Molecular and functional characterization of turkey interferon

Evolution of developmental and comparative immunology in poultry: The regulators and the regulated

Avian has a unique immune system that evolved in response to environmental pressures in all aspects of innate and adaptive immune responses, including localized and circulating lymphocytes, diversity of immunoglobulin repertoire, and various cytokines and chemokines. All of these attributes make birds an indispensable vertebrate model for studying the fundamental immunological concepts and comparative immunology. However, research on the immune system in birds lags far behind that of humans, mice, and other agricultural animal species, and limited immune tools have hindered the adequate application of birds as disease models for mammalian systems. An in-depth understanding of the avian immune system relies on the detailed studies of various regulated and regulatory mediators, such as cell surface antigens, cytokines, and chemokines. Here, we review current knowledge centered on the roles of avian cell surface antigens, cytokines, chemokines, and beyond. Moreover, we provide an update on recent progress in this rapidly developing field of study with respect to the availability of immune reagents that will facilitate the study of regulatory and regulated components of poultry immunity. The new information on avian immunity and available immune tools will benefit avian researchers and evolutionary biologists in conducting fundamental and applied research.

Characterization of agapornis fischeri interferon gamma and its activity against beak and feather disease virus

This study sought to clone and sequence the interferon-γ (IFN-γ) gene of the Fischer's lovebird parrot (Agapornis fischeri). Raw264.7 cells treated with the expressed IFN-γ protein exhibited an upregulation in inducible nitric oxide synthase protein expression and nitric oxide (NO) production coupled with increases in phagocytosis and pinocytosis, as well as an induction of interferon-stimulated genes through the activation of the NF-κB factor, all of which are indicators of the innate immune responses of the activated macrophages. Similar to the IFN-γ protein of other species, the NO production activity of the parrot IFN-γ protein decreased by 80% after exposure at 60 °C for 4 min. Additionally, only half of the NO production activity of the parrot IFN-γ protein remained upon exposure to HCl for 30 min. These findings suggested that the parrot IFN-γ protein was heat-labile and sensitive to acidic conditions. Therefore, all of these effects contributed to the blockage of the uptake of BFDV virus-like particles (VLPs) by cells, the nuclear entry of the Cap protein of BFDV VLPs, and the clearance of the virus from BFDV-infected parrots by the IFN-γ protein of Agapornis fischeri. This study is the first to describe the cloning of the IFN-γ gene of Agapornis fischeri and characterize the anti-beak and feather disease virus activity of the IFN-γ protein of Agapornis fischeri.

The Arabian camel, Camelus dromedarius interferon epsilon: Functional expression, in vitro refolding, purification and cytotoxicity on breast cancer cell lines

The current study highlights, for the first time, cloning, overexpression and purification of the novel interferon epsilon (IFNƐ), from the Arabian camel Camelus dromedaries. The study then assesses the cytotoxicity of IFNε against two human breast cancer cell lines MDA-MB-231 and MCF-7. Full-length cDNA encoding interferon epsilon (IFNε) was isolated and cloned from the liver of the Arabian camel, C. dromedarius using reverse transcription-polymerase chain reaction. The sequence analysis of the camel IFNε cDNA showed a 582-bp open reading frame encoding a protein of 193 amino acids with an estimated molecular weight of 21.230 kDa. A BLAST search analysis revealed that the C. dromedarius IFNε shared high sequence identity with the IFN genes of other species, such as Camelus ferus, Vicugna pacos, and Homo sapiens. Expression of the camel IFNε cDNA in Escherichia coli gave a fusion protein band of 24.97 kDa after induction with either isopropyl β-D-1-thiogalactopyranoside or lactose for 5 h. Recombinant IFNε protein was overexpressed in the form of inclusion bodies that were easily solubilized and refolded using SDS and KCl. The solubilized inclusion bodies were purified to apparent homogeneity using nickel affinity chromatography. We examined the effect of IFNε on two breast cancer cell lines MDA-MB-231 and MCF-7. In both cell lines, IFNε inhibited cell survival in a dose dependent manner as observed by MTT assay, morphological changes and apoptosis assay. Caspase-3 expression level was found to be increased in MDA-MB-231 treated cells as compared to untreated cells.

Avian Interferons and Their Antiviral Effectors

Interferon (IFN) responses, mediated by a myriad of IFN-stimulated genes (ISGs), are the most profound innate immune responses against viruses. Cumulatively, these IFN effectors establish a multilayered antiviral state to safeguard the host against invading viral pathogens. Considerable genetic and functional characterizations of mammalian IFNs and their effectors have been made, and our understanding on the avian IFNs has started to expand. Similar to mammalian counterparts, three types of IFNs have been genetically characterized in most avian species with available annotated genomes. Intriguingly, chickens are capable of mounting potent innate immune responses upon various stimuli in the absence of essential components of IFN pathways including retinoic acid-inducible gene I, IFN regulatory factor 3 (IRF3), and possibility IRF9. Understanding these unique properties of the chicken IFN system would propose valuable targets for the development of potential therapeutics for a broader range of viruses of both veterinary and zoonotic importance. This review outlines recent developments in the roles of avian IFNs and ISGs against viruses and highlights important areas of research toward our understanding of the antiviral functions of IFN effectors against viral infections in birds.

Avian metapneumovirus infection of chicken and turkey tracheal organ cultures: comparison of virus-host interactions

Avian metapneumovirus (aMPV) is a pathogen with worldwide distribution, which can cause high economic losses in infected poultry. aMPV mainly causes infection of the upper respiratory tract in both chickens and turkeys, although turkeys seem to be more susceptible. Little is known about virus-host interactions at epithelial surfaces after aMPV infection. Tracheal organ cultures (TOC) are a suitable model to investigate virus-host interaction in the respiratory epithelium. Therefore, we investigated virus replication rates and lesion development in chicken and turkey TOC after infection with a virulent aMPV subtype A strain. Aspects of the innate immune response, such as interferon-α and inducible nitric oxide synthase mRNA expression, as well as virus-induced apoptosis were determined. The aMPV-replication rate was higher in turkey (TTOC) compared to chicken TOC (CTOC) (P < 0.05), providing circumstantial evidence that indeed turkeys may be more susceptible. The interferon-α response was down-regulated from 2 to 144 hours post infection in both species compared to virus-free controls (P < 0.05); this was more significant for CTOC than TTOC. Inducible nitric oxide synthase expression was significantly up-regulated in aMPV-A-infected TTOC and CTOC compared to virus-free controls (P < 0.05). However, the results suggest that NO may play a different role in aMPV pathogenesis between turkeys and chickens as indicated by differences in apoptosis rate and lesion development between species. Overall, our study reveals differences in innate immune response regulation and therefore may explain differences in aMPV - A replication rates between infected TTOC and CTOC, which subsequently lead to more severe clinical signs and a higher rate of secondary infections in turkeys.

Cross-Species Antiviral Activity of Goose Interferons against Duck Plague Virus Is Related to Its Positive Self-Feedback Regulation and Subsequent Interferon Stimulated Genes Induction

Interferons are a group of antiviral cytokines acting as the first line of defense in the antiviral immunity. Here, we describe the antiviral activity of goose type I interferon (IFNα) and type II interferon (IFNγ) against duck plague virus (DPV). Recombinant goose IFNα and IFNγ proteins of approximately 20 kDa and 18 kDa, respectively, were expressed. Following DPV-enhanced green fluorescent protein (EGFP) infection of duck embryo fibroblast cells (DEFs) with IFNα and IFNγ pre-treatment, the number of viral gene copies decreased more than 100-fold, with viral titers dropping approximately 100-fold. Compared to the control, DPV-EGFP cell positivity was decreased by goose IFNα and IFNγ at 36 hpi (3.89%; 0.79%) and 48 hpi (17.05%; 5.58%). In accordance with interferon-stimulated genes being the “workhorse” of IFN activity, the expression of duck myxovirus resistance (Mx) and oligoadenylate synthetases-like (OASL) was significantly upregulated (p < 0.001) by IFN treatment for 24 h. Interestingly, duck cells and goose cells showed a similar trend of increased ISG expression after goose IFNα and IFNγ pretreatment. Another interesting observation is that the positive feedback regulation of type I IFN and type II IFN by goose IFNα and IFNγ was confirmed in waterfowl for the first time. These results suggest that the antiviral activities of goose IFNα and IFNγ can likely be attributed to the potency with which downstream genes are induced by interferon. These findings will contribute to our understanding of the functional significance of the interferon antiviral system in aquatic birds and to the development of interferon-based prophylactic and therapeutic approaches against viral disease.

Interferons and Their Receptors in Birds: A Comparison of Gene Structure, Phylogenetic Analysis, and Cross Modulation

Interferon may be thought of as a key, with the interferon receptor as the signal lock: Crosstalk between them maintains their balance during viral infection. In this review, the protein structure of avian interferon and the interferon receptor are discussed, indicating remarkable similarity between different species. However, the structures of the interferon receptors are more sophisticated than those of the interferons, suggesting that the interferon receptor is a more complicated signal lock system and has considerable diversity in subtypes or structures. Preliminary evolutionary analysis showed that the subunits of the interferon receptor formed a distinct clade, and the orthologs may be derived from the same ancestor. Furthermore, the development of interferons and interferon receptors in birds may be related to an animal’s age and the maintenance of a balanced state. In addition, the equilibrium between interferon and its receptor during pathological and physiological states revealed that the virus and the host influence this equilibrium. Birds could represent an important model for studies on interferon’s antiviral activities and may provide the basis for new antiviral strategies.

Cloning, expression and antiviral bioactivity of red-crowned crane interferon-α

Interferon-α (IFN-α) genes have been cloned from a variety of animals, but information regarding crane IFN-α has not been reported to date. In this study, we cloned a full-length Red-crowned Crane interferon-α (crIFN-α) gene sequence consisting of a 486bp partial 5' UTR, 741bp complete ORF and 559bp partial 3' UTR. This gene encodes a protein of 246 amino acids and shares 60 to 80% identity with avian IFN-α and less than 45% identity with mammalian IFN-α. The expression of crIFN-α with an N-terminal His-tag was investigated in Escherichia coli, and the protein was purified on a nickel column. To obtain activated proteins, crIFN-α inclusion bodies were renatured by dialysis. In vitro cytopathic inhibition assays indicated that the recombinant crIFN-α could inhibit the replication of vesicular stomatitis virus in chicken fibroblasts. These antiviral activities were abrogated by rabbit anti-crIFN-α antibodies in vitro. In addition, an immunofluorescence assay indicated that crIFN-α could be expressed in chicken fibroblasts and was primarily located in the cytoplasm. Taken together, our results suggest that the crIFN-α gene may play an important role in inhibiting the replication of viruses.

Reassortment of NS segments modifies highly pathogenic avian influenza virus interaction with avian hosts and host cells

Highly pathogenic avian influenza viruses (HPAIV) of subtypes H5 and H7 have caused numerous outbreaks in diverse poultry species and rising numbers of human infections. Both HPAIV subtypes support a growing concern of a pandemic outbreak, specifically via the avian-human link. Natural reassortment of both HPAIV subtypes is a possible event with unpredictable outcome for virulence and host specificity of the progeny virus for avian and mammalian species. NS reassortment of H5N1 HPAIV viruses in the background of A/FPV/Rostock/1934 (H7N1) HPAIV has been shown to change virus replication kinetics and host cell responses in mammalian cells. However, not much is known about the virus-host interaction of such viruses in avian species. In the present study, we show that the NS segment of A/Vietnam/1203/2004 (FPV NS VN, H5N1) HPAIV significantly altered the characteristics of the H7 prototype HPAIV in tracheal organ cultures (TOC) of chicken and turkey in vitro, with decreased replication efficiency accompanied by increased induction of type I interferon (IFN) and apoptosis. Furthermore, species-specific differences between chicken and turkey were demonstrated. Interestingly, NS-reassortant FPV NS VN showed an overall highly pathogenic phenotype, with increased virulence and replication potential compared to the wild-type virus after systemic infection of chicken and turkey embryos. Our data demonstrate that single reassortment of an H5-type NS into an H7-type HPAIV significantly changed virus replication abilities and influenced the avian host cell response without prior adaptation.

Development of reagents to study the turkey's immune response: cloning and characterisation of two turkey cytokines, interleukin (IL)-10 and IL-13

The cDNAs of two turkey cytokines, interleukin (IL)-10 and IL-13, were cloned using oligonucleotide primers designed from their chicken orthologues. The coding regions of the chicken and turkey genes are highly conserved, with IL-10 and IL-13 exhibiting 94.1% and 90% nucleotide and 92% and 79.9% amino acid identity respectively. Both showed consistent mRNA expression in turkey lymphoid and gut tissues. Expression in non-lymphoid tissues was more variable but generally highest in the skin and trachea. Recombinant turkey IL-10 was expressed and bioactivity demonstrated by inhibition of IFN-γ synthesis from activated splenocytes. Chicken and turkey IL-10 cross-reacted in functional assays.

Chicken interferon alpha pretreatment reduces virus replication of pandemic H1N1 and H5N9 avian influenza viruses in lung cell cultures from different avian species

BACKGROUND

Type I interferons, including interferon alpha (IFN-α), represent one of the first lines of innate immune defense against influenza virus infection. Following natural infection of chickens with avian influenza virus (AIV), transcription of IFN-α is quickly up regulated along with multiple other immune-related genes. Chicken IFN-α up regulates a number of important anti-viral response genes and has been demonstrated to be an important cytokine to establish anti-viral immunity. However, the mechanisms by which interferon inhibit virus replication in avian species remains unknown as does the biological activity of chicken interferon in other avian species.

METHODS

In these studies, we assessed the protective potential of exogenous chicken IFN-α applied to chicken, duck, and turkey primary lung cell cultures prior to infection with the pandemic H1N1 virus (A/turkey/Virginia/SEP-4/2009) and an established avian H5N9 virus (A/turkey/Wisconsin/1968). Growth kinetics and induction of select immune response genes, including IFN-α and myxovirus-resistance gene I (Mx), as well as proinflammatory cytokines (IL-1β and IL-6), were measured in response to chicken IFN-α and viral infection over time.

RESULTS

Results demonstrate that pretreatment with chicken IFN-α before AIV infection significantly reduced virus replication in both chicken-and turkey-origin lung cells and to a lesser degree the duck-origin cells. Virus growth was reduced by approximately 200-fold in chicken and turkey cells and 30-fold in duck cells after 48 hours of incubation. Interferon treatment also significantly decreased the interferon and proinflammatory response during viral infection. In general, infection with the H1N1 virus resulted in an attenuated interferon and proinflammatory response in these cell lines, compared to the H5N9 virus.

CONCLUSIONS

Taken together, these studies show that chicken IFN-α reduces virus replication, lower host innate immune response following infection, and is biologically active in other avian species.

Interferon Alpha Characterization and Its Comparative Expression in PBM Cells of Capra hircus and Antelope cervicapra Cultured in the Presence of TLR9 Agonist

TLR9 plays pivotal role in innate immune responses through upregulation of costimulatory molecules and induction of proinflammatory cytokines like type I interferons including interferon alpha (IFNA). The present study characterized IFNA cDNA and predicted protein sequences in goat and black buck. Response of the PBM cells to TLR9 agonist CpG ODN C and Phorbol Myristate Acetate (PMA) was evaluated by realtime PCR. IFNA coding sequences were amplified from leukocyte cDNA and cloned in pGEMT-easy vector for nucleotide sequencing. Sequence analysis revealed 570 bp, IFNA ORF encoding 189 amino acids in goat and black buck. Black buck and goat IFNA has 92.1% to 94.7% and 93% to 95.6% similarity at nucleotide level, 86.3% to 89.5% and 70.9% to 91.6% identity at amino acid level with other ruminants, respectively. Nonsynonymous substitutions exceeding synonymous substitutions indicated IFNA evolved through positive selection among ruminants. In spite of lower total leukocyte count, the innate immune cells like monocytes and neutrophils were more in black buck compared to goat. In addition, CpG ODN C-stimulated PBM cells revealed raised IFNA transcript in black buck than goat. These findings indicate sturdy genetically governed immune system in wild antelope black buck compared to domestic ruminant goat.

Cloning and expression of pigeon IFN-γ gene

This is the first paper describing the cloning of pigeon IFN-γ gene (PiIFN-γ) and the analysis of the in vitro expressed recombinant protein. The PiIFN-γ gene was identified by RT-PCR as a 498bp, fragment coding for a precursor protein of 165 amino acids instead of 164 amino acids, as observed in the other avian species. The recombinant protein was expressed in vitro by an eukaryotic system and the biological properties of the cytokine were tested using a chicken macrophage cell line. The high degree of amino acid and nucleotide identity, shared with the ChIFN-γ, and the fact that the pigeon protein was functional on chicken cells, indicates a cross-reactivity between pigeon and chicken IFN-γ. The detection of the PiIFN-γ could represent an useful instrument in understanding the role played by this cytokine in immune response related to vaccinations and infectious diseases in the pigeon.

Super-sentinel chickens and detection of low-pathogenicity influenza virus

Chicken interferon-alpha administered perorally in drinking water acts on the oropharyngeal mucosal system as an adjuvant that causes chickens to rapidly seroconvert after natural infection by low-pathogenicity Influenza virus. These chickens, termed super sentinels, can serve as sensitive early detectors of clinically inapparent infections.

Structural and functional homology among chicken, duck, goose, turkey and pigeon interleukin-8 proteins

Interleukin (IL)-8-encoding regions of five avian species were cloned, sequenced and characterized. Each IL-8-encoding region is 312 nucleotides long and encodes IL-8 which is 103 amino acids. Pairwise sequence analysis showed that sequence identities of IL-8-encoding regions ranged from 87% to 100%. The IL-8 protein identities varied from 84% to 100%. Phylogenetic analysis indicated that IL-8-encoding regions and encoded proteins of chicken, duck, goose and turkey clustered together and evolved into a distinct phylogenetic lineage from that of pigeon which evolved into a second lineage. The results from binding reactivities of antiserum against each recombinant IL-8 (rIL-8) protein to homologous or heterologous rIL-8 proteins, chemotactic activities of each rIL-8 protein or reduction levels of the chemotactic activity of rIL-8 protein which was pretreated with homologous or heterlogous antiserum have suggested that all five IL-8 proteins were functionally active, and shared structural and functional identity with each other.

Induction of local and systemic immune reactions following infection of turkeys with avian Metapneumovirus (aMPV) subtypes A and B

Most of the studies regarding the immunopathogenesis of avian Metapneumovirus (aMPV) have been done with subtype C of aMPV. Not much is known about the immunopathogenesis of aMPV subtypes A and B in turkeys. Specifically, local immune reactions have not been investigated yet. We conducted two experiments in commercial turkeys. We investigated local and systemic humoral and cell mediated immune reactions following infection with an attenuated vaccine strain of aMPV subtype B (Experiment I) and virulent strains of aMPV subtypes A and B (Experiment II). Turkeys infected with virulent aMPV strains developed mild respiratory signs while birds inoculated with the attenuated aMPV did not show any clinical signs. Virus neutralizing antibodies were detected locally in tracheal washes and systemically in serum as soon as 5-7 days post aMPV infection (PI) independent of the strain used. Virus neutralizing antibody titres peaked at 7 days PI and then antibody levels declined. The peak of serum ELISA antibody production varied between infected groups and ranged from 14 and 28 days PI. All aMPV strains induced an increase in the percentage of CD4+ T cell populations in spleen and Harderian gland at days 7 or 14 PI. Furthermore, as shown in Experiment I, infection with the attenuated aMPV-B strain stimulated spleen leukocytes to release significantly higher levels of interferons (IFNs), interleukin-6 and nitric oxide in ex vivo culture in comparison to virus-free controls up to 7 days PI (P<0.05). As detected by quantitative real time RT-PCR in Experiment II, infection with virulent aMPV induced an increased IFNgamma expression in the Harderian gland in comparison to virus-free controls. IFNgamma expression in the spleen varied between aMPV strains and days PI. Overall, our study demonstrates that aMPV subtypes A and B infection induced humoral and cell mediated immune reactions comparable to subtype C infections. We observed only temporary stimulation of serum virus neutralizing antibodies and of most of the local immune reactions independent of the aMPV strain used. The temporary character of immune reactions may explain the short duration of protection against challenge following aMPV vaccination in the field.

Evolution of the Class 2 cytokines and receptors, and discovery of new friends and relatives

The sequencing of a wide variety of genomes and their transcripts has allowed researchers to determine how proteins or protein families evolved and how strongly during evolution a protein has been conserved. In this report, we analyze the evolution of the Class 2 ligands and their cognate receptors by analyzing Class 2 ligand and receptor chain gene sequences from a variety of DNA sequence databases. Both the Class 2 cytokines and receptor chains appear to have developed during the evolution of the chordate phyla: distant homologues of type I interferon (IFN) receptors are the only Class 2 cytokine receptors identified in the Ciona genomes, while a wide variety of Class 2 ligands and receptor chains are encoded in the currently available genomes of bony vertebrates (teleost fish, amphibians, reptiles, birds, mammals). Phylogenetic trees of ligands and ligand-binding receptor chains demonstrate that proteins involved in conferring antiviral activity diverged before those involved in adaptive immunity. Genes encoding IFNs and IFN receptors duplicated multiple times during chordate evolution, suggesting that duplication of genes encoding IFN activity conveyed an evolutionary advantage. Altogether, these data support a model whereby the original Class 2 cytokines and receptors evolved and duplicated during the evolution of the chordate innate immune response system; new receptor and ligand duplications evolved into signaling molecules to fulfill communication requirements of a highly specialized and differentiated vertebrate immune system. In addition, the genomic analysis led to the discovery of some new members of this family.

Interferons, interferon-like cytokines, and their receptors

Recombinant interferon-alpha (IFN-alpha) was approved by regulatory agencies in many countries in 1986. As the first biotherapeutic approved, IFN-alpha paved the way for the development of many other cytokines and growth factors. Nevertheless, understanding the functions of the multitude of human IFNs and IFN-like cytokines has just touched the surface. This review summarizes the history of the purification of human IFNs and the key aspects of our current state of knowledge of human IFN genes, proteins, and receptors. All the known IFNs and IFN-like cytokines are described [IFN-alpha, IFN-beta, IFN-epsilon, IFN-kappa, IFN-omega, IFN-delta, IFN-tau, IFN-gamma, limitin, interleukin-28A (IL-28A), IL-28B, and IL-29] as well as their receptors and signal transduction pathways. The biological activities and clinical applications of the proteins are discussed. An extensive section on the evolution of these molecules provides some new insights into the development of these proteins as major elements of innate immunity. The overall structure of the IFNs is put into perspective in relation to their receptors and functions.

Characterization of snakehead rhabdovirus infection in zebrafish (Danio rerio)

The zebrafish, Danio rerio, has become recognized as a valuable model for the study of development, genetics, and toxicology. Recently, the zebrafish has been recognized as a useful model for infectious disease and immunity. In this study, the pathogenesis and antiviral immune response of zebrafish to experimental snakehead rhabdovirus (SHRV) infection was characterized. Zebrafish 24 h postfertilization to 30 days postfertilization were susceptible to infection by immersion in 10(6) 50% tissue culture infective doses (TCID50) of SHRV/ml, and adult zebrafish were susceptible to infection by intraperitoneal (i.p.) injection of 10(5) TCID50 of SHRV/ml. Mortalities exceeded 40% in infected fish, and clinical presentation of infection included petechial hemorrhaging, redness of the abdomen, and erratic swim behavior. Virus reisolation and reverse transcription-PCR analysis of the viral nucleocapsid gene confirmed the presence of SHRV. Histological sections of moribund embryonic and juvenile fish revealed necrosis of the pharyngeal epithelium and liver, in addition to congestion of the swim bladder by cell debris. Histopathology in adult fish injected i.p. was confined to the site of injection. The antiviral response in zebrafish was monitored by quantitative real-time PCR analysis of zebrafish interferon (IFN) and Mx expression. IFN and Mx levels were elevated in zebrafish exposed to SHRV, although expression and intensity differed with age and route of infection. This study is the first to examine the pathogenesis of SHRV infection in zebrafish. Furthermore, this study is the first to describe experimental infection of zebrafish embryos with a viral pathogen, which will be important for future experiments involving targeted gene disruption and forward genetic screens.

The Interferon-α Genes from Three Chicken Lines and Its Effects on H9N2 Influenza Viruses

The interferon-alpha genes from three chicken lines were cloned by a direct PCR technique, and the effects of recombinant protein expressed in a prokaryotic system on highly pathogenic H9N2 influenza viruses were investigated. The cloned ChIFN-alpha gene encoded a protein of 193 amino acids with a signal sequence of 31 amino acids and mature peptides of 162 amino acids. Comparison of ChIFN-alpha sequences, detected six amino acids substitutions at positions 50, 58, 65, 81, 181, and 183. Homology analysis indicated that ChIFN-alpha genes could be subdivided into two lineages, SH-ChIFN-alpha and WJ-ChIFN-alpha. In addition, both SH-ChIFN-alpha and WJ-ChIFN-alpha were expressed with the N-terminal 6 consecutive histidine residues in a high-level prokaryotic expression system. Recombinant chicken interferon-alpha (rChIFN-alpha) protein has anti-VSV activity of more than 1 x 10(8) U/mg. Moreover, High concentration (10,000U) of rSH-ChIFN-alpha resulted in over 40% inhibition of the H9N2 virus infection in chicken embryos (Ovo), and 100% inhibition from one day-old to five day-old chickens (Vivo). The results suggested that rChIFN-alpha is a potential agent against many Chicken viral strains.

Early in vivo cytokine genes expression in chickens after challenge with Salmonella typhimurium lipopolysaccharide and modulation by dietary n--3 polyunsaturated fatty acids

We studied the effects of Salmonella typhimurium lipopolysaccharide (LPS) on in vivo cytokine mRNA levels in chickens, and investigated whether these levels could be altered by different nutrients. Two hundred and forty chicks were assigned in a 2 x 4 factorial design of treatments. Factors were intravenous injection with S. typhimurium LPS, or saline (control), and four dietary fat sources: corn oil (CO), linseed oil (LO), menhaden oil and beef tallow (BT). Two hours after injection birds were killed and their spleens removed for RNA extraction. Quantitative real-time RT-PCR assays for mRNA of chicken IFN-gamma, IL-6, IL-8, IL-15, IL-18 and 28S rRNA were used to obtain the in vivo splenic cytokine profiles. Expression levels of IL-6, IL-8, IL-18 and IFN-gamma mRNA increased, but IL-15 mRNA decreased 2h after challenge with LPS compared with saline controls. In saline-injected control chickens, the dietary oil source did not affect the splenic mRNA level of any cytokine. In LPS challenged chickens IFN-gamma mRNA was significantly higher in the chickens fed the fish oil enriched diet compared with the LO, CO and BT enriched diets. The present data imply that avian IL-15 has, at least partially, a different function compared to its mammalian counterpart, and in addition, chicken innate immune responses might be affected differently by n-3 PUFA compared to mammals.

Molecular and functional analysis of an interferon gene from the zebrafish, Danio rerio

The interferon (IFN) family consisting of alpha IFN (IFN-alpha), IFN-beta, IFN-omega, IFN-delta, IFN-kappa, and IFN-tau is a large group of cytokines involved in the innate immune response against various microorganisms. Genes for IFN have been cloned from a variety of mammalian and avian species; however, IFN genes from lower-order vertebrates have not been forthcoming. Here, we report the cloning and characterization of the IFN gene from the zebrafish, Danio rerio. Zebrafish IFN (zfIFN) is 185 amino acids in length, with the first 22 amino acids representing a putative signal peptide. Treatment with the known IFN inducer polyinosinic acid-polycytidylic acid (poly[I]-poly[C]) resulted in an increase in zfIFN mRNA transcripts. zfIFN was also able to activate the IFN-inducible Mx promoter when cotransfected with a plasmid containing the zebrafish Mx promoter upstream of a luciferase reporter gene. To demonstrate antiviral activity, zebrafish cells were transfected with zfIFN and challenged with a fish rhabdovirus. A 36% reduction in plaque number was seen in zfIFN-transfected cells, compared to cells transfected with a control vector. Phylogenetic analysis has shown zfIFN to be approximately equally divergent from avian and mammalian IFN, consistent with its origin from an IFN present in the most recent common ancestor of these divergent lineages. A putative IFN from puffer, Fugu rubripes, was also found when zfIFN was used to search the fugu genome database, demonstrating that zfIFN can be used to find additional fish IFN genes. These results demonstrate that zebrafish can be used as an effective model for studying innate immunity and immune response to infectious disease.

Evolution of interleukin-1beta

All jawed vertebrates possess a complex immune system, which is capable of anticipatory and innate immune responses. Jawless vertebrates possess an equally complex immune system but with no evidence of an anticipatory immune response. From these findings it has been speculated that the initiation and regulation of the immune system within vertebrates will be equally complex, although very little has been done to look at the evolution of cytokine genes, despite well-known biological activities within vertebrates. In recent years, cytokines, which have been well characterised within mammals, have begun to be cloned and sequenced within non-mammalian vertebrates, with the number of cytokine sequences available from primitive vertebrates growing rapidly. The identification of cytokines, which are mammalian homologues, will give a better insight into where immune system communicators arose and may also reveal molecules, which are unique to certain organisms. Work has focussed on interleukin-1 (IL-1), a major mediator of inflammation which initiates and/or increases a wide variety of non-structural, function associated genes that are characteristically expressed during inflammation. Other than mammalian IL-1beta sequences there are now full cDNA sequences and genomic organisations available from bird, amphibian, bony fish and cartilaginous fish, with many of these genes having been obtained using an homology cloning approach. This review considers how the IL-1beta gene has changed through vertebrate evolution and whether its role and regulation are conserved within selected non-mammalian vertebrates.

Turkey and chicken interleukin-18 (IL18) share high sequence identity, but have different polyadenylation sites in their 3' UTR

The cDNA of turkey interleukin-18 (IL18) was cloned, initially using oligonucleotide primers based on the sequence of the chicken IL18 gene. The coding regions of the turkey and chicken IL18 genes are highly conserved (96.1% nucleotide identical and 97.4% amino acid identical). The 3' UTR of the turkey IL18 mRNA contains two 'instability' motifs and a canonical polyadenylation site, as compared to the chicken IL18 mRNA which contains only one instability motif and lacks a canonical polyadenylation site. Phylogenetic analysis shows that turkey and chicken IL18 have diverged to a less extent than IL18 from closely related mammalian species. We predict that turkey and chicken IL18 will cross-react in functional assays.

The emerging role of avian cytokines as immunotherapeutics and vaccine adjuvants

The use of antibiotic feed additives and chemical antimicrobials in food production animals is a double-edged sword. On one hand, it helps to prevent the outbreak of disease and promotes the growth of animals, but on the other hand, concerns are mounting over the emergence of antibiotic-resistant bacteria. As a consequence, some countries have already banned the use of in-feed antibiotics which has resulted in meat producers urgently seeking environmentally friendly alternative methods to control disease. Cytokines are proteins that control the type and extent of an immune response following infection or vaccination. They therefore represent excellent naturally occurring therapeutics. The use of cytokines in poultry has become more feasible with the discovery of a number of avian cytokine genes. Since the immune system of chickens is similar to that of mammals, they offer an attractive model system to study the effectiveness of cytokine therapy in the control of disease in livestock. This review will focus on the recent advances made in avian cytokines, with a particular focus on their assessment as therapeutic agents and vaccine adjuvants.

Molecular identification and characterization of turkey IFN-gamma gene

The cDNAs of turkey and chicken interferon gamma (IFN-gamma) were cloned and the functional activity of turkey and chicken IFN-gamma was compared. The coding region of turkey IFN-gamma gene encodes a predicted mature protein of 145 amino acids with a molecular weight at 16.8 kDa. Compared with type I IFN, the IFN-gamma between turkey and chicken also had the same size and high degree of identity at the nucleotide (96.0%) and amino acid (96.4%) sequence. Turkey IFN-gamma was cross-reactive with chicken cells. Both turkey and chicken IFN-gamma could induce production of nitric oxide by turkey or chicken macrophages. Turkey IFN-gamma also had similar degree of sensitivity to heat and pH 2.0 as chicken IFN-gamma. The functional activity of both turkey and chicken IFN-gamma could be neutralized by a monoclonal antibody specific to chicken IFN-gamma to a similar extent. These results indicated that IFN-gamma protein was cross-reactive between turkey and chicken.

Cytokines of birds: conserved functions--a largely different look

Targeted disruptions of the mouse genes for cytokines, cytokine receptors, or components of cytokine signaling cascades convincingly revealed the important roles of these molecules in immunologic processes. Cytokines are used at present as drugs to fight chronic microbial infections and cancer in humans, and they are being evaluated as immune response modifiers to improve vaccines. Until recently, only a few avian cytokines have been characterized, and potential applications thus have remained limited to mammals. Classic approaches to identify cytokine genes in birds proved difficult because sequence conservation is generally low. As new technology and high throughput sequencing became available, this situation changed quickly. We review here recent work that led to the identification of genes for the avian homologs of interferon-alpha/beta (IFN-alpha/beta) and IFN-gamma, various interleukins (IL), and several chemokines. From the initial data on the biochemical properties of these molecules, a picture is emerging that shows that avian and mammalian cytokines may perform similar tasks, although their primary structures in most cases are remarkably different.

Turkey and chicken interferon-gamma, which share high sequence identity, are biologically cross-reactive

Turkey and chicken interferon-gamma (IFN-gamma) share high identity (96.3% and 97% at the nucleotide and amino acid level, respectively). As such, we predicted that they would be functionally cross-reactive. To test this hypothesis, we produced recombinant turkey and chicken IFN-gamma, and compared their biological properties. Recombinant turkey and chicken IFN-gamma both induce HD11 cells (a chicken macrophage cell line) and LSTC-IAH30 cells (ALV-J-transformed turkey macrophages) to produce nitric oxide (NO), as measured in an avian IFN-gamma bioassay. Polyclonal and monoclonal antibodies, capable of neutralising the effect of chicken IFN-gamma on HD11 cells, were also shown to inhibit the activity of turkey IFN-gamma on these cells. The antibody neutralisation effect on both turkey and chicken IFN-gamma was shown by a significant reduction in NO production by HD11 cells when the neutralising antibodies were present in the bioassay. FACS analysis showed that HD11 and LSTC-IAH30 cells share some cell surface markers.

Transient resistance of influenza virus to interferon action attributed to random multiple packaging and activity of NS genes

Interferon (IFN) action survival curves for an avian influenza virus (AIV) in chicken or quail cells showed that 40-60% of the virions in a stock of virus were highly sensitive to the inhibitory effects of chicken IFN-alpha (ChIFN-alpha), whereas the rest were up to 100 times less sensitive. This greater resistance to IFN was transient, that is, was not a stable characteristic, in that virus stocks grown from plaques that formed in the presence of 50-800 U/ml IFN gave rise to virus populations that contained both sensitive and resistant virions. If AIV was serially passaged several times in the presence of IFN, the proportion of transiently IFN-resistant virus was greater. We propose a model to account for this transient resistance of AIV to IFN action based on the reported inactivation of the dsRNA-dependent protein kinase (PKR) and its activator dsRNA by the NS1 protein of influenza virus and also on the increase in the survival of AIV in IFN-treated cells exposed to 2-aminopurine, a known inhibitor of PKR. We suggest that IFN-resistant AIV is generated from a random packaging event that results in virions that contain two or more copies of RNA segment 8, the gene segment that encodes the NS1 protein of AIV, and that these virions will produce correspondingly elevated levels of NS1. The experimental data fit well to theoretical curves based on this model and constructed from the fraction of virus in the population expected by chance to contain one, two, or three copies of the NS gene when packaging an average of 12 influenza gene segments that include the 8 segments essential for infectivity.

Independent origin of IFN-alpha and IFN-beta in birds and mammals

Phylogenetic analysis of type I interferon (IFN) from birds and mammals strongly supported the hypothesis that the gene duplication giving rise to the alpha and beta families of mammalian IFN occurred after the divergence of birds from mammals, whereas the bird IFN that have been designated alpha and beta duplicated independently in the avian lineage. Therefore, IFN designated alpha and beta in birds are not orthologous to those similarly designated in mammals.

Turkey and chicken interleukin-2 cross-react in in vitro proliferation assays despite limited amino acid sequence identity

We cloned the cDNA of turkey interleukin-2 (IL-2), initially using oligonucleotide primers based on the sequence of the chicken IL-2 gene. Compared with the only other cytokines available for comparison, the interferons (IFN), the coding regions of the turkey and chicken IL-2 genes are much less conserved (86.24% nucleotide identical and 69.93% amino acid identical). The lack of nucleotide conservation was spread across the entire length of the coding region. In comparison, the promoters of the two avian IL-2 genes shared a high degree of identity (95.71% identical over 380 nucleotides). Phylogenetic analysis shows that turkey and chicken IL-2 have diverged to a greater extent than IL-2 from closely related mammalian species. Surprisingly, considering the low level of amino acid identity, including residues known to be important in binding the IL-2 receptor in mammalian species, both turkey and chicken IL-2 cross-react in functional assays.

Cytokine therapy: a natural alternative for disease control

Disease control in food production animals is normally mediated through the use of vaccines, chemicals and antibiotics. However, the extensive use of antibiotics and chemicals in livestock has resulted in environmental and human health concerns, particularly with regard to the emergence of drug-resistant bacteria in the food chain. In fact, the World Health Organisation (WHO) has now urged meat producers to use environmentally-friendly alternative methods to control disease. Cytokines, as natural mediators of the immune response, offer exciting alternatives to conventional therapeutics. The utilisation of cytokines is becoming more feasible with the recent cloning of a number of cytokine genes. Since the chicken's immune system is similar to that of mammals, they offer an attractive model system with which to study the effectiveness of cytokine therapy in the control of disease in intensive livestock. In this report we will review our recent studies on the therapeutic potential of chicken interferon gamma (ChIFN-gamma) as a vaccine adjuvant and a growth promoter.

Interferon induction in turkeys by oral administration of the imidazoquinolinamine S-28828 and modulation of the pathogenesis of Escherichia coli

A synthetic imidazoquinolinamine, S-28828, has been shown to be an effective antiviral and antitumor agent in mammals. This immune modifier induces a number of cytokines such as interferons, tumor necrosis factor-alpha, interleukins and granulocyte-macrophage colony-stimulating factors in mammals. We showed that when turkeys were given S-28828 orally, high serum titers of IFN were induced in a dose-dependent manner. Turkeys, once stimulated by S-28828, became refractory to IFN production by repeated stimulation. S-28828 induced spleen, bone marrow and peripheral leukocytes to produce IFN in vitro. Splenic adherent cells were the main producers of IFN after in vitro stimulation. S-28828-induced IFN was identified as type I IFN that was pH-resistant but heat-labile. We examined the effect of a high dose (100 mg kg(-1) body weight) of S-28828 on the pathogenesis of E. coli in turkeys. Treatment with S-28828 increased mortality in infected birds and impaired E. coli clearance from the liver. The enhancement of the pathogenicity of E. coli by S-28828 may have been due to the massive release of cytokines inducing a shock-like syndrome in infected turkeys.

Recombinant fowlpox viruses coexpressing chicken type I IFN and Newcastle disease virus HN and F genes: influence of IFN on protective efficacy and humoral responses of chickens following in ovo or post-hatch administration of recombinant viruses

We have constructed recombinant (r) fowl pox viruses (FPVs) coexpressing chicken type I interferon (IFN) and/or hemagglutinin-neuraminidase (HN) and fusion (F) proteins of Newcastle disease virus (NDV). We administered rFPVs and FPV into embryonated chicken eggs at 17 days of embryonation or in chickens after hatch. Administration of FPV or rFPVs did not influence hatchability and survival of hatched chicks. In ovo or after hatch vaccination of chickens with the recombinant viruses resulted in protection against challenge with virulent FPV and NDV. Chickens vaccinated with FPV or FPV-NDV recombinant had significantly lower body weight 2 weeks following vaccination. This loss in body weight was not detected in chickens receiving FPV-IFN and FPV-NDV-IFN recombinants. Chickens vaccinated with FPV coexpressing IFN and NDV genes produced less antibodies against NDV in comparison with chickens vaccinated with FPV expressing NDV genes.

Avian IFN-gamma genes: sequence analysis suggests probable cross-species reactivity among galliforms

Little is known about the evolution of cytokines in non-mammalian systems. To address this problem, we attempted to clone the gene for interferon-gamma (IFN-gamma) from a variety of avian species using oligonucleotide primers based on the sequence of the chicken IFN-gamma gene. The coding sequence and partial intron sequences were determined for four species, namely guinea fowl, ring-necked pheasant, Japanese quail, and turkey. To obtain sequence information on the gene extremities, a modified 5' and 3' RACE protocol was used. The sequence information showed that the coding regions of the IFN-gamma gene are highly conserved among the species studied (93.5%-96.7% and 87.8%-97.6% at the nucleotide and peptide levels, respectively) and are more conserved at the amino-terminal region (exons 1 and 2) than the carboxyl-terminal (exons 3 and 4). This high degree of overall identity at the predicted primary amino acid sequence level of the protein, including the deduced IFN-gamma receptor binding motifs, suggests that IFN-gamma may be cross-reactive among these species. Phylogenetic analysis shows that the similarity of the avian IFN-gamma sequences parallels the presumed evolutionary relationships between the species.

Avian macrophages: regulators of local and systemic immune responses

Macrophages are key regulatory cells of the immune system involved in initiating and directing the innate and specific immune responses, the systemic acute phase response, tissue repair, and tissue remodeling. In the early stages of a challenge from invading microorganisms or from tissue injury, macrophages defend local and systemic homeostasis by initiating a complex series of cellular, biochemical, and behavioral events. These pathophysiological adjustments are mediated by an extensive variety of communication molecules, including: cytokines, cytokine inhibitors, endocrine hormones, eicosanoids, neurotransmitters, and reactive oxygen intermediates. The cytokines produced by macrophages (monokines) are not well characterized relative to their mammalian counterparts, but a variety of chemokine, pro-inflammatory, and colony-stimulating factor activities have been described. Although the sequence homology, and thus species cross-reactivity, between avian and mammalian cytokines is typically low, the functional characteristics appear to be generally similar. The pro-inflammatory cytokines are important initiators and regulators of the local immune response. They are also released in sufficient quantities during some infections to coordinate a systemic acute phase response that impacts the growth, reproduction, and well-being of poultry. An understanding of the mechanisms and molecules used by macrophages to regulate immune and inflammatory responses may permit the development of products, diets, or husbandry techniques to modulate immunity for the enhancement of the productivity of poultry.

Oxygen radicals and nitric oxide production by turkey respiratory macrophages

The influence of different induction protocols on the recovery of elicited turkey respiratory macrophages (RM), and on their oxygenation activity and nitric oxide (NO) production was examined. RM were induced in three week old specific pathogen free turkeys with Sephadex G-50, Thioglycollate broth, and an emulsion of incomplete Freund's adjuvant (IFA), supplemented either with Mycoplasma hyorhinis grown in Modified Channock broth (IFA-M. hyorhinis) or with Modified Channock broth (IFA-Broth). The RM were recovered by lavage of the lungs and air sacs and were purified by centrifugation through a Percoll suspension. Their oxygenation activity was evaluated in luminol-enhanced chemiluminescence assays, following stimulation with Zymosan A. The NO production was evaluated by incubating the RM with lipopolysaccharide (LPS) from Salmonella enteritidis for 24 or 48 hours. The number of recovered RM was slightly, but not significantly lower for Sephadex G-50 and IFA-Broth than for Thioglycollate broth and IFA-M. hyorhinis. RM elicited with Sephadex G-50 and IFA-Broth showed a significantly higher oxidative burst response to Zymosan A, compared to the Thioglycollate and IFA-M. hyorhinis elicited RM. Although all elicited RM showed a high NO production upon stimulation with LPS, no significant differences were seen in the NO production of the RM obtained following the different induction treatments. Our results point out that care should be taken when applying elicited RM for in vitro assays, as distinct levels of oxygenation activity were obtained using different induction protocols.

Avian macrophage metabolism

This review considers the role of avian macrophages as a source of immune effector and immunoregulatory metabolites. Although considerable attention has been given to the importance of leukocytic cytokines, particularly the monokines such as interleukin-1 (IL-1), interleukin-6 (IL-6), tumor necrosis factor-alpha (TNF-alpha), and transforming growth factor-beta (TGF-beta), metabolites produced by macrophages appear to be of equal importance in determining the progression of immune responses. The three metabolite categories that have received the greatest attention are the reactive oxygen species (ROS), the reactive nitrogen intermediates (RNI), and the eicosanoids. Additionally, the xenobiotic metabolites produced via cytochrome P450 activity mediate some immune-environmental interactions. Each of these four metabolite categories is subject to different requirements for metabolite production, and each has distinct effector functions. An understanding of macrophage metabolite regulation could allow improvements in avian health management and production via the effective control of metabolite production. The present review considers prior and recent information on the production of the metabolites by avian macrophages. Additionally, the potential ramifications of metabolite production and regulation are discussed.

Structure of the chicken interferon-gamma gene, and comparison to mammalian homologues

The sequence of the chicken interferon-gamma (ifn-gamma) gene was determined, one of the first non-mammalian cytokine gene structures to be elucidated. Initial genomic clones were amplified from chicken genomic DNA and were used to isolate a cosmid clone covering the entire gene for sequencing. The exon:intron structure of chicken ifn-gamma is very similar to those of its mammalian homologues, with the exception of the third intron, which is markedly shorter in the chicken. The first exon contains both 5' UTR and signal sequence and the first 22 aa of the mature protein. The remainder of the coding region lies in exons 2-4. Exon 4 also encodes the stop codon and the 3' UTR, including two possible polyadenylation signals. A number of potential regulatory sequences similar to those found in mammals have been identified, in the promoter, in each intron and in the 3' UTR. In the promoter, these include the TATAATA- and CCAT-boxes, a consensus GATA motif in the reverse orientation and a potential NF-kappa B binding site. Other regulatory elements identified in the promoters of mammalian ifn-gamma genes are absent. Internal to the gene structure, regulatory sequences identified include elements found in the DNase I hypersensitivity region of the first intron of the human ifn-gamma gene and several potential NF-kappa B binding sites. The 3' UTR contains an AT-rich sequence, including nine repeats of the 'instability' motif ATTTA. As in mammals, chicken ifn-gamma is a single copy gene. The gene is highly conserved, with no polymorphisms yet identified using either RFLP or SSCP in the coding region. However, promoter sequence polymorphisms between different inbred lines of chickens have been identified, with possible links to disease resistance.

Expression and functional characterization of recombinant chicken interferon-gamma

A cDNA encoding chicken interferon-gamma (chIFN-gamma) was cloned from a CD4+ T-cell hybridoma by reverse transcription-polymerase chain reaction (RT-PCR) and expressed in Escherichia coli, COS- and CEC-32 fibroblast cell lines. In general, recombinant chicken IFN-gamma (rchIFN-gamma) expressed in the COS- and CEC-32 cell lines showed high bioactivity in vitro. The kinetics of IFN-gamma gene expression were examined in concanavalin A (Con A)-activated spleen lymphocytes by Northern blot and RT-PCR. IFN-gamma mRNA was detected as early as 30 min after Con A activation, reached peak expression at 2 h and then decreased starting at 4 h post Con A activation. A rabbit serum made to a synthetic peptide of IFN-gamma immunoprecipitated a 60 kDa E. coli maltose-binding fusion protein of recombinant IFN-gamma (MBP-IFN) and a 26-27 kDa secreted protein from COS cells and Con A-activated spleen cells. IFN-gamma inhibited vesicular stomatitis virus (VSV) mediated cytotoxicity of chicken embryonic fibroblast (CEF) cells and upregulated the expression of many macrophage cell surface antigens, including class I and class II major histocompatibility complex (MHC) proteins. These results show that chicken IFN-gamma possesses anti-viral activity and immunoregulates macrophage activities.

In vivo and In vitro interferon induction in chickens by S -28828, an imidazoquinolinamine immunoenhancer

Imiquimod and its analogs belonging to a class of imidazoquinolinamines, activate immune system via cytokine induction, and have antitumor and antiviral effects in mammals. In this study, we showed that a related analog, designated S-28828, induced interferon (IFN) and macrophage activating cytokine(s) (macrophage activating factor, MAF) in chickens in vivo, ex vivo, and in vitro. IFN and MAF were detectable in the serum of chickens following oral administration. Serum IFN levels were the highest at 2 h after treatment. Although there was no detectable IFN in sera of chickens at 8, 24, and 48 h after treatment, high levels of interferon inducible enzyme, 2'-5' oligoadenylate synthase (2'5'OAS) were present at these time points. In vitro and ex vivo studies showed that spleen cells, bone marrow (BM) cells, and peripheral blood leukocytes (PBL) were capable of producing IFN and MAF, although spleen cells produced the highest levels. Our results suggest that S-28828 administered orally may be a useful immunoenhancing and antiviral agent for chickens.