title: In vitro effects of the extracellular protein of Renibacterium salmoninarum on phagocyte function in brook trout (Salvelinus fontinalis).
abstract: Renibacterium salmoninarum is a facultative intracellular pathogen often found in host phagocytes where it appears to successfully avoid the host fish's immunological defenses. The objective of this investigation was to determine if soluble extracellular protein (ECP) produced by R. salmoninarum may contribute to the immunomodulation in bacterial kidney disease (BKD) via inhibition of phagocyte respiratory burst and/or phagocytosis mechanisms. Splenic cells from adult brook trout (Salvelinus fontinalis) were incubated with two different concentrations of ECP (0.1 mg/ml and 1.0 mg/ml) and viable R. salmoninarum. Splenic cell cultures were evaluated for respiratory burst activity via flow cytometry with the dichlorofluorescin diacetate (DCF-DA) assay and for phagocytosis via light microscopic assessment of microsphere engulfment. Respiratory burst activity was significantly inhibited in all treatment groups as compared to untreated fish, while no differences were noted in phagocytic activity.
authors.affiliation: Department of Biomedical Sciences and Pathobiology, Virginia-Maryland Regional College of Veterinary Medicine, Virginia Polytechnic Institute, Blacksburg, USA. christine_densmore@usgs.gov
authors.forename: C L
authors.initials: CL
authors.lastname: Densmore
authors.forename: S A
authors.initials: SA
authors.lastname: Smith
authors.forename: S D
authors.initials: SD
authors.lastname: Holladay
mesh_terms: D000818:Animals; D001426:Bacterial Proteins / Q000633:toxicity*; D005393:Fish Diseases / Q000209:etiology / Q000276:immunology / Q000382:microbiology; D005452:Fluoresceins; D006093:Gram-Positive Asporogenous Rods / Q000276:immunology* / Q000472:pathogenicity*; D016908:Gram-Positive Bacterial Infections / Q000209:etiology / Q000276:immunology / Q000662:veterinary; D007674:Kidney Diseases / Q000209:etiology / Q000276:immunology / Q000662:veterinary; D008863:Microspheres; D010586:Phagocytes / Q000187:drug effects* / Q000276:immunology* / Q000378:metabolism; D010587:Phagocytosis / Q000187:drug effects; D016897:Respiratory Burst / Q000187:drug effects; D013154:Spleen / Q000166:cytology / Q000276:immunology / Q000378:metabolism; D014337:Trout / Q000276:immunology* / Q000378:metabolism
chemical_list: D001426:Bacterial Proteins; D005452:Fluoresceins; C029569:diacetyldichlorofluorescein