Isolation and characterization of chicken interleukin-17 cDNA

The avian immune genome – a glass half-full or half-empty?

Although in broad terms the avian immune response is remarkably similar to that of mammals, when one looks at specifics birds have a different repertoire of immune organs, cells and molecules compared to those characterized in mammals. Birds lack organized lymph nodes, yet have the Bursa of Fabricius. Birds lack neutrophils and functional eosinophils, yet have a distinct group of polymorphonuclear granulocytes known as heterophils. Birds also have a different repertoire of cytokines, chemokines, Toll-like receptors, defensins and integrins, as detailed in this review.

Changes in immune-related gene expression and intestinal lymphocyte subpopulations following Eimeria maxima infection of chickens

Coccidiosis, a major intestinal parasitic disease of poultry, induces a cell-mediated immune response against the etiologic agent of the disease, Eimeria. In the current study, the expression levels of gene transcripts encoding pro-inflammatory, Th1, and Th2 cytokines, as well as chemokines were measured in intestinal intraepithelial lymphocytes (IELs) after Eimeria maxima infection. In addition, changes in IEL numbers were quantified following E. maxima infection. Transcripts of the pro-inflammatory and Th1 cytokines IFN-gamma, IL-1beta, IL-6, IL-12, IL-15, IL-17, and IL-18 were increased 66- to 8 x 10(7)-fold following primary parasite infection. Similarly, mRNA levels of the Th2 cytokines IL-3, IL-10, IL-13, and GM-CSF were up-regulated 34- to 8800-fold, and the chemokines IL-8, lymphotactin, MIF, and K203 were increased 42- to 1756-fold. In contrast, IFN-alpha, TGF-beta4, and K60 transcripts showed no increased expression, and only the level of the Th2 cytokine IL-13 was increased following secondary E. maxima infection. Increases in intestinal T cell subpopulations following E. maxima infection also were detected. CD3(+), CD4(+), and CD8(+) cells were significantly increased at days 8, 6, and 7 post-primary infection, respectively, but only CD4(+) cells remained elevated following secondary infection. TCR1(+) cells exhibited a biphasic pattern following primary infection, whereas TCR2(+) cells displayed a single peak in levels. Taken together, these data indicate a global chicken intestinal immune response is produced following experimental Eimeria infection involving multiple cytokines, chemokines, and T cell subsets.

Analysis of chicken cytokine and chemokine gene expression following Eimeria acervulina and Eimeria tenella infections

The expression levels of mRNA encoding a panel of 28 chicken cytokines and chemokines were quantified in intestinal lymphocytes following Eimeria acervulina and Eimeria tenella primary and secondary infections. Compared with uninfected controls, transcripts of the pro-inflammatory cytokines IFN-alpha, IL-1beta, IL-6, and IL-17 were increased up to 2020-fold following primary infection. By contrast, following secondary infection by either microorganism, pro-inflammatory mRNAs levels were relatively unchanged (< or = 20-fold). Transcripts encoding the Th1 and Th1 regulatory cytokines IFN-gamma, IL-2, IL-10, IL-12, IL-15, IL-16, and IL-18 were uniformly increased 14-2471-fold after E. acervulina primary infection, but either unchanged (IL-15, IL-16, IL-18), increased (IFN-gamma, IL-10, IL-12), or decreased (IL-2) following E. tenella primary infection. Following secondary infections, Th1 cytokine mRNA levels were relatively unchanged, with the exception of IL-12 which was increased 1.5 x 10(5)-fold after E. acervulina and decreased 5.1 x 10(4)-fold after E. tenella infection. Transcripts for the Th2 or Th2 regulatory cytokines IL-3 and GM-CSF were increased up to 327-fold following primary or secondary infection with both parasites, while IL-4 and IL-13 mRNAs were decreased 25- to 2 x 10(5)-fold after primary or secondary infection. The dynamics of chicken chemokine expression revealed modest changes (<100-fold) following primary or secondary infection except for lymphotactin. When lymphocyte subpopulations were similarly analyzed, IFN-gamma, IL-2, IL-3, IL-15, and MIF were most highly increased in TCR2(+) cells following E. acervulina infection, while TCR1(+) cells only expressed high levels of IL-16 following E. tenella infection. In contrast, CD4(+) cells only expressed highest levels of IL-10 after E. acervulina infection, whereas these cells produced abundant transcripts for IFN-gamma, IL-3, IL-15, and MIF after E. tenella infection. We conclude that coccidiosis induces a diverse and robust primary cytokine/chemokine response, but a more subdued secondary response.

Identification, cloning and characterization of interleukin-17 and its family from zebrafish

Cytokines are one of the major signaling molecules involved in immunity. Many of these cytokines have been isolated in vertebrates and found to play a significant role in host defense mechanism. Interleukin-17 (IL-17) family of genes are known to have pro-inflammatory actions and associated with specific disease conditions, these genes are conserved across vertebrate evolution. In this study, computational screening for the zebrafish (Danio rerio) genome resulted in identification of five contigs harboring IL-17 genes. Zebrafish cDNA encoding five IL-17 genes exhibited percentage identities of 19.3%-61.9% with that of human homologs. The molecules show conservation of cysteines, important for disulphide bonds for IL-17 molecules. The structural composition of these genes shows two introns and three exons except for IL-17D gene that has only one intron and two exons. Phylogenetic analysis using maximum parsimony algorithm showed that zebrafish IL-17 genes clustered well with other IL-17 homologs further proving the structural similarity with IL-17 genes from other organisms. Expression analysis by RT-PCR revealed expression of IL-17 genes in normal and stimulated tissues of kidney, spleen, gills and intestine. The expression of IL-17 in un-stimulated tissues indicates that these genes may play important roles in normal conditions as well.

A genomic analysis of chicken cytokines and chemokines

As most mechanisms of adaptive immunity evolved during the divergence of vertebrates, the immune systems of extant vertebrates represent different successful variations on the themes initiated in their earliest common ancestors. The genes involved in elaborating these mechanisms have been subject to exceptional selective pressures in an arms race with highly adaptable pathogens, resulting in highly divergent sequences of orthologous genes and the gain and loss of members of gene families as different species find different solutions to the challenge of infection. Consequently, it has been difficult to transfer to the chicken detailed knowledge of the molecular mechanisms of the mammalian immune system and, thus, to enhance the already significant contribution of chickens toward understanding the evolution of immunity. The availability of the chicken genome sequence provides the opportunity to resolve outstanding questions concerning which molecular components of the immune system are shared between mammals and birds and which represent their unique evolutionary solutions. We have integrated genome data with existing knowledge to make a new comparative census of members of cytokine and chemokine gene families, distinguishing the core set of molecules likely to be common to all higher vertebrates from those particular to these 300 million-year-old lineages. Some differences can be explained by the different architectures of the mammalian and avian immune systems. Chickens lack lymph nodes and also the genes for the lymphotoxins and lymphotoxin receptors. The lack of functional eosinophils correlates with the absence of the eotaxin genes and our previously reported observation that interleukin- 5 (IL-5) is a pseudogene. To summarize, in the chicken genome, we can identify the genes for 23 ILs, 8 type I interferons (IFNs), IFN-gamma, 1 colony-stimulating factor (GM-CSF), 2 of the 3 known transforming growth factors (TGFs), 24 chemokines (1 XCL, 14 CCL, 8 CXCL, and 1 CX3CL), and 10 tumor necrosis factor superfamily (TNFSF) members. Receptor genes present in the genome suggest the likely presence of 2 other ILs, 1 other CSF, and 2 other TNFSF members.

Determination and Characterization of Bovine Interleukin-17 cDNA

Interleukin-17 (IL-17) is a proinflammatory cytokine produced by activated memory T cells, and it appears to play an upstream role in T cell-triggered inflammation by stimulating stromal cells to secrete other cytokines. We hypothesize that IL-17 plays a role in the recruitment of neutrophils in the bovine mammary gland during infection or immune-mediated inflammation. The rapid amplification of cDNA ends (RACE) method was used to obtain a cDNA of bovine IL-17 (BoIL-17) containing a 462-bp open reading frame (ORF) encoding a protein of 153 amino acids (aa) with a molecular mass of 17.2 kDa, a 23-residue NH(2)-terminal signal peptide, a single potential N-linked glycosylation site, and 6 cysteine residues. BoIL-17 protein shared 73.5% identity with the human protein and 67% with the mouse and rat proteins. Sf9 insect cells were transfected with BoIL-17 cDNA, and supernatant was tested for biologic activity on a primary culture of bovine mammary epithelial cells (MECs). mRNA synthesis of IL-6, IL-8, and growth-related oncogene alpha (Groalpha) was induced, suggesting a functional role for IL-17 in mammary immunity.

EMBRYO VACCINATION AGAINST EIMERIA TENELLA AND E. ACERVULINA INFECTIONS USING RECOMBINANT PROTEINS AND CYTOKINE ADJUVANTS

Avian coccidiosis is an intestinal disease caused by protozoa of the genus Eimeria. To investigate the potential of recombinant protein vaccines to control coccidiosis, we cloned 2 Eimeria sp. genes (EtMIC2 and 3-1E), expressed and purified their encoded proteins, and determined the efficacy of in ovo immunization to protect against Eimeria infections. Immunogen-specific serum antibody titers, parasite fecal shedding, and body weight gains were measured as parameters of disease. When administered alone, the recombinant EtMIC2 gene product induced significantly higher antibody responses, lower oocyst fecal shedding, and increased weight gains compared with nonvaccinated controls following infection with E. tenella. Combined embryo immunization with the EtMIC2 protein plus chicken cytokine or chemokine genes demonstrated that all 3 parameters of vaccination were improved compared with those of EtMIC2 alone. In particular, covaccination with EtMIC2 plus interleukin (IL)-8, IL-16, transforming growth factor-beta4, or lymphotactin significantly decreased oocyst shedding and improved weight gains beyond those achieved by EtMIC2 alone. Finally, individual vaccination with either EtMIC2 or 3-1E stimulated protection against infection by the heterologous parasite E. acervulina. Taken together, these results indicate that in ovo vaccination with the EtMIC2 protein plus cytokine/chemokine genes may be an effective method to control coccidiosis.

Resistance to intestinal coccidiosis following DNA immunization with the cloned 3-1E Eimeria gene plus IL-2, IL-15, and IFN-gamma

A cloned Eimeria acervulina gene (3-1E) was used to vaccinate chickens in ovo against coccidiosis, both alone and in combination with genes encoding interleukin (IL)-1, IL-2, IL-6, IL-8, IL-15, IL-16, IL-17, IL-18, or interferon (IFN)-gamma. Vaccination efficacy was assessed by increased serum anti-3-1E antibody titers, reduced fecal oocyst shedding, and enhanced body weight gain following experimental infection with E. acervulina. When used alone, anti-3-1E antibody titers were transiently, but reproducibly, increased at 2 wk and 3 wk posthatching in a dose-dependent manner. Similarly, significantly reduced oocyst shedding and increased weight gain were observed at relatively high-dose 3-1E vaccinations (> or =25 microg/egg). Combined immunization with the 3-1E and IL-1, IL-2, IL-15, or IFN-gamma genes induced higher serum antibody responses compared with immunization with 3-1E alone. Following parasite infection, chickens hatched from embryos given the 3-1E gene plus the IL-2 or IL-15 genes displayed significantly reduced oocyst shedding compared with those given 3-1E alone, while 3-1E plus IL-15 or IFN-gamma significantly increased weight gain compared with administration of 3-1E alone. Taken together, these results indicate that in ovo immunization with a recombinant Eimeria gene in conjunction with cytokine adjuvants stimulates protective intestinal immunity against coccidiosis.

Recent advances in immunomodulation and vaccination strategies against coccidiosis

Coccidiosis is a ubiquitous intestinal protozoan infection of poultry seriously impairing the growth and feed utilization of infected animals. Conventional disease control strategies rely heavily on chemoprophylaxis, which is a tremendous cost to the industry. Existing vaccines consist of live virulent or attenuated Eimeria strains with limited scope of protection against an ever-evolving and widespread pathogen. The continual emergence of drug-resistant strains of Eimeria, coupled with the increasing regulations and bans on the use of anticoccidial drugs in commercial poultry production, urges the need for novel approaches and alternative control strategies. Because of the complexity of the host immunity and the parasite life cycle, a comprehensive understanding of host-parasite interactions and protective immune mechanisms becomes necessary for successful prevention and control practices. Recent progress in functional genomics technology would facilitate the identification and characterization of host genes involved in immune responses as well as parasite genes and proteins that elicit protective host responses. This study reviews recent coccidiosis research and provides information on host immunity, immunomodulation, and the latest advances in live and recombinant vaccine development against coccidiosis. Such information will help magnify our understanding of host-parasite biology and mucosal immunology, and we hope it will lead to comprehensive designs of nutritional interventions and vaccination strategies for coccidiosis.

Cloning and characterization of Swine interleukin-17, preferentially expressed in the intestines

Interleukin-17 (IL-17), initially reported as CTLA-8, is a proinflammatory cytokine produced mainly by activated T cells. In the present study, the cDNA of a swine IL-17 (PoIL-17) gene was cloned from activated neonatal thymocytes, and the recombinant PoIL-17 (rPoIL-17) was biologically characterized. The complete open reading frame (ORF) of PoIL-17 contains 462-bp coding deduced 153 amino acid residues, with a calculated molecular weight of 17.3 kDa. The amino acid sequence showed 72.9%, 64.9%, 64.7%, 60.1%, and 47.4% similarities with that of human, rat, mouse, Herpesvirus saimiri ORF 13, and chicken, respectively. The six cysteine residues conserved over species including the virus were observed in PoIL-17. We successfully prepared the recombinant mature form of PoIL-17 and analyzed its biologic activities for swine splenocytes. RT-PCR analysis revealed a marked upregulation of expression of IL-1beta, IL-8, tumor necrosis factor-alpha (TNF-alpha), granulocyte colony-stimulating factor (G-CSF), and monocyte chemotactic protein-1 (MCP-1) mRNA expression in splenocytes treated with 100 ng/ml rPoIL-17 for 3 h. Furthermore, a swine chemokine, alveolar macrophage-derived neutrophil chemotactic factor II (AMCF-II), which was classified into the CXC subfamily was also augmented in mRNA level. This evidence indicates that recombinat PoIL-17 expressed in Escherichia coli was biologically active and exerted similar effects to those of a human (HuIL-17) and murine IL-17 (MuIL-17). The PoIL-17 mRNA is strongly expressed in the adult heart, skin, and, interestingly, intestinal tissues, including mesenteric lymph nodes but is restricted in neonatal tissues by using real-time quantitative RT-PCR. The gene sequence and biologically active recombinat protein for PoIL-17 will be useful for elucidation of the role of IL-17 in the regulation of intestinal immune responses.

Protective immunity against Eimeria acervulina following in ovo immunization with a recombinant subunit vaccine and cytokine genes

A purified recombinant protein from Eimeria acervulina (3-1E) was used to vaccinate chickens in ovo against coccidiosis both alone and in combination with expression plasmids encoding the interleukin 1 (IL-1), IL-2, IL-6, IL-8, IL-15, IL-16, IL-17, IL-18, or gamma interferon (IFN-gamma) gene. When used alone, vaccination with 100 or 500 mug of 3-1E resulted in significantly decreased oocyst shedding compared with that in nonvaccinated chickens. Simultaneous vaccination of the 3-1E protein with the IL-1, -15, -16, or -17 gene induced higher serum antibody responses than 3-1E alone. To evaluate protective intestinal immunity, vaccinated birds were challenged with live E. acervulina oocysts 14 days posthatch, and fecal-oocyst shedding and body weight gain were determined as parameters of coccidiosis. Chickens vaccinated with 3-1E protein showed significantly lower oocyst shedding and normal body weight gain than nonvaccinated and infected controls. Simultaneous immunization with 3-1E and the IL-2, -15, -17, or -18 or IFN-gamma gene further reduced oocyst shedding compared with that achieved with 3-1E alone. These results provide the first evidence that in ovo vaccination with the recombinant 3-1E Eimeria protein induces protective intestinal immunity against coccidiosis, and this effect was enhanced by coadministration of genes encoding immunity-related cytokines.

Immune modulation of the pulmonary hypertensive response to bacterial lipopolysaccharide (endotoxin) in broilers

The lungs of broilers are constantly challenged with lipopolysaccharide (LPS, endotoxin) that can activate leukocytes and trigger thromboxane A2 (TxA2)- and serotonin (5HT)-mediated pulmonary vasoconstriction leading to pulmonary hypertension. Among broilers from a single genetic line, some individuals respond to LPS with large increases in pulmonary arterial pressure, whereas others fail to exhibit any response to the same supramaximal dose of LPS. This extreme variability in the pulmonary hypertensive response to LPS appears to reflect variability in the types or proportions of chemical mediators released by leukocytes. Our research has confirmed that TxA2 and 5HT are potent pulmonary vasoconstrictors in broilers and that broilers hatched and reared together consistently exhibit pulmonary hypertension after i.v. injections of TxA2 or 5HT. Previous in vitro studies conducted using macrophages from different lines of chickens demonstrated innate variability in the LPS-stimulated induction of nitric oxide synthase (iNOS) followed by the onset of an LPS-refractory state. The NOS enzyme converts arginine to citrulline and nitric oxide (NO). It is known that NO produced by endothelial NOS serves as a key modulator of flow-dependent pulmonary vasodilation, and it is likely that NO generated by iNOS also contributes to the pulmonary vasodilator response. Accordingly, it is our hypothesis that the pulmonary hypertensive response to LPS in broilers is minimal when more vasodilators (NO, prostacyclin) than vasoconstrictors (TxA2, 5HT) are generated during an LPS challenge. Indeed, inhibiting NO production through pharmacological blockade of NOS with the inhibitor Nomega-nitro-L-arginine methyl ester modestly increased the baseline pulmonary arterial pressure and dramatically increased the pulmonary hypertensive response to LPS in all broilers evaluated. Innate differences in the effect of LPS on the pulmonary vasculature may contribute to differences in susceptibility of broilers to pulmonary hypertension syndrome (ascites).