Molecular cloning, expression and characterization of Pekin duck interferon-λ

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.

Pattern Recognition Receptor Signaling and Innate Responses to Influenza A Viruses in the Mallard Duck, Compared to Humans and Chickens

Mallard ducks are a natural host and reservoir of avian Influenza A viruses. While most influenza strains can replicate in mallards, the virus typically does not cause substantial disease in this host. Mallards are often resistant to disease caused by highly pathogenic avian influenza viruses, while the same strains can cause severe infection in humans, chickens, and even other species of ducks, resulting in systemic spread of the virus and even death. The differences in influenza detection and antiviral effectors responsible for limiting damage in the mallards are largely unknown. Domestic mallards have an early and robust innate response to infection that seems to limit replication and clear highly pathogenic strains. The regulation and timing of the response to influenza also seems to circumvent damage done by a prolonged or dysregulated immune response. Rapid initiation of innate immune responses depends on viral recognition by pattern recognition receptors (PRRs) expressed in tissues where the virus replicates. RIG-like receptors (RLRs), Toll-like receptors (TLRs), and Nod-like receptors (NLRs) are all important influenza sensors in mammals during infection. Ducks utilize many of the same PRRs to detect influenza, namely RIG-I, TLR7, and TLR3 and their downstream adaptors. Ducks also express many of the same signal transduction proteins including TBK1, TRIF, and TRAF3. Some antiviral effectors expressed downstream of these signaling pathways inhibit influenza replication in ducks. In this review, we summarize the recent advances in our understanding of influenza recognition and response through duck PRRs and their adaptors. We compare basal tissue expression and regulation of these signaling components in birds, to better understand what contributes to influenza resistance in the duck.

The role of respiratory epithelium in host defence against influenza virus infection

The respiratory epithelium is the major interface between the environment and the host. Sophisticated barrier, sensing, anti-microbial and immune regulatory mechanisms have evolved to help maintain homeostasis and to defend the lung against foreign substances and pathogens. During influenza virus infection, these specialised structural cells and populations of resident immune cells come together to mount the first response to the virus, one which would play a significant role in the immediate and long term outcome of the infection. In this review, we focus on the immune defence machinery of the respiratory epithelium and briefly explore how it repairs and regenerates after infection.

Molecular identification of goose (Anser cygnoide) suppressor ubiquitin-specific protease 18 (USP18) and the effects of goose IFN and TMUV on its comparative transcripts

Ubiquitin-specific protease 18 (USP18) is known as an inhibition factor and has been associated with the innate immune response to pathogens. USP18 is the only deconjugating protease with specificity for interferon-stimulated gene 15 (ISG15), which is supposed to be missing in birds. To analyze the efficacy of goose USP18 (goUSP18) against Tembusu virus (TMUV) infection, we first cloned USP18 homologous cDNA from TMUV infected geese. The coding sequence was 1131 bp, and the deduced amino acid sequence shared conserved motifs with its homologues. Tissue-specific expression has shown that goUSP18 transcripts are strongly expressed in the spleen and liver of adult geese, as well as in the pancreas of goslings. Moreover, the goUSP18 transcripts were induced by goose interferons (goIFN) in goose embryo fibroblasts (GEF) and by TLR ligands in peripheral blood mononuclear cells (PBMC). Notably, goUSP18 transcripts were highly up-regulated by TMUV infection compared to the basal level in uninfected birds. Taken together, these results suggested that goUSP18 was involved in host innate immunity against TMUV infection.

HTNV-induced upregulation of miR-146a in HUVECs promotes viral infection by modulating pro-inflammatory cytokine release

Increasing research has shown a link between viruses and miRNAs, such as miRNA-146a, in regulating virus infection and replication. In the current study, the association between miR-146a and hantaan virus (HTNV) infection in human umbilical vein endothelial cells (HUVECs) was investigated, with a focus on examining the expression of pro-inflammatory cytokines. The results showed that HTNV infection promoted the production of miR-146a in HUVECs and activated nuclear factor-κB (NF-κB) signaling, along with the upregulation of pro-inflammatory cytokines, including interleukin 8 (IL-8), C-C Motif Chemokine Ligand 5 (CCL5, also RANTES), interferon-inducible protein-10 (IP-10) and interferon beta (IFN-β). Moreover, miR-146a exhibited a negative regulatory effect on the NF-κB pathway. Accordingly, a miR-146a inhibitor increased the expression of IL-8, CCL5, IP-10 and IFN-β, whereas a miR-146a mimic reduced the levels of these cytokines. Consequently, exogenous transduction of miR-146a significantly enhanced HTNV replication in HUVEC cells. We also discovered that viral proteins (NP/GP) contributed to miR-146a expression via enhancement the activity of miR-146a promoter. In conclusion, these results imply the negative regulation of miR-146a on the production of HTNV-induced pro-inflammatory cytokines contributes to virus replication, which suggest that miR-146a may be regarded as a novel therapeutic target for HTNV infection.

Cross-species antiviral activity of goose interferon lambda against duck plague virus is related to its positive self-regulatory feedback loop

Duck plague virus (DPV) is a virus of the Herpesviridae family that leads to acute disease with a high mortality rate in ducks. Control of the disease contributes to the development of poultry breeding. Type III IFN family (IFN-λs) is a novel member of the IFN family, and goose IFN-λ (goIFN-λ) is a newly identified gene whose antiviral function has only been investigated to a limited extent. Here, the cross-species antiviral activity of goIFN-λ against DPV in duck embryo fibroblasts (DEFs) was studied. We found that pre-treatment with goIFN-λ greatly increased the expression of IFN-λ in both heterologous DEFs and homologous goose embryo fibroblasts (GEFs), while differentially inducing IFNα- and IFN-stimulated genes. Additionally, a positive self-regulatory feedback loop of goIFN-λ was blocked by a mouse anti-goIFN-λ polyclonal antibody, which was confirmed in both homologous GEFs and goose peripheral blood mononuclear cells (PBMCs). The suppression of the BAC-DPV-EGFP by goIFN-λ in DEFs was confirmed by fluorescence microscopy, flow cytometry (FCM) analysis, viral copies and titre detection, which can be rescued by mouse anti-goIFN-λ polyclonal antibody incubation. Finally, reporter gene assays indicated that the cross-species antiviral activity of goIFN-λ against BAC-DPV-EGFP is related to its positive self-regulatory feedback loop and subsequent ISG induction. Our data shed light on the fundamental mechanisms of goIFN-λ antiviral function in vitro and extend the considerable range of therapeutic applications in multiple-poultry disease.

The Superiority of IFN-λ as a Therapeutic Candidate to Control Acute Influenza Viral Lung Infection

Here, we studied the IFN-regulated innate immune response against influenza A virus (IAV) infection in the mouse lung and the therapeutic effect of IFN-λ2/3 in acute IAV lung infection. For viral infections, IAV (WS/33, H1N1, PR8 H1N1, H5N1) were inoculated into wild-type mice by intranasal delivery, and IAV mRNA level and viral titer were measured. To compare the antiviral effect of IFNs in vivo in the lung, neutralizing antibodies and recombinant IFNs were used. After intranasal inoculation of IAV into mice, viral infection peaked at 7 days postinfection, and the IAV titer also reached its peak at this time. We found that IFN-β and IFN-λ2/3 were preferentially induced after IAV infection and the IFN-λ2/3-mediated innate immune response was specifically required for the induction of IFN-stimulated genes (ISGs) transcription in the mouse respiratory tract. Neutralization of secreted IFN-λ2/3 aggravated acute IAV lung infection in mice with intact IFN-β induction; consistent with this finding, the transcription of ISGs was significantly reduced. Intranasal administration of IFN-λ2/3 significantly suppressed various strains of IAV infection, including WS/33 (H1N1), PR (H1N1), and H5N1 in the mouse lung, and was accompanied by greater up-regulation of ISGs. Taken together, our data indicate that the IFN-λ2/3-mediated innate immune response is necessary to protect the lungs from IAV infection, and intranasally delivered IFN-λ2/3 has the potential to be a useful therapeutic strategy for treating acute IAV lung infection.

Identification of Type III Interferon (IFN-λ) in Chinese Goose: Gene Structure, Age-Dependent Expression Profile, and Antiviral Immune Characteristics In Vivo and In Vitro

Type III interferons (IFN-λ1/λ2/λ3, also known as IL-29/28A/28B, and IFN-λ4) are a recently discovered interferon group. In this study, we first identified the Chinese goose IFN-λ (goIFN-λ). The full-length sequence of goIFN-λ was found to be 823 bp. There was only one open reading frame that contained 570 bp, and, encoded 189 amino acids. The predicted goIFN-λ protein showed 78%, 67%, and 40% amino acid identity with duIFN-λ, chIFN-λ, and hIFN-λ3, respectively. The tissue distribution of goIFN-λ existed as a parallel distribution with goIFNLR1 as its functional receptor, which was mainly expressed in epithelium-rich tissues, such as lung, gizzard, proventriculus, skin and pancreas, and immune tissues, such as harderian gland and thymus. Furthermore, the immunological characteristics studies of goIFN-λ showed that there was a significant increase in the mRNA at the transcriptional level of goIFN-λ after the peripheral blood mononuclear cells were stimulated with ploy (I:C) and ODN2006, and infected with Gosling plague virus (GPV). In vivo, the mRNA transcriptional level of goIFN-λ increased nearly 20 times in the lung tissue and nearly 40 times in the pancreatic tissue after being artificially infected with H9N2 AIV. It is suggested that goIFN-λ might play a pivotal role in the mucosal immune protection and antiviral defense.

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.

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.