Characterization and signaling pathway analysis of interferon-kappa in bovine

Blocking virus infection with BacMam virus delivery bovine interferon-α gene

Interferon-αs (IFN-αs) are crucial cytokines for inducing protective antiviral responses. The baculovirus-mediated gene transduction of mammalian cells (BacMam) is an efficient delivery tool for recombinant protein expression in mammalian cells. This study focuses on the delivery of bovine IFN-α (BoIFNα) using the BacMam system. A recombinant pACEMam1-BoIFNα bacmid was constructed, and a recombinant BacMam-BoIFNα virus was obtained. After transducing HEK293T cells with this virus, BoIFNα protein was successfully secreted into the cell supernatant, displaying antiviral activities against VSV, BPIV3, BEV, and BVDV in bovine-derived cells. Additionally, the BacMam-BoIFNα virus inhibited the replication of these viruses in MDBK cells, induced the transcription of ISGs, and the expression of M × 1 in both MDBK and BT cells. These induction effects were significantly reduced following treatment with a JAK1 inhibitor, suggesting that the BacMam-BoIFNα virus exerts antiviral activity in MDBK cells through JAK-STAT signaling pathway. Furthermore, the study found that the BacMam-BoIFNα virus significantly inhibited the replication of BPIV3 in the lung and trachea of mice. Overall, this study demonstrates that the BacMam-BoIFNα virus have antivirus activities both in vitro and in vivo, signaling through JAK-STAT pathway, and provides an efficient interferon gene delivery tool for combating bovine viral infections.

Biological Activity of Optimized Codon Bovine Type III Interferon Expressed in Pichia pastoris

Type III interferons (IFN-λs) exhibit potent antiviral activity and immunomodulatory effects in specific cells. Nucleotide fragments of the bovine ifn-λ (boifn-λ) gene were synthetized after codon optimization. The boifn-λ gene was then amplified by splicing using overlap extension PCR (SOE PCR), resulting in the serendipitous acquisition of the mutated boIFN-λ3^V18M. The recombinant plasmid pPICZαA-boIFN-λ3/λ3^V18M was constructed, and the corresponding proteins were expressed in Pichia pastoris with a high-level extracellular soluble form. Dominant expression strains of boIFN-λ3/λ3^V18M were selected by Western blot and ELISA and cultured on a large scale, and the recombinant proteins purified by ammonium sulfate precipitation and ion exchange chromatography yielded 1.5g/L and 0.3 g/L, with 85% and 92% purity, respectively. The antiviral activity of boIFN-λ3/λ3^V18M exceeded 10⁶ U/mg, and they were neutralized with IFN-λ3 polyclonal antibodies, were susceptible to trypsin, and retained stability within defined pH and temperature ranges. Furthermore, boIFN-λ3/λ3^V18M exerted antiproliferative effects on MDBK cells without cytotoxicity at 10⁴ U/mL. Overall, boIFN-λ3 and boIFN-λ3^V18M did not differ substantially in biological activity, except for reduced glycosylation of the latter. The development of boIFN-λ3 and comparative evaluation with the mutant provide theoretical insights into the antiviral mechanisms of boIFN-λs and provide material for therapeutic development.

Bovine cyclic GMP-AMP synthase recognizes exogenous double-stranded DNA and activates the STING-depended interferon β production pathway

The cytosolic DNA sensor cyclic GMP-AMP synthase (cGAS) recognizes exogenous double-stranded DNA and produces 2'3'-cyclic GMP-AMP (2'3'-cGAMP), activating the stimulator of interferon genes (STING) and innate immunity. Bovine cGAS functions remain poorly understood. Herein, the coding sequence of the bo-cGAS gene was obtained and its recognition function was investigated. Bo-cGAS consists of 1542 nucleotides and the encoding acid sequence contained high sequence homology to that of other livestock. Bo-cGAS was localized in the endoplasmic reticulum and was abundant in the lung. Bo-cGAS and bo-STING coexistence significantly activated the IFN-β promotor. Synthesized 2'3'-cGAMP activated the STING-dependent pathway. Upon bo-cGAS recognition of poly(dA:dT) and bovine herpesvirus type 1 (BHV-1), Viperin transcription displayed the opposite time-dependent trend. Significant restriction of IFN-β transcription but augmentation of myxovirus resistance protein 1 (Mx1) and Viperin occurred during BHV-1 infection. Thus, bo-cGAS recognized exogenous double-stranded DNA and triggered the STING-dependent IFN-β production pathway.

A Novel Type-I Interferon Family, Bovine Interferon-Chi, Is Involved in Positive-Feedback Regulation of Interferon Production

Interferon-chi (IFN-χ) is a type of function-unknown IFN. IFN-χ in bovines (BoIFN-χ) has evolved as a multigene family. This family comprises four IFN-χ subtypes, two of which are functional genes, which we demonstrated to (i) have antiviral and antiproliferative activities, (ii) be highly sensitive to trypsin, and (iii) remain stable with changes in pH and temperature. BoIFN-χ is a key intermediate in antiviral response, PAbs against BoIFN-χs could downregulate the transcriptional activation of ISGs induced by poly(I:C), and BoIFN-χs could be induced upon virus infection at the early and late phase. Additionally, BoIFN-χs bind with type-I IFN receptors, induce transcription of interferon regulatory factor 7 (IRF7), interferon-stimulated genes (ISGs), and type-I IFNs as well as myxovirus resistance protein 1 (Mx1) expression. Expression of ISGs and activation of IFN-stimulated response element (ISRE) induced with BoIFN-χs could be downregulated significantly by the Janus kinase (JAK) 1 and signal transducers and activators of transcription (STAT) 1 inhibitor. The promoters of BoIFN-β, nuclear factor-kappa B, and ISRE could be activated with BoIFN-χs, and the BoIFN-χ promoter could be activated by other type-I IFNs. Overall, BoIFN-χ could be induced with virus infection and signal through the JAK-STAT pathway to form a positive-feedback regulation of IFN production. These findings may facilitate further research on the role of IFN-χ in innate immune responses.

Molecular and functional characterization of ovis aries IFN-epsilon

Interferon-epsilon (IFN-ε) is a type I IFN playing an essential role in innate and adaptive immunity against viral infection. Ovis aries IFN-ε (OvIFN-ε), consisting of 582 bp and which encodes a protein of 193 amino acids containing a signal peptide of 21 amino acids, was cloned and characterized. OvIFN-ε shares 51.6∼ 86.5% similarity to other species of IFN-ε, and evolves from the IFN-ε branch but not the other types of IFN. Additionally, OvIFN-ε gene is well conserved during evolution, and is highly transcribed in the liver, lung, brain, skin, ovary and uterus. Recombinant protein of OvIFN-ε was expressed in Escherichia coli and purified with nickel chelated column, which exhibited broad antiviral activity in vitro, sensitivity of trypsin, and stability of pH and temperature to some extent. Furthermore, OvIFN-ε could induce the transcription of ISG15, Mx1 and OAS in a time-dependent manner, as well as inhibit the VSV and BVDV replication in Ovis aries peripheral blood lymphocyte cells and MDBK cells. This study revealed OvIFN-ε has the typical characterization of type I IFNs and exerts antiviral activity against VSV and BVDV, and induces the expression of ISGs, which not only enriches the understanding of IFN-ε, but also facilitates further research on the antiviral defense responses of Ovis aries.

Molecular cloning and transcriptional regulation of Indian peafowl (Pavo cristatus) IFN-α gene

Interferon-α (IFN-α) resists viral infections by triggering the transcription of a diverse range of antiviral IFN-stimulated genes (ISGs). However, information about the Indian peafowl (Pavo cristatus) IFN-α (PcIFN-α) has not been reported. In this study, a PcIFN-α gene was amplified, which encoded a protein of 193 amino acids with a 26-amino acid signal peptide sharing 72.16-95.70% identity with other avians in Aves. After expression in prokaryote, PcIFN-α was analyzed for its physicochemical property and antiviral activity. Intriguingly, compared with chicken IFN-α, an effective viral infection therapeutic agent, PcIFN-α showed superior anti-VSV, NDV, and AIV activities, which were then abrogated by rabbit anti-PcIFN-α antibodies in vitro. Moreover, PcIFN-α was shown to be highly sensitive to trypsin; however, it remained stable despite changes in pH and temperature. Additionally, PcIFN-α induced the transcriptional or translational levels of Mx1 and ISG12 genes time-dependently. Overall, the present study revealed that PcIFN-α is a potential novel effective therapeutic agent in antiviral defense responses in peafowl, improving understanding of its involvement in bird antiviral defense.

Characterization, functional and signaling elucidation of pigeon (Columba livia) interferon-α: Knockdown p53 negatively modulates antiviral response

The regulation of interferon-α signaling pathways is essential to protect the host from infection with a broad range of viruses. However, information regarding antiviral response and the specific molecular mechanism of Columba livia interferon-α (CoIFN-α) has not been reported to date. In this study, we cloned a 723bp complete ORF of CoIFN-α gene. The specific antiviral activity of CoIFN-α in VSV (TCID₅₀ = 10^-5.87/100 μL)-infected CEFs reached 5.5 × 10⁵ U/mg. Moreover, our result indicated that the anti-VSV efficient of CoIFN-α might depend on the expression of NF-κB. CoIFN-α also showed high sensitivity to trypsin and relatively stable after acid, alkali or heat treatment. Moreover, CoIFN-α activated STAT/Jak signaling and autophagy to inhibit VSV-induced apoptosis. Although the expression of p53 was further increased, apoptosis was not involved in CoIFN-α against VSV. Notably, although STAT signaling was efficiently activated, knockdown p53 did inhibit the antiviral activity of the CoIFN-α via decreasing the expression of Mx1 but not weakened Jak phosphorylation. Moreover, VSV aggravated the apoptosis and the expression of cleaved Mdm2 in knockdown p53 under preincubated CoIFN-α. Taken together, p53 might as a highly interconnected regulator in IFN-α antiviral response and cleaved Mdm2 might as a dominant-negative regulator by competing with full length Mdm2 for p53 binding in virus infection. Overall, our research not only enriches CoIFN-α antiviral features but also helps explain that p53 enhance the CoIFN-α antiviral response against pigeon viral diseases.

Design, biological activity and signaling pathway of bovine consensus omega interferon expressed in Pichia pastoris

The bovine IFN-ω (BoIFN-ω) multigene family is located on chromosome 8, which has 14 potential functional genes and 10 pseudogenes. After aligning 14 BoIFN-ω subtypes and assigning the most frequently occurring amino acids in each position, one artificial consensus BoIFN-ω (CoBoIFN-ω) gene was designed, optimized and synthesized. Then, CoBoIFN-ω was expressed in Pichia pastoris, which was demonstrated to have 3.94-fold and 14.3-fold higher antiviral activity against VSV on MDBK cells than that of BoIFN-ω24 and BoIFN-ω3, respectively. Besides this, CoBoIFN-ω was confirmed to have antiviral activity against VSV on BL, BT, PK-15 cells, and against BEV, BHV-1, BPIV3 on MDBK cells. Additionally, CoBoIFN-ω could bind with bovine type I IFN receptors, and then activate the promoters of NF-κB, ISRE and BoIFN-β, and induce the transcription of ISGs and expression of Mx1 and NF-κB p65, which suggested CoBoIFN-ω exerts antiviral activity via activation of the JAK-STAT signaling pathway. Overall, this research on CoBoIFN-ω not only extends and improves consensus IFN research, but also reveals that CoBoIFN-ω has the potential to be used in the therapy of bovine viral diseases.

Evolutional conservation of molecular structure and antiviral function of a type I interferon, IFN-kappa, in poultry

IFN-kappa (IFN-κ) is a type I IFN expressed by keratinocytes, monocytes and dendritic cells with important roles during the innate immune response period. This research was conducted to elaborate the evolution and characteristics of IFN-κ in poultry. Chicken IFN-κ is located on the sex-determining Z chromosome, which is greatly different from mammals. Poultry IFN-κ cluster together in a species-specific manner through positive selection pressure and share only 19-33% homology with mammalian IFN-κ and poultry other type I IFN. Both chicken and duck IFN-κ was constitutively expressed in spleen, skin, lung, and peripheral blood mononuclear cells (PBMC), as well as being significantly induced after treatment with virus in PBMC. Biologically, poultry IFN-κ has antiviral activity against VSV in chicken embryonic fibroblasts and duck embryonic fibroblasts (CEF and DEF) cells, and induces the expression of IFN stimulated genes (ISGs). After treatment with JAK1 inhibitor, the ISGs expression can be down-regulated. Overall, our research on poultry IFN-κ not only enriches the knowledge about IFN-κ but also facilitates further research on the role of type I IFNs in antiviral defense responses in poultry.

Identification and characterization of a rabbit novel IFN-α unlocated in genome

The multigene family of rabbit IFN-α (RbIFN-α) is located on chromosome 1, which shows seven functional genes in type I IFN locus. A novel RbIFN-α that remains unlocated in the rabbit genome was amplified and designated as the first novel rabbit IFN-α (RbIFN-αNov1), which possesses the typical molecular characteristics of type I IFNs and could be induced in RK-13 cells and peripheral blood mononuclear cells. After the mature peptide of RbIFN-αNov1 was expressed, its antiviral activity, physicochemical characteristics, and cytotoxicity were determined in vitro. Results indicated that RbIFN-αNov1 exerted a high specific antiviral activity against VSV and a low cytotoxic effect on RK-13 cells. RbIFN-αNov1 showed high sensitivity to trypsin and remained relatively stable after acid, alkali, or heat treatment. RbIFN-αNov1 could induce Mx1 expression on RK-13 cells and activate the NF-κB, ISRE and BoIFN-β promoter activities on bovine testicular cells. Overall, our research on RbIFN-αNov1 not only enriches the knowledge about rabbit IFNs but also makes RbIFN-αNov1 have the potential to be used as an effective therapeutic agent for rabbit viral diseases.

Chicken IFN Kappa: A Novel Cytokine with Antiviral Activities

Interferons (IFNs) are essential components of the host innate immune system and define first-line of defence against pathogens. In mammals, several type I IFNs are identified, however, only limited data is available on the repertoire of IFNs in avian species. Here we report the characterization of chicken IFN-κ (chIFN-κ) near the type I IFN locus on the sex-determining Z chromosome. Genetic, evolutionary and syntenic analyses indicate that chIFN-κ is a type I IFN with conserved genetic features and promoter binding sites. chIFN-κ regulated the IFN-stimulated response element signalling pathways and activated a panel of IFN-regulated genes, antiviral mediators and transcriptional regulators. Priming of chicken primary fibroblasts and tracheal organ cultures with chIFN-κ imparted cellular protections against viral infections both in vitro and ex vivo. To determine whether chIFN-κ defines the antiviral state in developing chicken embryos, we used replication-competent retroviral RCAS vector system to generate transgenic chicken embryos that constitutively and stably expressed chIFN-κ. We could demonstrate that chIFN-κ markedly inhibited the replication of avian RNA viruses in ovo. Collectively, these results shed the light on the repertoire of IFNs in avian species and provide functional data on the interaction of the chIFN-κ with RNA viruses of poultry and public health importance.