Molecular cloning and mRNA expression analysis of interleukin-8 gene in Japanese sea perch (Lateolabrax japonicus)

Immune response of Rhinogobio ventralis to Ichthyophthirius multifiliis infection: Insights from histopathological and real-time gene expression analyses

Ichthyophthirius multifiliis is a parasite that poses a considerable threat to aquaculture and the ornamental fish industry, but with limited effective treatment options available. This study employed RT-qPCR to detect and analyze the expression changes of partial toll-like receptor (TLR) genes (TLR1 and TLR21), adapter protein and signal transduction molecule genes (MyD88, TRIF, NF-κB, IRAK4, and IRF3), and cytokines (IL-6, IL-8, IL-13, CXC-α and CXCR1), as well as complement C3, in the skin, gill, fin, liver, head kidney and spleen of Rhinogobio ventralis under different infection conditions. Additionally, tissue sections and scanning electron microscopy were utilized to observe the pathological changes in the gills and fins of R. ventralis after infection with I. multifiliis. The expression patterns of TLR-related DEGs (differentially expressed genes) in diseased wild fish were analyzed, revealing upregulation of TLR1, TLR21, MyD88, NF-κB, IRAK4, TRIF, IRF3, IL-6, IL-8, IL-13, CXC-α, CXCR1, and C3 genes in various tissues, indicating that these genes may be involved in the immune response of R. ventralis to I. multifiliis infection. To further analyze the gene expression of sampled from the field, an artificial infection model of R. ventralis was established under laboratory conditions, with additional sampling from the skin and fins. These genes continued to show varying degrees of upregulation, but the results were not entirely consistent with those from Wudongde samples, which may be due to the more complex environment in the wild or differences in the degree of I. multifiliis infection in wild fish. The infection of I. multifiliis caused severe damage to the gills and fins of R. ventralis, characterized by extensive secretions on the gill and fin surfaces, with the presence of attached I. multifiliis trophonts, including damage and loss of gill filaments, swollen gill lamellae, and deformed gill plates, as well as cell proliferation and necrosis of gill epithelial cells. This study sheds light on the role of the TLR signaling pathway in resisting I. multifiliis infection and its associated histopathological changes in R. ventralis, providing valuable insights for the prevention and treatment of I. multifiliis infection in R. ventralis.

Identification, Expression and Antimicrobial Functional Analysis of Interleukin-8 (IL-8) in Response to Streptococcus iniae and Flavobacterium covae in Asian Seabass (Lates calcarifer Bloch, 1790)

In this research, the proinflammatory cytokine interleukin-8 (IL-8) was shown to play a key role in inflammatory responses in fish. This study involved the cloning of the gene that encodes IL-8 in Asian seabass (Lates calcarifer) as well as analyses of its expression and function in this fish. The expression levels of LcIL-8 indicated that it was broadly expressed in most analyzed tissues, with the most predominant expression in the whole blood 6 to 24 h after infection with S. iniae at concentrations of 105 colony-forming units (CFU)/fish (p < 0.05). After fish were immersed in F. covae, the LcIL-8 transcript was upregulated in the gills, liver and intestine, and the highest expression level was observed in the gills. However, LcIL-8 was downregulated in all the tested tissues at 48 and 96 h after infection with the two pathogenic strains, indicating that Lc-IL8 has a short half-life during the early immune responses to pathogens. Moreover, the MIC of the rLcIL-8 protein against S. iniae was 10.42 ± 3.61 µg/mL. Furthermore, functional analyses clearly demonstrated that 10 and 100 µg of the rLcIL-8 protein efficiently enhanced the phagocytic activity of Asian seabass phagocytes in vitro (p < 0.05). Additionally, in vivo injection of S. iniae following the rLcIL-8 protein indicated that 50 and 100 µg of rLc-IL-8 were highly effective in protecting fish from this pathogen (p < 0.001). The obtained results demonstrate that rLcIL-8 possesses a biological function in the defense against bacterial infections in Asian seabass.

Molecular characterization and gene expression analysis of the pro-inflammatory cytokines IL-1β and IL-8 in the South American fish Piaractus mesopotamicus challenged with Aeromonas dhakensis

In the present study, the complete characterization of cDNA and genomic sequences of IL-1β and IL-8, as well as the expression profile of these genes in the South American fish pacu (Piaractus mesopotamicus) is provided. The full-length pmIL-1β cDNA was composed of 1208 nucleotides that would produce a precursor peptide with 273 amino acid residues. A putative caspase-1 cleavage site, similar to what is found in mammalian IL-1β, was identified producing a mature peptide with a theoretical molecular weight of 17.21 kDa. The pmIL-8 cDNA sequence consisted of 1019 nucleotides which encoded a 95-amino acid protein with a theoretical molecular weight of 10.43 kDa that showed all typical CXC chemokine features, including a 20-residue signal peptide and four conserved cysteine residues. Constitutive mRNA expression was detected for both genes in the liver, head kidney, gill, intestine, skin and spleen. After a bacterial challenge, up-regulation was detected for both pmIL-1β and pmIL-8 in the spleen and head kidney at 12 h post-infection. At 24 h post-infection there was a decrease in the expression of both genes, with pmIL-8 showing a significant down-regulation in the liver and head kidney when compared to the control groups.

Comparative Characterization of Two cxcl8 Homologs in Oplegnathus fasciatus: Genomic, Transcriptional and Functional Analyses

CXCL8 (interleukin-8, IL-8) is a CXC family chemokine that recruits specific target cells and mediates inflammation and wound healing. This study reports the identification and characterization of two cxcl8 homologs from rock bream, Oplegnathus fasciatus. Investigation of molecular signature, homology, phylogeny, and gene structure suggested that they belonged to lineages 1 (L1) and 3 (L3), and designated Ofcxcl8-L1 and Ofcxcl8-L3. While Ofcxcl8-L1 and Ofcxcl8-L3 revealed quadripartite and tripartite organization, in place of the mammalian ELR (Glu-Leu-Arg) motif, their peptides harbored EMH (Glu-Met-His) and NSH (Asn-Ser-His) motifs, respectively. Transcripts of Ofcxcl8s were constitutively detected by Quantitative Real-Time PCR (qPCR) in 11 tissues examined, however, at different levels. Ofcxcl8-L1 transcript robustly responded to treatments with stimulants, such as flagellin, concanavalin A, lipopolysaccharide, and poly(I:C), and pathogens, including Edwardsiella tarda, Streptococcus iniae, and rock bream iridovirus, when compared with Ofcxcl8-L3 mRNA. The differences in the putative promoter features may partly explain the differential transcriptional modulation of Ofcxcl8s. Purified recombinant OfCXCL8 (rOfCXCL8) proteins were used in in vitro chemotaxis and proliferation assays. Despite the lack of ELR motif, both rOfCXCL8s exhibited leukocyte chemotactic and proliferative functions, where the potency of rOfCXCL8-L1 was robust and significant compared to that of rOfCXCL8-L3. The results, taken together, are indicative of the crucial importance of Ofcxcl8s in inflammatory responses and immunoregulatory roles in rock bream immunity.

Molecular cloning, biological effect, and tissue distribution of interleukin-8 protein in mandarin fish (Siniperca chuasti) upon Flavobacterium columnare infection

Interleukin-8 (IL-8), a CXC-type chemokine, plays a key role in acute inflammation by recruiting neutrophils in mammals. In the present study, the open reading frame (ORF) of IL-8, encoding 99 amino acids was cloned in mandarin fish, and its function in inflammation was investigated. The IL-8 contains four conserved cysteine residues, with the first two forming the CXC signature motif. The genomic sequence of mandarin fish IL-8 has four exons and three introns, a typical gene organization of the CXC chemokine. Bioactive recombinant IL-8 (rIL-8) exhibited a chemotactic effect on head kidney leukocytes in vitro, and activates the transcription of the inflammatory genes, IL-8 and IL-1β. When mandarin fish was challenged intraperitoneally with the pathogenic bacterium Flavobacterium columnare G₄, the steady-state protein level of IL-8 was up-regulated in trunk kidney and head kidney. These results suggest that IL-8 is a functional CXC chemokine in mandarin fish, and plays a key role in the inflammatory responses towards bacterial infection.

Molecular Characterization of Pro-Inflammatory Cytokines Interleukin-1β and Interleukin-8 in Asian Elephant (Elephas maximus)

Interleukin (IL)-1β and IL-8 are pro-inflammatory cytokines produced primarily by monocytes and macrophages in response to a variety of microbial and nonmicrobial agents. As yet, no molecular data have been reported for IL-1β and IL-8 of the Asian elephant. In the present study, we have cloned and sequenced the cDNA encoding IL-1β and IL-8 of the Asian elephant. The open reading frame (ORF) of Asian elephant IL-1β is 789 bp in length, encoded a propeptide of 263 amino acid polypeptide. The predicted protein revealed the presence of IL-1 family signature motif and an ICE cut site. Whereas, IL-8 contained 321 bp of open reading frame. Interestingly, the predicted protein sequence of 106 aa, contains an ELR motif immediately upstream of the CQC residues, common in all vertebrate IL-8 molecules. Identity levels of the nucleic acid and deduced amino acid sequences of Asian elephant IL-1β ranged from 68.48 (Squirrel monkey) to 98.57% (African elephant), and 57.78 (Sheep) to 98.47% (African elephant), respectively, whereas that of IL-8 ranged from 72.9% (Human) to 87.8% (African elephant), and 63.2 (human, gorilla, chimpanzee) to 74.5% (African elephant, buffalo), respectively. The phylogenetic analysis based on deduced amino acid sequenced showed that the Asian elephant IL-1β and IL-8 were most closely related to African elephant. Molecular characterization of these two cytokines, IL-1β and IL-8, in Asian elephant provides fundamental information necessary to progress the study of functional immune responses in this animal and gives the potential to use them to manipulate the immune response as recombinant proteins.

Molecular characterization and comparative expression analysis of two teleostean pro-inflammatory cytokines, IL-1β and IL-8, from Sebastes schlegeli

Interleukin 1β (IL-1β) and interleukin 8 (IL-8) are two major pro-inflammatory cytokines which play a central role in initiation of inflammatory responses against bacterial- and viral-infections. IL-1β is a member of the interleukin 1 family proteins and IL-8 is classified as a CXC-chemokine. In the current study, putative IL-1β and IL-8 counterparts were identified from a black rockfish transcriptomic database and designated as RfIL-1β and RfIL-8. The RfIL-1β cDNA sequence consists of 1140 nucleotides with a 759bp open reading frame (ORF) which encodes a 252 amino acid (aa) protein, whereas the RfIL-8 cDNA sequence (898bp) harbors a 300bp ORF encoding a 99 aa protein. Furthermore, the RfIL-1β aa sequence contains an IL-1 super family-like domain and an N-terminal IL-1 super family propeptide, while the amino acid sequence of RfIL-8 consists of a typical chemokine-CXC domain. Analysis of sequenced BAC clones containing RfIL-1β and RfIL-8 showed each gene to contain 4 exons interrupted by 3 introns. Pairwise comparison and phylogeny analysis of these cytokine sequences clearly revealed their closer relationship with other corresponding members of teleosts compared to birds and mammals. Constitutive differences in RfIL-1β and RfIL-8 mRNA expression were detected in a tissue-specific manner with the highest expression of each mRNA in spleen tissue. Two immune challenge experiments were conducted with Streptococcus iniae and polyinosinic:polycytidylic acid (poly I:C; a viral double stranded RNA mimic), and transcripts were quantified in spleen and peripheral blood cells. Significantly increased RfIL-1β and RfIL8 transcript levels were detected with almost similar profile patterns, further suggesting a putative involvement of these pro-inflammatory cytokines in the rockfish immunity.

Molecular characterization of a CXCL8-like protein from ayu and its effect on chemotaxis of neutrophils and monocytes/macrophages

CXCL8, a CXC-type chemokine, plays a crucial role in acute inflammation by recruiting and mediating neutrophils and other cells. In this study, the cDNA and genomic DNA sequence of a CXCL8-like protein (PaCXCL8l) from ayu (Plecoglossus altivelis) was determined. Sequence analysis showed that PaCXCL8l represented the typical structure of animal CXCL8s. Phylogenetic tree analysis indicated that PaCXCL8l was closest to CXCL8 of Atlantic cod (Gadus morhua). Constitutive expression of PaCXCL8l was detected in all tested tissues and monocytes/macrophages, and its expression dramatically increased upon Listonella anguillarum infection. In vitro, recombinant PaCXCL8l exhibited a significant chemotactic effect on neutrophils at 0.1 μg/ml and on monocytes/macrophages at 1.0 μg/ml. In vivo, the numbers of peritoneal neutrophils and monocytes/macrophages were both up-regulated following intraperitoneal administration of recombinant PaCXCL8l. These results suggest that PaCXCL8l is crucially involved in the immune response of ayu by mediating chemotaxis of neutrophils and monocytes/macrophages.

Molecular and expression characterizations of interleukin-8 gene in large yellow croaker (Larimichthys crocea)

IL-8 plays a crucial role in acute inflammation by recruiting and mediating neutrophils and other cells and in initiating the oxidative burst in neutrophils and inducing wound healing by promoting angiogenesis. In the present study, the full-length cDNA and genome sequence of interleukin-8 (LcIL-8) were cloned from large yellow croaker Larimichthys crocea. The LcIL-8 cDNA sequence was 931 bp, containing a 118-bp 5'-untranslated region (UTR), a 528-bp 3'-UTR and a 285-bp open reading frame (ORF) which encoded 94 amino acids. A putative signal peptide including 20 amino acid residues was found at N-terminal in LcIL-8 protein. And a small cytokine (SCY) domain showing a typical CXC chemokine gene organization was predicted in LcIL-8. The genome sequence of LcIL-8 gene was composed of 1930 nucleotides, including four exons and three introns. Quantitative real-time PCR analysis indicated a broad expression of LcIL-8 in most detected tissues, with the most predominant expression in liver. After injection with LPS, Vibrio parahaemolyticus and poly I:C, LcIL-8 expression levels showed up-regulation in head-kidney and spleen. The peak value was in the spleen with 6 times (at 6 h) greater expression than in the control after LPS injection (p < 0.05). However, LcIL-8 transcripts showed down-regulation in the liver after all the three stimulants injection. Recombinant LcIL-8 mature peptide was produced by Escherichia coli, which enhanced the production of superoxide anion in PCK cells. In addition, 5 single-nucleotide polymorphisms (SNPs) were identified in LcIL-8 gene. The results suggested that LcIL-8 might play an important role in fish's immune response, and the SNPs might be used as potential candidate molecular markers for selection for disease-resistant large yellow croaker.

Molecular cloning and expression analysis of a F-type lectin gene from Japanese sea perch (Lateolabrax japonicus)

The techniques of homology cloning and anchored PCR were used to clone the fucose-binding lectin (F-type lectin) gene from Japanese sea perch (Lateolabrax Japonicus). The full-length cDNA of sea perch F-lectin (JspFL) contained a 5' untranslated region (UTR) of 39 bp, an ORF of 933 bp encoding a polypeptide of 310 amino acids with an estimated molecular mass of 10.82 kDa and a 3' UTR of 332 bp. The searches for nucleotides and protein sequence similarities with BLAST analysis indicated that the deduced amino acid sequence of JspFL was homological to the Fucose-binding lectin in other fish species. In the JspFL deduced amino acid sequence, two tandem domains that exhibit the eel carbohydrate-recognition sequence motif were found. The temporal expressions of gene in the different tissues were measured by real-time PCR. And the mRNA expressions of the gene were constitutively expressed in tissues including spleen, head-kidney, liver, gill, and heart. The JspFL expression in spleen was different during the stimulated time point, 2 h later the expression level became up-regulated, and 6 h later the expression level became down-regulated. The result indicated that JspFL was constitutive and inducible expressed and could play a critical role in the host-pathogen interaction.

Understanding the vertebrate immune system: insights from the reptilian perspective

Reptiles are ectothermic amniotes, providing the key link between ectothermic anamniotic fishes and amphibians, and endothermic amniotic birds and mammals. A greater understanding of reptilian immunity will provide important insights into the evolutionary history of vertebrate immunity as well as the growing field of eco-immunology. Like mammals, reptile immunity is complex and involves innate, cell-mediated and humoral compartments but, overall, there is considerably less known about immune function in reptiles. We review the current literature on each branch of the reptilian immune system, placing this information in context to other vertebrates. Further, we identify key areas that are prime for research as well as areas that are lagging because of lack of reagents in non-model systems.