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Mammalian serum amyloid P component (SAP) recognizes a wide range of exogenous pathogenic substances and activates a complementary pathway leading to pathogen clearance. To determine the potential roles of SAP in the fish immune system, SAP (RbSAP2) gene was cloned from ESTs analysis of rock bream ( Oplegnathus fasciatus ), which consisted of a signal peptide and pentraxin domain. Phylogenetic analysis revealed that the RbSAP2 gene was classified with other known fish SAPs. RbSAP2 was highly expressed in the liver of healthy rock bream. Overall, pathogen exposure led to an induction of RbSAP2 in the liver and spleen, although this effect was not observed in the spleen following infection with Edwardsiella tarda . A high concentration of recombinant RbSAP2 (rRbSAP2) showed lower growth Streptococcus iniae than control in the absence of Ca 2+ , whereas E. tarda growth was decreased by high concentration of rRbSAP in the presence of the Ca 2+ . These results suggest that RbSAP plays an important role in the immune response against invading pathogens. [ABSTRACT FROM AUTHOR]

Abstract: Lipopolysaccharide (LPS)-induced tumor necrosis factor (TNF)-α factor (LITAF) plays an important role controlling the expression of TNF-α and the other cytokine genes in the presence of LPS. However, two LITAF homologues have not been characterized in fish. In this study, we cloned two distinct LITAF (RbLITAF1 and RbLITAF2) cDNAs from rock bream (Oplegnathus fasciatus) and characterized their expression profiles after infection with Edwardsiella tarda, Streptococcus iniae or red seabream iridovirus (RSIV). The coding regions of RbLITAF1 and RbLITAF2 cDNAs were 492 bp and 417 bp, encoding 153 and 138 amino acid residues, respectively. The genes consisted of a LITAF domain. RbLITAF1 was highly expressed in the spleen and heart of healthy rock bream, whereas RbLITAF2 was highly expressed in the gill, intestine and stomach. In spleen, the gene expression of RbLITAF1 and RbLITAF2 were increased until 5 days post-infection (dpi), and then decreased at 7 dpi. In kidney, E. tarda and RSIV infection led to induction of the RbLITAF1 gene at 1 dpi, RbLITAF2 gene was down-regulated after pathogen infection. These results suggest that RbLITAFs may be involved in the LITAF-mediated immune response and regulate systemic immune responses against pathogen infection. [Copyright &y& Elsevier]

Abstract: CD200 plays an important role in delivering an immunoregulatory signal to the immune system through interaction with its receptor. However, CD200 has not been characterized and its function in teleosts is unknown. In this study, the rock bream (Oplegnathus fasciatus) CD200 gene (RbCD200) was cloned and its expression profile was analyzed after infection with Edwardsiella tarda, Streptococcus iniae or red seabream iridovirus (RSIV). The coding region of RbCD200 cDNA was 855 bp, encoding 284 amino acid residues. The gene consisted of two extracellular Ig-like domains and a transmembrane domain. RbCD200 was highly expressed in the brain, erythrocytes, intestine and stomach of healthy rock bream. In the spleen, RbCD200 gene expression was down-regulated until 48 h after E. tarda exposure, except at 12 h RbCD200 gene expression was down-regulated then up-regulated at 12 h and 24 h after infection with S. iniae and RSIV, respectively. In the whole kidney, the RbCD200 gene was down-regulated in response to infection with E. tarda and S. iniae. However, RSIV infection increased RbCD200 gene expression in whole kidney until 48 h. These results suggest that RbCD200 is differentially expressed in the spleen and whole kidney after infection with different pathogens. [Copyright &y& Elsevier]

Abstract: Toll-like receptors (TLRs) are essential for activation of the innate immune system in response to invading pathogens. TLR14, which is unique to fish, has been identified in several fish species, but its function is unclear. In this study, Japanese flounder (Paralichthys olivaceus) TLR14 gene (JfTLR14) was cloned and its expression profiles were analyzed after infection with viral hemorrhagic septicemia virus, gram-positive Streptococcus iniae and gram-negative Edwardsiella tarda. The coding region of JfTLR14 cDNA was 2,607 bp, encoding 878 amino acid residues. JfTLR14 was highly expressed in head kidney of healthy flounder. In response to infection with VHSV and S. iniae, the JfTLR14 gene was up-regulated at only 1 day post-infection (dpi). However, E. tarda infection increased JfTLR14 gene expression from 1 to 6 dpi. These results imply that JfTLR14 participates more in the immune response against E. tarda infection than in the immune responses to other pathogen infections. [ABSTRACT FROM AUTHOR]

Abstract: Mammalian interleukin (IL)-15 plays an important role in the activation of CD8+ T cells and natural killer (NK) cells along with its receptor α (IL-15Rα). To understand the potential roles of IL-15 and IL-15Rα in fish, we identified IL-15 and IL-15Rα cDNA from rock bream (Oplegnathus fasciatus) and investigated their gene expression profiles after bacterial and viral infection. Coding regions of rock bream (Rb) IL-15 and RbIL-15Rα cDNAs were 534 and 402 bp encoding 177 and 133 amino acid residues, respectively. The sushi domain of IL-15Rα was highly conserved between rock bream and other species. Unlike other IL-15Rαs, RbIL-15Rα does not have a transmembrane region. Gene expression of RbIL-15 and RbIL-15Rα was widely expressed in different tissues of healthy fish, especially immune-related tissues. RbIL-15 and RbIL-15Rα were highly induced in the kidney and spleen after infection with Edwardsiella tarda, Streptococcus iniae and red seabream iridovirus. Gene expression patterns of RbIL-15 and RbIL-15Rα were similar in the kidney and spleen after pathogen infection. However, these genes were differentially induced in the liver after pathogen infection. These results suggest that the different responses of RbIL-15 and RbIL-15Rα to pathogen infection may be induced by different tissues or cell types. [Copyright &y& Elsevier]

Abstract: Cathepsins are lysosomal cysteine proteases belonging to the papain family, whose members play important roles in normal metabolism for the maintenance of cellular homeostasis. Rock bream (Oplegnathus fasciatus) cathepsin H (RbCTSH) cDNAs were identified by expressed sequence tag analysis of a lipopolysaccharide-stimulated rock bream liver cDNA library. The full-length RbCTSH cDNA (1326 bp) contained an open reading frame of 978 bp encoding 325 amino acids. The presence of an ERFNIN-like motif was predicted in the propeptide region of RbCTSH. Furthermore, multiple alignments showed that the EPQNCSAT region was well conserved among other cathepsin H sequences. Phylogenetic analysis revealed that RbCTSH is most closely related to Nile tilapia cathepsin H. RbCTSH was expressed significantly in the intestine, spleen, head kidney and stomach. RbCTSH mRNA expression was also examined in several tissues under conditions of bacterial and viral challenge. All examined tissues of fish infected with Edwardsiella tarda, Streptococcus iniae and red sea bream iridovirus (RSIV) showed significant increases in RbCTSH expression compared to the control. In the kidney and spleen, RbCTSH mRNA expression was upregulated markedly following infection with bacterial pathogens. These findings indicate that RbCTSH plays an important role in the innate immune response of rock bream. Furthermore, these results provide important information for the identification of other cathepsin H genes in various fish species. [Copyright &y& Elsevier]