Cloning and Characterization of Porcine Interferon-δ-Related Genes Identified by Genomic Database Screening

Transcriptomic and antiviral analyses of PoIFN-Delta5 against porcine enteric viruses in porcine intestinal epithelial cells

The interferon-delta family was first reported in domestic pigs and belongs to the type I interferon (IFN-I) family. The enteric viruses could cause diarrhea in newborn piglets with high morbidity and mortality. We researched the function of the porcine IFN-delta (PoIFN-δ) family in the porcine intestinal epithelial cells (IPEC-J2) cells infected with porcine epidemic diarrhea virus (PEDV). Our study found that all PoIFN-δs shared a typical IFN-I signature and could be divided into five branches in the phylogenic tree. Different strains of PEDV could induce typical IFN transitorily, and the virulent strain AH2012/12 had the strongest induction of porcine IFN-δ and IFN-alpha (PoIFN-α) in the early stage of infection. In addition, it was found that PoIFN-δ5/6/9/11 and PoIFN-δ1/2 were highly expressed in the intestine. PoIFN-δ5 had a better antiviral effect on PEDV compared to PoIFN-δ1 due to its higher induction of ISGs. PoIFN-δ1 and PoIFN-δ5 also activated JAK-STAT and IRS signaling. For other enteric viruses, transmissible gastroenteritis virus (TGEV), porcine deltacoronavirus (PDCoV), and porcine rotavirus (PoRV), PoIFN-δ1 and PoIFN-δ5 both showed an excellent antiviral effect. Transcriptome analyses uncovered the differences in host responses to PoIFN-α and PoIFN-δ5 and revealed thousands of differentially expressed genes were mainly enriched in the inflammatory response, antigen processing and presentation, and other immune-related pathways. PoIFN-δ5 would be a potential antiviral drug, especially against porcine enteric viruses. These studies were the first to report the antiviral function against porcine enteric viruses and broaden the new acquaintances of this type of interferon though not novelly discovered.

Novel type-I interferons from the dromedary camel: Molecular identification, prokaryotic expression and functional characterization of camelid interferon-delta

The last two decades have seen the emergence of three highly pathogenic coronaviruses with zoonotic origins, which prompted immediate attention to the underlying cause and prevention of future outbreaks. Intensification of camel husbandry in the Middle East has resulted in increased human-camel interactions, which has led to the spread of potentially zoonotic viruses with human spillover risks like MERS-coronavirus, camelpox virus, etc. Type-I interferons function as the first line of defense against invading viruses and are pivotal for limiting viral replication and immune-mediated pathologies. Seven novel dromedary camel interferon delta genes were identified and cloned. Functional characterization of this novel class of IFNs from the mammalian suborder tylopoda is reported for the first time. The camel interferon-delta proteins resemble the reported mammalian counterparts in sequence similarity, conservation of cysteines, and phylogenetic proximity. Prokaryotically expressed recombinant camel interferon-δ1 induced IFN-stimulated gene expression and also exerted antiviral action against camelpox virus, an endemic zoonotic virus. The pre-treatment of camel kidney cells with recombinant camel IFN-δ1 increased cell survival and reduced camelpox virus in a dose-dependent manner. The identification of novel IFNs from species with zoonotic spillover risk such as camels, and evaluating their antiviral effects in-vitro will play a key role in improving immunotherapies against viruses and expanding the arsenal to combat emerging zoonotic pathogens.

Antiviral activity of porcine interferon delta 8 against pesudorabies virus in vitro

Recently, pseudorabies virus (PRV) was isolated from human cases, and infected patients presented with respiratory dysfunction and acute neurological symptoms. However, there was no available effective drug to prevent the progression of PRV infection. In the present study, we screened a stably Drosophila S2 cell line which can secretory express a novel type I IFNs-interferon delta 8 (IFN-δ8) and the yield was about 10 mg/L. After purification, recombinant IFN-δ8 was demonstrated to be acid-stable, heat-stable, and nontoxic to PK-15 and 3D4/21 cells. Antiviral effects of IFN-δ8 against PRV were tested in vitro. Our results showed both pre- and post-treatment, recombinant PoIFN-δ8 exerted a significant protective effect against PRV infection in PK-15 and 3D4/21 cells. In addition, PoIFN-δ8 remarkably increased the expression of eight IFN-stimulated genes (ISGs), including ISG15, OAS1, PKR, MX1, CH25H, IFITM1, IFITM2 and IFITM3, to resist virus infection. These findings highlight the significance of IFN-δ8 that might serve as an antiviral agent for the prevention of PRV infection, and maybe expand the potential function of IFN antiviral drugs in the future.

Antiviral activity of porcine interferon delta 8 against foot-and-mouth disease virus in vitro

Foot-and-mouth disease (FMD) is one of the most devastating diseases affecting livestock. Since vaccines fail to provide protection until seven days post-vaccination, the application of anti-viral molecules is imperative for suppressing the spread of FMDV prior to development of an adaptive immune response. Interferons (IFNs) are effective for the host to fight FMDV infections; however, a novel type I IFNs, interferon delta (IFN-δ), has not been investigated for their antiviral effects against this virus. Thus, this study investigated FMDV infection, upon pre- and post-treatment with PoIFN-δ8. Real-time quantitative PCR was used to quantify the expression levels of IFN-stimulated genes (ISGs), including ISG15, OAS1, PKR, and Mx1. Results showed the PoIFN-δ8 lacking its signal sequence was efficiently expressed in Escherichia coli, and the purified recombinant PoIFN-δ8 exerted a significantly protective effect against two different serotypes of FMDV in IBRS-2 cells. In addition, PoIFN-δ8 induced the expression of IFN-stimulated genes. These findings highlight the significance of PoIFN-δ might serve as an antiviral agent for the prevention of FMDV in pigs and will stimulate the study of exploiting the potential biological functions of IFN-δ in the future.

Functional characterization of canine interferon-lambda

In this study, we provide the first comprehensive annotation of canine interferon-λ (CaIFN-λ, type III IFN). Phylogenetic analysis based on genomic sequences indicated that CaIFN-λ is located in the same branch with Swine IFN-λ1 (SwIFN-λ), Bat IFN-λ1 (BaIFN-λ), and human IFN-λ1 (HuIFN-λ1). CaIFN-λ was cloned, expressed in Escherichia coli, and purified to further investigate the biological activity in vitro. The recombinant CaIFN-λ (rCaIFN-λ) displayed potent antiviral activity on both homologous and heterologous animal cells in terms of inhibiting the replication of the New Jersey serotype of vesicular stomatitis virus (VSV), canine parvovirus, and influenza virus A/WSN/33 (H1N1), respectively. In addition, we also found that rCaIFN-λ exhibits a significant antiproliferative response against A72 canine tumor cells and MDCK cells in a dose-dependent manner. Furthermore, CaIFN-λ activated the JAK-STAT signaling pathway. To evaluate the expression of CaIFN-λ induced by virus and the expression of IFN-stimulated genes (ISGs) induced by rCaIFN-λ in the MDCK cells, we measured the relative mRNA level of CaIFN-λ and ISGs (ISG15, Mx1, and 2'5'-OAS) by quantitative real-time PCR and found that the mRNA level of CaIFN-λ and the ISGs significantly increased after treating the MDCK cells with viruses and rCaIFN-λ protein, respectively. Finally, to evaluate the binding activity of rCaIFN-λ to its receptor, we expressed the extracellular domain of the canine IFN-λ receptor 1 (CaIFN-λR1-EC) and determined the binding activity via ELISA. Our results demonstrated that rCaIFN-λ bound tightly to recombinant CaIFN-λR1-EC (rCaIFN-λR1-EC).

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.

Human cytokines activate JAK-STAT signaling pathway in porcine ocular tissue

Background

The JAK/STAT (Janus Tyrosine Kinase, Signal Transducers and Activators of Transcription) pathway is associated with cytokine or growth factor receptors and it is critical for growth control, developmental regulation and homeostasis. The use of porcine ocular cells as putative xenotransplants appears theoretically possible. The aim of this study was to investigate the response of various porcine ocular cells in vitro to human cytokines in regard to the activation of JAK-STAT signaling pathways.

Methods

Porcine lens epithelial cells, pigmented iris epithelial cells and pigmented ciliary body cells were used in this study. These cells were isolated from freshly enucleated porcine eyes by enzymatic digestion. Cultured cells between passages 3–8 were used in all experiments. Electromobility shift assay (EMSA), proliferation assay, immunofluorescence staining and flow cytometry were used to evaluate the JAK-STAT signaling pathway in these cells.

Results

JAK/STAT signaling pathways could be activated in porcine pigmented epithelial ciliary body cells, in pigmented iris epithelial cells and in lens epithelial cells in response to porcine and human interferons and cytokines. All cells showed very strong STAT1 activation upon stimulation with porcine interferon-gamma. Porcine ocular cells also respond to human cytokines; IFN-alpha induced strong activation of STAT1 in EMSA, flow cytometry and immunofluorescence experiments whereas activation of STAT3 was less strong in EMSA, but strong in flow cytometry and immunofluorescence. Human recombinant IL-6 activated STAT3 and human IL-4 activated STAT6. With the help of immunofluorescence assay and flow cytometry we observed nuclear localization of STAT proteins after activation of porcine ocular cells with cytokines and interferons. Human IFN-α had an inhibitory effect on porcine ocular cells in proliferation assays.

Conclusion

Our study demonstrated that some types of human cytokines and interferon activate intracellular JAK-STAT signaling pathways in porcine ocular cells. We hypothesize that direct stimulation of the JAK-STAT pathway in porcine cells in response to human cytokines will lead to complications or failure, if pig-to-human ocular tissue xenotransplantation were to be carried out. For successful xenotransplantation among other obstacles there must be new approaches developed to regulate signaling pathways.

Molecular and functional characterization of canine interferon-epsilon

In this study, we provide the first comprehensive annotation of the entire family of canine interferons (IFNs). Canine IFN-ε (IFNE), IFN-κ (IFNK), and IFN-λ (IFNL) were discovered for the first time. Ten functional and 2 truncated IFN-α (IFNA) pseudogenes were found in the genome, which also enriched the existing knowledge about canine IFNA. The canine type I IFN genes are clustered on chromosome 11, and their relative arrangements are illustrated. To further investigate the biological activity of canine IFNE, it was expressed and purified in Escherichia coli. Recombinant canine IFNE (rCaIFN-ε) displayed potent antiviral activity on both homologous and heterologous animal cells in vitro, indicating that rCaIFN-ε has more broad cross-species activity than recombinant canine IFNA (rCaIFN-α). The antiviral activities of rCaIFN-ε and rCaIFN-α7 against different viruses on MDCK cells were also evaluated. The antiviral activities of recombinant canine IFNK and IFNL were demonstrated using a VSV-MDCK virus-target cell system. rCaIFN-ε exhibited a significant anti-proliferative response against A72 canine tumor cells and MDCK canine epithelial cells in a dose-dependent manner. rCaIFN-α7 was approximately 16-fold more potent than rCaIFN-ε in promoting natural killer cell cytotoxicity activity. Further, rCaIFN-ε can activate the JAK-STAT signaling pathway.