Vaccination against furunculosis and vibriosis as a model of immunization induces transcript cellular stress response in rainbow trout mucosal surfaces

Vaccination in fish evokes a stress response which may compromise its success. More knowledge about biological side effects of vaccination may aid the aquaculture industry devise effective vaccination strategies in fish to improve their effectiveness for both extracellular and intracellular agents. The aim of this study was to assess the cellular response with focus on the regulation of transcription of genes related to stress-immune responses in rainbow trout mucosal surfaces following immunization with a bivalent vaccine. Juvenile rainbow trout were vaccinated, and blood, skin, gills and intestine were sampled after 2, 8 and 12 weeks. Observed effects originate from stress pathways including neuroendocrine (gr1 and β-ar), the cutaneous CRH system (crh), cellular stress responses (cox2 and hsp70), oxidative stress (sod2 and gpx) and inflammation (il1β) markers. Gills exhibited a heightened stress response after vaccination as evidenced by significant upregulation of gr1, β-ar, crh, hsp70, cox2, myoglobin, sod2, gpx and il1β. The skin and intestine appeared to be less stressed by vaccination suggesting that these mucosal barriers are likely more resilient to stress. In addition, the majority of the measured stress-related genes followed a time-independent expression manner that suggest a long-lasting stress influence of vaccination alongside its immunogenic impact likely caused by circulating antigens. Collectively, our findings highlight the need to identify strategies to mitigate the vaccination induced-stress response in order to improve the effectiveness of fish vaccines.