Sea Bass Immunization to Downsize the Betanodavirus Protein Displayed in the Surface of Inactivated Repair-Less...

: This work describes immunization of European sea bass (Dicentrarchus labrax) juveniles against viral nervous necrosis virus (VNNV), a betanodavirus causing worldwide mortalities in many fish species. Protection was obtained with the so-called spinycterin vehicles consisting of irreversibly DNA-damaged DNA-repair-less Escherichia coli displaying at their surface a downsized VNNV coat antigen. In this work we have i) maximized bacterial expression levels by downsizing the coat protein of VNNV to a fragment (frgC_91-220) containing most of its previously determined antigenicity, ii) developed a scalable autoinduction culture media for E.coli based in soy-bean rather than in casein hydrolysates, iii) enriched surface expression by screening different anchors from several prokaryotic sources (anchor + frgC_91-220 recombinant products), iv) preserved frgC_91-220 antigenicity by inactivating bacteria by irreversible DNA-damage by means of Ciprofloxacin, and v) increased safety using a repair-less E.coli strain as chassis for the spinycterins. These spinycterins protected fish against VNNV challenge with partial (Nmistic + frgC_91-220) or total (YBEL + frgC_91-220) levels of protection, in contrast to fish immunized with frgC_91-220 spinycterins_. The proposed spinycterin platform has high levels of environmental safety and cost effectiveness and required no adjuvants, thus providing potential to further develop VNNV vaccines for sustainable aquaculture.