title: β-Glucan-supplemented diets increase poly(I:C)-induced gene expression of Mx, possibly via Tlr3-mediated recognition mechanism in common carp (Cyprinus carpio).
abstract: We have previously observed that in common carp (Cyprinus carpio), administration of β-glucan (MacroGard®) as feed additive leads to a lower expression of pro-inflammatory cytokines suggesting that this immunostimulant may be preventing an acute and potentially dangerous response to infection, particularly in the gut. However, in general, mechanisms to detect and eliminate pathogens must also be induced in order to achieve an efficient clearance of the infection. Protection against viral diseases acquired through β-glucan-supplemented feed has been extensively reported for several experimental models in fish but the underlining mechanisms are still unknown. Thus, in order to better characterize the antiviral action induced by β-glucans in fish, MacroGard® was administered daily to common carp in the form of supplemented commercial food pellets. Carp were fed for a period of 25 days prior to intra-peritoneal injection with polyinosinic:polycytidylic acid (poly(I:C)), a well-known double-stranded RNA mimic that triggers a type-I interferon (IFN) response. Subsequently, a set of immune related genes, including mx, were analysed by real-time PCR on liver, spleen, head kidney and mid gut tissues. Results obtained confirmed that treatment with β-glucan alone generally down-regulated the mRNA expression of selected cytokines when compared to untreated fish, while mx gene expression remained stable or was slightly up-regulated. Injection with poly(I:C) induced a similar down-regulated gene expression pattern for cytokines in samples from β-glucan fed fish. In contrast, poly(I:C) injection markedly increased mx gene expression in samples from β-glucan fed fish but hardly in samples from fish fed control feed. In an attempt to explain the high induction of mx, we studied Toll-like receptor 3 (TLR3) gene expression in these carp. TLR3 is a prototypical pattern recognition receptor considered important for the binding of viral double-stranded RNA and triggering of a type-I IFN response. Through genome data mining, two sequences for carp tlr3 were retrieved (tlr3.1 and tlr3.2) and characterized. Constitutive gene expression of both tlr3.1 and tlr3.2 was detected by real-time PCR in cDNA of all analysed carp organs. Strikingly, 25 days after β-glucan feeding, very high levels of tlr3.1 gene expression were observed in all analysed organs, with the exception of the liver. Our data suggest that β-glucan-mediated protection against viral diseases could be due to an increased Tlr3-mediated recognition of ligands, resulting in an increased antiviral activity of Mx.
authors.affiliation: School of Life Sciences, Keele University, Keele, Staffordshire ST5 5BG, United Kingdom; Cell Biology and Immunology Group, Wageningen Institute of Animal Sciences, Wageningen University, P.O. Box 338, Wageningen 6700 AH, The Netherlands.
authors.forename: Alberto
authors.initials: A
authors.lastname: Falco
authors.affiliation: School of Life Sciences, Keele University, Keele, Staffordshire ST5 5BG, United Kingdom.
authors.forename: Joanna J
authors.initials: JJ
authors.lastname: Miest
authors.affiliation: School of Life Sciences, Keele University, Keele, Staffordshire ST5 5BG, United Kingdom.
authors.forename: Nicolas
authors.initials: N
authors.lastname: Pionnier
authors.affiliation: Cell Biology and Immunology Group, Wageningen Institute of Animal Sciences, Wageningen University, P.O. Box 338, Wageningen 6700 AH, The Netherlands.
authors.forename: Danilo
authors.initials: D
authors.lastname: Pietretti
authors.affiliation: Cell Biology and Immunology Group, Wageningen Institute of Animal Sciences, Wageningen University, P.O. Box 338, Wageningen 6700 AH, The Netherlands.
authors.forename: Maria
authors.initials: M
authors.lastname: Forlenza
authors.affiliation: Cell Biology and Immunology Group, Wageningen Institute of Animal Sciences, Wageningen University, P.O. Box 338, Wageningen 6700 AH, The Netherlands.
authors.forename: Geert F
authors.initials: GF
authors.lastname: Wiegertjes
authors.affiliation: School of Life Sciences, Keele University, Keele, Staffordshire ST5 5BG, United Kingdom. Electronic address: d.hoole@keele.ac.uk.
authors.forename: David
authors.initials: D
authors.lastname: Hoole
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D002347:Carps / Q000235:genetics / Q000276:immunology; D004032:Diet / Q000662:veterinary; D019587:Dietary Supplements; D029941:Fish Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D005786:Gene Expression Regulation / Q000187:drug effects*; D007369:Interferon Inducers / Q000494:pharmacology; D008969:Molecular Sequence Data; D064547:Myxovirus Resistance Proteins / Q000235:genetics* / Q000378:metabolism; D011070:Poly I-C / Q000494:pharmacology*; D016415:Sequence Alignment / Q000662:veterinary; D051196:Toll-Like Receptor 3 / Q000235:genetics / Q000378:metabolism*; D047071:beta-Glucans / Q000276:immunology*
chemical_list: D029941:Fish Proteins; D007369:Interferon Inducers; D064547:Myxovirus Resistance Proteins; D051196:Toll-Like Receptor 3; D047071:beta-Glucans; D011070:Poly I-C
keywords: Antiviral; Cyprinus carpio; TLR3; Type-I IFN response; β-Glucan