The cytokine IL-1β from the crocodile icefish Chionodraco hamatus (Perciformes: Channichthyidae)

Temperature modulates the immunological response of the sub-antarctic notothenioid fish Eleginops maclovinus injected with Piscirickettsia salmonis

Eleginops maclovinus is a eurythermic fish that under natural conditions lives in environments with temperatures ranging from 4 to 18 °C and can be usually captured near salmon farming areas. The aim of this study was to evaluate the effect of temperature over the innate and adaptive immune response of E. maclovinus challenged with Piscirickettsia salmonis following different treatments: C (control injection with culture medium at 12 °C), C+ (bacterial injection at 12 °C), 18 °C c/A + B (injection with culture medium in acclimation at 18 °C), 18 °C c/A + B (bacterial injection in acclimation at 18 °C), 18 °C s/A + M (injection with culture medium without acclimation at 18 °C) and 18 °C s/A + B (bacterial injection without acclimation at 18 °C). Each injection had 100 μL of culture medium or with 100 μL at a concentration 1 × 10⁸ of live bacteria, sampling six fish per group at 4, 8, 12, 16 and 20 days post-injection (dpi). Expression of the mRNA related with the innate immune response gene (TLR1, TLR5, TLR8, NLRC3, NLRC5, MyD88 and IL-1β) as well as the adaptive immune response gene (MHCI, MHCII, IgMs and IgD) were measured in spleen and head kidney. Gene expression profiles were treatment-type and time dependent. Levels of Immunoglobulin M (IgM) increased in challenged groups with P. salmonis from day 8-20 post challenge, which suggest activation of B cells IgM + through P. salmonis epitope detection. Additionally, a rise in temperature from 12 °C (C+) to 18 °C (with/without acclimation) also resulted in antibody increment detected in serum with significant differences between "18 °C c/A + B" and "18 °C s/A + B" groups. This is the first study that evaluates the effect of temperature changes and mRNA expression related with immune system gene over time on E. maclovinus, a native wild life fish that cohabits in the salmon farming environment.

Immunological response of the Sub-Antarctic Notothenioid fish Eleginops maclovinus injected with two strains of Piscirickettsia salmonis

Eleginops maclovinus is an endemic fish to Chile that lives in proximity to salmonid culture centers, feeding off of uneaten pellet and salmonid feces. Occurring in the natural environment, this interaction between native and farmed fish could result in the horizontal transmission of pathogens affecting the aquaculture industry. The aim of this study was to evaluate the innate and adaptive immune responses of E. maclovinus challenged with P. salmonis. Treatment injections (in duplicate) were as follows: control (100 μL of culture medium), wild type LF-89 strain (100 μL, 1 × 10⁸ live bacteria), and antibiotic resistant strain Austral-005 (100 μL, 1 × 10⁸ live bacteria). The fish were sampled at various time-points during the 35-day experimental period. The gene expression of TLRs (1, 5, and 8), NLRCs (3 and 5), C3, IL-1β, MHCII, and IgMs were significantly modulated during the experimental period in both the spleen and gut (excepting TLR1 and TLR8 spleen expressions), with tissue-specific expression profiles and punctual differences between the injected strains. Anti-P. salmonis antibodies increased in E. maclovinus serum from day 14-28 for the LF-89 strain and from day 14-35 for the Austral-005 strain. These results suggest temporal activation of the innate and adaptive immune responses in E. maclovinus tissues when injected by distinct P. salmonis strains. The Austral-005 strain did not always cause the greatest increases/decreases in the number of transcripts, so the magnitude of the observed immune response (mRNA) may not be related to antibiotic resistance. This is the first immunological study to relate a pathogen widely studied in salmonids with a native fish.

The complete mitochondrial genome of Chionodraco hamatus (Notothenioidei: Channichthyidae) with phylogenetic consideration

The complete mitochondrial genome of Chionodraco hamatus was obtained, which was 17 457 bp in length. This genome consists of 13 protein-coding genes, 22 transfer RNA genes, 2 ribosomal RNA genes and a putative control region. Of the 37 genes, 28 were encoded by heavy strand, while 9 were encoded by light strand. Overall base composition of mitogenome is estimated to be 26.38% for A, 17.44% for G, 26.00% for T, 30.18% for C, respectively, with a slight A + T bias (52.38%). The phylogenetic analysis based on 13 concatenated protein-coding genes suggested that C. hamatus as a sister species to Chionodraco myersi was clustered in family Chionodraco. The complete mitochondrial genome sequence of C. hamatus could provide a basic data for the studies on evolution for low temperature adaptability, population structure, molecular systematic, stock evaluation and conservation genetics.

Molecular characterization of an IL-1β gene from ayu, Plecoglossus altivelis

IL-1β plays a crucial role as a prototypical proinflammatory cytokine in immune responses and has been shown to affect macrophage functions. However, the effects of putative IL-1β homologs on fish macrophages are still less known. Here, we cloned the full-length cDNA sequence of IL-1β (aIL-1β) gene from ayu, Plecoglossus altivelis. Phylogenetic analysis indicated that aIL-1β was closest to that of Atlantic salmon (Salmo salar). Real-time quantitative PCR (RT-qPCR) revealed that aIL-1β transcript was mainly expressed in spleen, head kidney and gill, and dramatically increased in various tissues after Listonella anguillarum infection. Subsequently, aIL-1β was prokaryotic expressed and purified to prepare anti-aIL-1β antibody. After L. anguillarum challenge, the aIL-1β mRNA and protein levels were significantly up-regulated in ayu monocytes/macrophages. Moreover, aIL-1β neutralization did not change phagocytic capability, but reduced bacterial killing capability in ayu head kidney-derived monocytes/macrophages. Therefore, aIL-1β may play an important role in immune response of ayu, especially, contributing to bacterial killing of monocytes/macrophages.

Molecular cloning and characterization of interleukin-1β in half-smooth tongue sole Cynoglossus semilaevis

As a member of the interleukin (IL)-1 family, IL-1β is a prototypical proinflammatory cytokine, which plays a crucial role in immune responses. Herein, we reported the full length cDNA of IL-1β in half-smooth tongue sole (Cynoglossus semilaevis). The csIL-1β cDNA contained a 130 bp 5' UTR, a 417 bp 3' UTR and a 741 bp coding sequence (CDS) that translated into a polypeptide of 246 amino acids. The protein sequence included a typical IL-1 family signature and lacked an interleukin-converting enzyme (ICE) cut site. RT-PCR analysis indicated a broad expression of csIL-1β, especially in immune-related organs. After injection with inactive Vibrio anguillarum, the expression of csIL-1β was induced in the head kidney and spleen and reached the highest level at 8 h post injection. Higher expression of csIL-1β was observed at gastrula stage, eye-bud stage and hatching stage and lower level of csIL-1β mRNA was detected at metamorphic stage. The expression of csIL-1β during development suggested IL-1β might be involved not only in immunity but also development. Taken together, the present study indicated that csIL-1β played an important role in immune responses and development like its mammalian counterparts, although species-specific features were present.

LPS induces gene expression of interleukin-1beta in conger eel (Conger myriaster) macrophages: first cytokine sequence within Anguilliformes

Our aim was to comprehensively analyze the immune response in Anguilliformes macrophages and to survey cytokine genes expressed from them. We therefore used suppression subtractive hybridization (SSH) to randomly clone molecules that are specifically expressed in conger eel (Conger myriaster) macrophages when cells are stimulated by LPS. As a result, we succeeded in identifying a conger eel IL-1beta. This is the first report on cytokines in Anguilliformes, which is the most ancient order in living teleosts.