Oral Immunization of Larvae and Juvenile of Lumpfish (Cyclopterus lumpus) against Vibrio anguillarum Does Not Influence Systemic Immunity

Abstract

Vibrio anguillarum, a marine bacterial pathogen that causes vibriosis, is a recurrent pathogen of lumpfish (Cyclopterus lumpus). Lumpfish is utilized as a cleaner fish in the Atlantic salmon (Salmo salar) aquaculture in the North Atlantic region because of its ability to visualize and prey on the ectoparasite sea lice (Lepeophtheirus salmonis) on the skin of Atlantic salmon, and its performance in cold environments. Lumpfish immunity is critical for optimal performance and sea lice removal. Oral vaccine delivery at a young age is the desired method for fish immunization because is easy to use, reduces 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, we evaluated the effectiveness of a V. anguillarum bacterin orally delivered to cultured lumpfish and contrasted it to an intraperitoneal (i.p.) boost delivery. We bio-encapsulated V. anguillarum bacterin in Artemia salina live-feed and orally immunized lumpfish larvae. Vaccine intake and immune response were evaluated by microscopy and quantitative polymerase chain reaction (qPCR) analysis, respectively. qPCR analyses showed that the oral immunization of lumpfish larvae resulted in a subtle stimulation of canonical immune transcripts such as il8b, il10, igha, ighmc, ighb, ccl19, ccl20, cd8a, cd74, ifng, and lgp2. Nine months after oral immunization, one group was orally boosted, and a second group was both orally and i.p. boosted. Two months after boost immunization, lumpfish were challenged with V. anguillarum (7.8 × 105 CFU dose−1). Orally boosted fish showed a relative percentage of survival (RPS) of 2%. In contrast, the oral and i.p. boosted group showed a RPS of 75.5% (p < 0.0001). V. anguillarum bacterin that had been orally delivered was not effective in lumpfish, which is in contrast to the i.p. delivered bacterin that protected the lumpfish against vibriosis. This suggests that orally administered V. anguillarum bacterin did not reach the deep lymphoid tissues, either in the larvae or juvenile fish, therefore oral immunization was not effective. Oral vaccines that are capable of crossing the epithelium and reach deep lymphoid tissues are required to confer an effective protection to lumpfish against V. anguillarum

Characterization of miRNAs in Embryonic, Larval, and Adult Lumpfish Provides a Reference miRNAome for Cyclopterus lumpus

“…Additionally, lumpfish embryos (300 degree days) and lumpfish larvae (one week posthatch) were obtained from the JBARB. Lumpfish egg masses were fertilized and maintained with flow-through in 5 L upwelling black nontranslucent incubators at 8–10 °C supplied with 95–110% air saturated and 5 µm UV-treated filtered flow-through seawater (spring–summer) [ 45 ]. After completing the development of the embryo, the larvae hatch are maintained at 10 °C [ 46 ].…”

Pathogenic Photobacterium sp. induce mortality in the lined seahorse (Hippocampus erectus): First case report from China

“…Many Vibrio sp. bacteria, such as V. anguillaru, V. parahaemolyticus, V. alginolyticus, V. vulnificus, and V. harveyi, can cause fish diseases, resulting in significant economic losses (Dang et al, 2021;Lazarte et al, 2021;Sony et al, 2021). However, except for Photobacterium damselae, there are few reports of the genus Photobacterium as a fish pathogen (Liu et al, 2003;Wang et al, 2007).…”

Haemato-Immunological Response of Immunized Atlantic Salmon (Salmo salar) to Moritella viscosa Challenge and Antigens

“…Bacterial cell count was measured after 72 h incubation at 15 • C [37]. After counting, the bacterial cells were inactivated by adding 6% (v/v) of formalin (Sigma Chemical, St. Louis, MO, USA) and incubated at 4 • C for 48 h. Formaldehyde was removed by centrifugation, the cells were washed three times with PBS 1X, and then the cells were dialyzed (Spectrum™ Spectra/Por™ dialysis membrane; 12-14,000 Dalton molecular weight cut-off; Thermo Fisher, USA) in 1 L PBS 1X at 4 • C for 24 h with agitation in an orbital shaker [43]. M. viscosa inactivation was confirmed by plating onto TSA 2% NaCl for 24 h at 15 • C. The final concentration of bacterin (4.1 × 10 8 CFU/mL) was determined by a flow cytometer (Figure S2A) [44,45].…”