentally friendly solution against infectious diseases. Depending on the age and size of the fish, commercial vaccines are administered either orally, by immersion or by injection through the intraperitoneal or intramuscular route. While protection is generally highest with injection-vaccination, there is no doubt that with respect to animal welfare and handling costs, the mucosal route of vaccination, and in particular the oral route, would be the ideal method of vaccine delivery. In this context, GreenOralVax emerges to implement a novel protein carrier system based on cyanobacterial nano-sized EVs, a proprietary technology developed by members of the team, to deliver antigens orally to the ESB.
Bacterial EVs are spherical bilayered nanostructures released by the bacterial cell envelope. They naturally contain membrane and soluble proteins, lipids, and even metabolites. Release of EVs by bacterial cells represents a largely overlooked secretion mechanism, in which biologically active molecules can be trafficked to distant targets in a protected manner. As bacterial EVs are discrete and highly resistant structures, biotechnological applications have been tested, including e.g. carrying immunogenic antigens and drug delivery.
Cyanobacteria (CB) are a non-pathogenic, remarkably diverse group of bacteria, capable of producing chemical energy by harnessing solar power, which has attracted increasing attention. CB are being extensively engineered to become sustainable microbial cell factories.
Previous work by members of the GreenOralVax team showed that cyanobacterial EVs are biocompatible with fish, and that CB are amenable to engineering heterologous protein expression and loading into EVs. We demonstrated also that cyanobacterial EVs with customized protein cargo help to maintain activity of the heterologous protein, and that EVs can be ingested by fish, accumulating in the gastrointestinal tract. Moreover, we showed that intraperitoneal injection in ESB with cyanobacterial EVs loaded with a reporter protein stimulate the production of immunoglobulins.
GreenOralVax will use self-sufficient, photosynthetic bacteria to provide repetitively the desired antigen, packaged in a protective environment, without killing the producing cyanobacterium. Successful implementation of GreenOralVax will bring strong impact on reducing fish susceptibility to diseases, decreasing fish mortality, and ultimately minimizing the constraints to the development of the ESB culture sector imposed by disease outbreaks. Thus, GreenOralVax complies with Goals 2 and 14 of the UN 2030 Agenda, as it will offer an alternative for the sustainable use of marine resources, including aquaculture management. Altogether, the developed technology has commercial value and can provide significant societal benefit.
