A BCWD-Resistant line of rainbow trout is less sensitive to cortisol implant-induced changes in IgM response as compared to a susceptible (control) line. (March 2021)

• Record Type: Journal Article
• Authors: Quddos, Fatima; Zwollo, Patty
• Is Part Of: Developmental and comparative immunology. Volume 116(2021)
• Publication Date: 2021-03
• Subjects: Rainbow trout -- Immunoglobulin heavy chain mu and tau -- Chronic stress -- Cortisol -- Flavobacterium psychrophilum -- In vivo challenge; Fp Flavobacterium psychrophilum -- RBT Rainbow trout -- memHC mumembrane heavy chain mu -- secHC Musecreted heavy chain mu -- L Line -- TG treatment group -- DPI Days Post Infection -- PBL Peripheral blood leukocyte -- BCWD Bacterial Cold Water Disease -- R-line Fp-resistant Line -- S-line Fp-susceptible line; Immunology -- Periodicals; Developmental immunology -- Periodicals; 616.079
• DOI: 10.1016/j.dci.2020.103921
• Languages: English
• ISSNs: 0145-305X

Abstract

Abstract: In salmonids, stress responses increase cortisol levels and disease susceptibility, including to Flavobacterium psychrophilum (Fp), the causative agent of BCWD. A BCWD-resistant line (R-line) of rainbow trout was used here to investigate potential differences in immunoglobulin response after a combined treatment of cortisol and Fp, as compared to a susceptible (S-line) control line. Expression of membrane and secreted immunoglobulin heavy chains mu and tau were determined by RT-qPCR in spleen and anterior kidney. Cortisol treatment did not affect B cell development in the anterior kidney, but delayed IgM responses at the early stage of infection in the spleen of both lines. An earlier IgM response was a determining factor in differential disease progression between resistant- and susceptible fish after Fp -challenge. S-line fish had a delayed and exacerbated IgM response after cortisol implant indicative of a detrimental cycle of sustained IgM responses and high pathogen loads. In contrast, R-line fish had delayed but milder, and protective IgM responses and cleared pathogen successfully. Fp challenge after cortisol implant increased serum cortisol levels on days 3 and 5 compared to mock treatments in S-line fish, but only on day 3 in R-line. Hence, combined cortisol treatment and Fp challenge differentially modulated B cell activation and Fp loads in BCWD-resistant and susceptible lines of rainbow trout. We propose that under conditions of increased stress, BCWD-resistant fish may remain immunologically better equipped to respond to infections compared to BCWD susceptible fish. Highlights: Cortisol implants delayed IgM response and effected pathogen clearance more strongly in BCWD-susceptible fish. BCWD-susceptible fish had stronger correlations between IgM response, cortisol and pathogen load. Pathogen-challenge lowered PBL cell density but only in BCWD-susceptible fish. BCWD-resistant fish were less sensitive to cortisol implants then -susceptible fish.