Submitted to: Immunogenetics
Publication Type: Peer reviewed journal
Publication Acceptance Date: 1/1/2006
Publication Date: 5/1/2006
Citation: Wiens, G.D., Glenney, G.W., Lapatra, S.E., Welch, T.J. 2006. Identification of novel rainbow trout (Onchorynchus mykiss) chemokines, cxcd1 and cxcd2: Mrna expression following Yersinia ruckeri vaccination and challenge. Immunogenetics. 2006 May;58(4):308-23. Epub 2006 Mar 29. Interpretive Summary: A better understanding of the immune system is required to improve health and disease resistance of fish. A first step toward this goal is the identification and characterization of genes and factors that regulate the immune response to pathogens. In mice and humans, chemokines play important roles in recruiting immune cells to sites of infection. In mammals, sixteen CXC chemokine genes have been identified while only a few CXC chemokine genes have been identified in fish. In this manuscript, we describe two new rainbow trout chemokine genes: CXCd1 and CXCd2. These genes were expressed in most tissues of healthy rainbow trout. Levels of gene expression increased in the major immune organs (spleen and anterior kidney) following either vaccination with dead bacteria or infection with the live Yersinia ruckeri bacteria. Infection of trout with another pathogen, the infectious hematopoietic necrosis virus, did not increase levels of gene expression indicating that the CXCd genes are not up-regulated in response to all pathogens. Our data suggest that measurement of CXCd1 and CXCd2 gene expression may be of future interest as biomarkers for an ongoing immune response to Yersinia ruckeri and as targets for selection of disease resistant fish.
Technical Abstract: Chemokines play important roles in controlling leukocyte trafficking under normal and inflammatory conditions. Sixteen CXC chemokines have been identified in the human and mouse genomes, while considerably fewer teleost fish CXC chemokines have been reported. Here, we describe a novel clade of trout (Onchorynchus mykiss) CXC chemokines, designated Onmy CXCd, and we identify a novel gene, CXCd1, and a putative duplicate, CXCd2. The trout CXCd proteins contain 112 amino acids and the CXCd1 gene is comprised of four exons and three introns. Constitutive CXCd mRNA expression was detected in skin, gill, visceral fat, and posterior kidney tissues, while low transcript levels were present in the anterior kidney and spleen. Spleen CXCd transcript abundance increased 1 day after bath vaccination (fourfold) and subsided to basal levels by 7 days postvaccination. Challenge with viable Yersinia ruckeri induced expression of trout CXCd RNA up to ninefold in the spleen. The number of viable Y. ruckeri were significantly correlated with CXCd gene transcript abundance (P = 0.0051, Spearman correlation 0.497, n = 30 fish), and fish with the highest bacterial loads had the highest CXCd expression. In contrast, pro-inflammatory cytokine IL-1-beta2 mRNA levels were elevated in fish infected with low numbers of Y. ruckeri, while diminishing in heavily infected fish. CXCd mRNA expression was not increased in rainbow trout infected with infectious hematopoietic necrosis virus, suggesting that up-regulation may be pathogen-specific. Taken together, these results indicate that CXCd transcript elevation follows the pro-inflammatory cytokine response to Y. ruckeri and may be a relevant immunological marker of exposure.