Larvae and juvenile lumpfish (Cyclopterus lumpus) Immune response to oral immunization against Vibrio anguillarum

Dang, Thi Tra My (2021) Larvae and juvenile lumpfish (Cyclopterus lumpus) Immune response to oral immunization against Vibrio anguillarum. Masters thesis, Memorial University of Newfoundland.

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Abstract

Vibrio anguillarum is a common marine pathogen that causes the disease vibriosis in several finfish species, including lumpfish (Cyclopterus lumpus). The lumpfish is utilized as a cleaner fish to control sea lice in the Atlantic salmon (Salmo salar) aquaculture industry in the North Atlantic region. Lumpfish have the ability to visualize and prey upon the ectoparasite sea lice (Lepeophtheirus salmonis) found on Atlantic salmon skin. Lumpfish immunity is critical for their optimal performance and sea lice removal as they are able to significantly reduce sea lice infestations up to 93–97% on Atlantic salmon in sea pens. Oral vaccine delivery at a young age is the desired method for fish immunization. Oral vaccines are easy to use, reduce fish stress during immunization, and can be applied on a large scale while the fish are at a young age. However, the efficacy of orally delivered inactivated vaccines is controversial. In this study, I evaluated the effectiveness of a bacterin preparation against V. anguillarum orally delivered to cultured lumpfish and contrasted it to an intraperitoneal (i.p.) boost delivery. I bio-encapsulated V. anguillarum bacterin in Artemia salina (live feed) and orally immunized lumpfish larvae. The innate and adaptive immune responses of lumpfish larvae were evaluated by using real-time quantitative polymerase chain reaction (qPCR) analyses. Although the oral V. anguillarum vaccine delivered in A. salina live feed reached the lumpfish gut, real-time quantitative polymerase chain reaction (qPCR) analyses of immune-relevant transcript expression levels revealed that it only modestly immune-stimulated the lumpfish larvae. Nine months later, lumpfish were either orally, or orally and i.p boosted with the vaccine and two months later they were challenged with V. anguillarum (7.8x10⁵ CFU dose⁻¹). Oral immunization of lumpfish delayed mortality but did not confer protective immunity against the V. anguillarum challenge, which is in contrast to the i.p. vaccination which was protective.

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