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United States Department of Agriculture

Agricultural Research Service

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

Authors
item Bourgeois, Lanie
item Peterson, Brian
item Bosworth, Brian

Submitted to: Fish and Shellfish Immunology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: March 3, 2006
Publication Date: July 11, 2006
Citation: Bilodeau, A.L., Peterson, B.C., Bosworth, B.G. 2006. 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. Fish and Shellfish Immunology 20:29-39.

Interpretive Summary: The resistance levels to E.ictaluri and host response mechanisms of back-cross hybrids are unknown. To address this, 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. Patterns of mRNA expression of the two toll-like receptors suggest that TLR3 and 5 both play a role in host response to bacterial challenge. Plasma lysozyme activity also increased in response to the presence of the pathogen. Reduction and then recovery of IGF-I may be related to reduction in feed intake concominant with acute infection.

Technical 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, 2, 5, 8, 14, and 21 d 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 TLR3 and 5 both 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.

Last Modified: 10/23/2014
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