A study conducted by Portuguese researchers, in collaboration with Spanish colleagues, has shown that Bacillus subtilis spores can be “effective as antigen vectors for the administration of oral vaccines in fish, both marine and freshwater, both in the larval stage. than in the fry “. .
As explained in an article recently published in the scientific journal Frontiers in immunologyOral vaccines are in high demand in fish farming because they are much cheaper than injectable vaccines which require a lot of work, require individualized handling of the fish and produce stress in them, causing mortality.
The strategy of delivering antigens to fish through vectors using bacterial spores, EsporoVacunas, has been under consideration for some time. These spores are extremely resistant with wide biotechnological applications, including as probiotics, visualization systems or adjuvants, substances that increase or modulate the immune response of a vaccine.
The study was conducted by researchers from the Interdisciplinary Center for Marine and Environmental Research of the University of Porto (CIIMAR-UP), where colleagues from the NOVA University of Lisbon, the Institute of Chemical and Biological Technology António Xavier de Oeiras and the INIA-CSIC Group of Fish Immunology and Pathology in Spain.
As they point out, in the particular case of Bacillus subtilis spores, they have been observed to behave as mucosal vaccine adjuvants in mouse models. However, until now this technology has not been tested on bacterial fish diseases.
The experimental animal models were zebrafish (Denmark rerio), a freshwater species, and the European sea bass (Dicentrarchus labrax), of sea water. They dealt with vibriosis, an infection caused by The vibration of the eels and from Vibrio parahaemolyticus.
For the study, the researchers used a strain of A thin bacillus manipulated in the laboratory to display a Vibrio antigenic protein, OmpK, or the green fluorescent protein GFP on the surface of its spores.
In the case of zebrafish, diving with OmpK-carrying spores survives after a bacterial challenge with V. eels y V. parahaemolyticus increase between 50 and 90%, depending on the target pathogen.
In the case of sea bass, several results have been achieved. First, as they point out, anti-GFP antibodies could be detected in the serum of juveniles fed diets containing OmpK-carrying spores. More importantly, they note, sea bass survival increased from 60 to 86 percent when previously vaccinated orally.
