Development and Initial Testing of Diatom-Based Self-adjuvanting Antigen-Adjuvant Fusion Subunit Protein Oral Vaccines against Piscine Francisellosis in Nile Tilapia

PROJECT SUMMARYDevelopment and Initial Testing of Diatom-Based Self-adjuvanting Antigen-AdjuvantFusion Subunit Protein Oral Vaccines against Piscine Francisellosis in Nile TilapiaProject Director: Shrestha Roshan P.Institution: PhycoVax LLCSub-awardee/Co-PI: Soto EstebanInstitution: University of California DavisGram-negative bacterium Francisella orientalis the etiologic agent of piscine francisellosisinfects various freshwater and marine fish species worldwide. In the USA the disease causeshigh mortalities in tilapia and other warm-water fishes including ornamental cichlidslargemouth bass hybrid striped bass French grunts and Caesar grunts. Lack of sensitivediagnostic tests approved treatments and vaccines in the U.S. aquaculture industry have resultedin over 90% mortalities in some cases. Economic losses from francisellosis result directly fromfish mortalities and through delayed production and growth added labor costs and potentialtreatment expenditures over time. While antibiotics are still used to treat bacterial diseasestreatments often fail for lack of ingestion by anorectic fish. On the other hand the release ofantibiotics into natural habitats poses a potential environmental threat. Thus disease preventionthrough vaccination is preferred over antibiotics treatment. Costs and the efficacy of availablevaccines against intracellular pathogens have been challenging for the aquaculture industry. Withtools and techniques developed by PhycoVax and the expertise of a collaborating partner at theUniversity of California Davis this project proposes investigating the potential use of algae- based subunit vaccines to protect Nile tilapia against piscine francisellosis. The efficacy of afeed-based vaccine will be investigated by feeding whole diatom cells expressing antigen- adjuvant fusion protein to na¯ve tilapia fingerlings. A successful development of algae-based oralaquaculture vaccines will open the door to rapid generation of novel cost-effective fish vaccinesresulting in improved aquaculture health and productivity of the U.S. aquaculture industry.