title: Who needs the hotspot? The effect of temperature on the fish host immune response to Tetracapsuloides bryosalmonae the causative agent of proliferative kidney disease.
abstract: Proliferative kidney disease (PKD) of salmonids, caused by Tetracapsuloides bryosalmonae may lead to high mortalities at elevated water temperatures. However, it has not yet been investigated how temperature affects the fish host immune response to T. bryosalmonae. We exposed YOY (young of the year) rainbow trout (Oncorhynchus mykiss) to T. bryosalmonae at two temperatures (12 °C and 15 °C) that reflect a realistic environmental scenario and could occur in the natural habitat of salmonids. We followed the development of the parasite, host pathology and immune response over seven weeks. We evaluated the composition and kinetics of the leukocytes and their major subgroups in the anterior and posterior kidney. We measured immune gene expression profiles associated with cell lineages and functional pathways in the anterior and posterior kidney. At 12 °C, both infection prevalence and pathogen load were markedly lower. While the immune response was characterized by subtle changes, mainly an increased amount of lymphocytes present in the kidney, elevated expression of Th1-like signature cytokines and strong upregulation of the natural killer cell enhancement factor, NKEF at week 6 P.E. At 15 °C the infection prevalence and pathogen burden were ominously greater. While the immune response as the disease progressed was associated with a Th2-like switch at week 6 P.E and a prominent B cell response, evidenced at the tissue, cell and transcript level. Our results highlight how a subtle, environmentally relevant difference in temperature resulted in diverse outcomes in terms of the immune response strategy, altering the type of interaction between a host and a parasite.
authors.affiliation: University of Berne, Vetsuisse Faculty, Centre for Fish and Wildlife Health, Länggassstrasse 122, CH-3012 Berne, Switzerland.
authors.forename: Christyn
authors.initials: C
authors.lastname: Bailey
authors.affiliation: University of Berne, Vetsuisse Faculty, Centre for Fish and Wildlife Health, Länggassstrasse 122, CH-3012 Berne, Switzerland.
authors.forename: Helmut
authors.initials: H
authors.lastname: Segner
authors.affiliation: University of Berne, Vetsuisse Faculty, Centre for Fish and Wildlife Health, Länggassstrasse 122, CH-3012 Berne, Switzerland.
authors.forename: Ayako
authors.initials: A
authors.lastname: Casanova-Nakayama
authors.affiliation: University of Berne, Vetsuisse Faculty, Centre for Fish and Wildlife Health, Länggassstrasse 122, CH-3012 Berne, Switzerland. Electronic address: thomas.wahli@vetsuisse.unibe.ch.
authors.forename: Thomas
authors.initials: T
authors.lastname: Wahli
mesh_terms: D000818:Animals; D005260:Female; D005393:Fish Diseases / Q000276:immunology* / Q000469:parasitology; D007113:Immunity, Innate; D007674:Kidney Diseases / Q000276:immunology / Q000469:parasitology / Q000662:veterinary*; D055764:Myxozoa / Q000502:physiology*; D017686:Oncorhynchus mykiss; D010273:Parasitic Diseases, Animal / Q000276:immunology* / Q000469:parasitology; D016133:Polymerase Chain Reaction / Q000662:veterinary; D013696:Temperature
keywords: Immune response; PKD; Proliferative kidney disease; Rainbow trout; Resistance; Temperature; Tetracapsuloides bryosalmonae; Th1; Th2; Tolerance