title: Response of toll-like receptors, lysozyme, and IGF-I in back-cross hybrid (F1 male (blue x channel) x female channel) catfish challenged with virulent Edwardsiella ictaluri.
abstract: Responses of toll-like receptors (TLR3 and TLR5), lysozyme, and insulin-like growth factor-I (IGF-I) to experimental challenge with virulent Edwardsiella ictaluri were measured in back-cross hybrid (F1 male (blue x channel) x female channel) catfish. The resistance levels to E. ictaluri and host response mechanisms of back-cross hybrids are unknown. Fish were challenged with virulent E. ictaluri and sampled pre-challenge, 2 h and 2, 5, 8, 14, and 21 days post-challenge. Levels of mRNA expression of two toll-like receptors (TLR3 and TLR5) in liver, kidney, spleen, and stomach, plasma lysozyme activity, and circulating IGF-I levels were measured at each timepoint. Throughout challenge, TLR3 was expressed at higher levels than TLR5 in liver (P=0.0011) and kidney (P=0.0007) whereas TLR5 was more highly expressed than TLR3 in stomach (P=0.0032). TLR3 was upregulated in comparison to non-exposed controls in liver (P=0.0015) and stomach (P<0.0001) on day 14 and TLR5 was upregulated in liver (P=0.0175) on days 2 through 8. Plasma lysozyme activity peaked on day 5 (P<0.001) and IGF-I levels significantly decreased on days 2 through 14 (P<0.0001). TLR expression patterns suggest that both TLR3 and TLR5 may play a role in host response to bacterial challenge. Plasma lysozyme activity also increased and circulating IGF-I decreased in response to the presence of the pathogen.
authors.affiliation: USDA-ARS Catfish Genetics Research Unit, Thad Cochran National Warmwater Aquaculture Center, Stoneville, MS 38776, USA. abilodeau@ars.usda.gov
authors.forename: A Lelania
authors.initials: AL
authors.lastname: Bilodeau
authors.forename: Brian C
authors.initials: BC
authors.lastname: Peterson
authors.forename: Brian G
authors.initials: BG
authors.lastname: Bosworth
mesh_terms: D000818:Animals; D002397:Catfishes; D020610:Edwardsiella ictaluri; D004756:Enterobacteriaceae Infections / Q000378:metabolism / Q000662:veterinary*; D005393:Fish Diseases / Q000378:metabolism*; D020869:Gene Expression Profiling / Q000662:veterinary; D006824:Hybridization, Genetic; D007334:Insulin-Like Growth Factor I / Q000378:metabolism*; D009113:Muramidase / Q000378:metabolism*; D012333:RNA, Messenger / Q000378:metabolism*; D013997:Time Factors; D051193:Toll-Like Receptors / Q000378:metabolism*
chemical_list: D012333:RNA, Messenger; D051193:Toll-Like Receptors; D007334:Insulin-Like Growth Factor I; D009113:Muramidase