AUTHOR=Gonçalves Gabriela , Santos Rafaela A. , Coutinho Filipe , Pedrosa Neide , Curado Maria , Machado Marina , Costas Benjamin , Bonneville Lourenço , Serrano Mónica , Carvalho António Paulo , Díaz-Rosales Patricia , Oliva-Teles Aires , Couto Ana , Serra Cláudia R. 

TITLE=Oral vaccination of fish against vibriosis using spore-display technology

JOURNAL=Frontiers in Immunology

VOLUME=13

YEAR=2022

URL=https://www.frontiersin.org/journals/immunology/articles/10.3389/fimmu.2022.1012301

DOI=10.3389/fimmu.2022.1012301

ISSN=1664-3224

ABSTRACT=<p>Oral vaccines are highly demanded by the aquaculture sector, to allow mass delivery of antigens without using the expensive and labor-intensive injectable vaccines. These later require individual handling of fish, provoking stress-related mortalities.</p><p>One possible strategy to create injection-free vaccine delivery vehicles is the use of bacterial spores, extremely resistant structures with wide biotechnological applications, including as probiotics, display systems, or adjuvants. Bacterial spores, in particular those of <italic>Bacillus subtilis</italic>, have been shown to behave as mucosal vaccine adjuvants in mice models. However, such technology has not been extensively explored against fish bacterial disease.</p><p>In this study, we used a laboratory strain of <italic>B. subtilis</italic>, for which a variety of genetic manipulation tools are available, to display at its spores surface either a <italic>Vibrio</italic> antigenic protein, OmpK, or the green fluorescence protein, GFP. When previously vaccinated by immersion with the OmpK- carrying spores, zebrafish survival upon a bacterial challenge with <italic>V. anguillarum</italic> and <italic>V. parahaemolyticus</italic>, increased up to 50 - 90% depending on the pathogen targeted. Further, we were able to detect anti-GFP-antibodies in the serum of European seabass juveniles fed diets containing the GFP-carrying spores and anti-<italic>V. anguillarum</italic> antibodies in the serum of European seabass juveniles fed the OmpK-carrying spores containing diet. More important, seabass survival was increased from 60 to 86% when previously orally vaccinated with in-feed OmpK- carrying spores. Our results indicate that <italic>B. subtilis</italic> spores can effectively be used as antigen-carriers for oral vaccine delivery in fish.</p>