Antiviral activity of rChIFN-α against vesicular stomatitis virus and Newcastle disease virus: A novel recombinant chicken interferon-α showed high antiviral activity

Soluble expression, rapid purification, biological identification of chicken interferon-alpha using a thioredoxin fusion system in E. coli and its antiviral effects to H9N2 avian influenza virus

In this paper, we report a soluble expression based on Escherichia coli and two-step purification of a novel thioredoxin-tagged chicken interferon-α fusion protein (Trx-rChIFN-α) by using pET32a(+) expression system. The mature ChIFN-α gene was amplified by Reverse transcriptase-polymerase chain reaction (RT-PCR) and subcloned into pET-32a (+) vector prior to transformation into Rosetta (DE3) competent cells. After IPTG induction, the recombinant fusion protein was expressed efficiently in the soluble fraction. The protein purification was performed by nickel affinity chromatography and DEAE anion exchange chromatography. The purified product has a purity of 95% with a yield of 47.3 mg/L of culture. The specific activity of the fusion protein reaches to 2.0 × 10⁷ IU/mg as determined in the CEF/VSV titration system. After excision of the Trx tag by enterokinase, the remaining solo protein was confirmed as rChIFN-α protein by SDS-PAGE, N-terminal sequencing and mass spectrometry. The effects of this Trx-rChIFN-α fusion protein against H9N2 influenza virus infection were also evaluated in ovo. The results showed that the Trx-rChIFN-α protein could significantly reduce the hemagglutination titer of H9N2 virus, and the H9N2 viruses HA gene copy numbers. These findings will enable us to produce large amount and bio-active rChIFN-α protein for future applications.

Immune responses of mature chicken bone-marrow-derived dendritic cells infected with Newcastle disease virus strains with differing pathogenicity

Infection of chickens with virulent Newcastle disease virus (NDV) is associated with severe pathology and increased morbidity and mortality. The innate immune response contributes to the pathogenicity of NDV. As professional antigen-presenting cells, dendritic cells (DCs) play a unique role in innate immunity. However, the contribution of DCs to NDV infection has not been investigated in chickens. In this study, we selected two representative NDV strains, i.e., the velogenic NDV strain Chicken/Guangdong/GM/2014 (GM) and the lentogenic NDV strain La Sota, to investigate whether NDVs could infect LPS-activated chicken bone-derived marrow DCs (mature chicken BM-DCs). We compared the viral titres and innate immune responses in mature chicken BM-DCs following infection with those strains. Both NDV strains could infect mature chicken BM-DC, but the GM strain showed stronger replication capacity than the La Sota strain in mature chicken BM-DCs. Gene expression profiling showed that MDA5, LGP2, TLR3, TLR7, IFN-α, IFN-β, IFN-γ, IL-1β, IL-6, IL-18, IL-8, CCL5, IL-10, IL-12, MHC-I, and MHC-II levels were altered in mature DCs after infection with NDVs at all evaluated times postinfection. Notably, the GM strain triggered stronger innate immune responses than the La Sota strain in chicken BM-DCs. However, both strains were able to suppress the expression of some cytokines, such as IL-6 and IFN-α, in mature chicken DCs at 24 hpi. These data provide a foundation for further investigation of the role of chicken DCs in NDV infection.

Characterization of bovine interferon α1: expression in yeast Pichia pastoris, biological activities, and physicochemical characteristics

A bovine interferon α (BoIFNα) gene that included signal sequence was amplified from bovine liver genomic DNA. The gene was named BoIFN-α1 according to the position at which the encoded gene of the bovine IFN was located in the bovine genome. The sequence included a 23-amino-acid signal peptide and a 166-amino-acid mature peptide. The structural characteristics and phylogenetic relationships of the BoIFN-α1 gene were analyzed. A recombinant mature BoIFN-α1 (rBoIFN-α1) was expressed in the yeast Pichia pastoris. Physicochemical characteristics and antiviral activity were determined in vitro. Recombinant BoIFN-α1 was found to be highly sensitive to trypsin and stable at pH 2.0 or 65°C. It also exhibited antiviral activity, which was neutralized by a rabbit anti-rBoIFNα polyclonal antibody. This study revealed that rBoIFN-α1 has the typical characteristics of IFNα and can be used for both research and industrial application.

Potential applications for antiviral therapy and prophylaxis in bovine medicine

Viral disease is one of the major causes of financial loss and animal suffering in today's cattle industry. Increases in global commerce and average herd size, urbanization, vertical integration within the industry and alterations in global climate patterns have allowed the spread of pathogenic viruses, or the introduction of new viral species, into regions previously free of such pathogens, creating the potential for widespread morbidity and mortality in naïve cattle populations. Despite this, no antiviral products are currently commercially licensed for use in bovine medicine, although significant progress has been made in the development of antivirals for use against bovine viral diarrhea virus (BVDV), foot and mouth disease virus (FMDV) and bovine herpesvirus (BHV). BVDV is extensively studied as a model virus for human antiviral studies. Consequently, many compounds with efficacy have been identified and a few have been successfully used to prevent infection in vivo although commercial development is still lacking. FMDV is also the subject of extensive antiviral testing due to the importance of outbreak containment for maintenance of export markets. Thirdly, BHV presents an attractive target for antiviral development due to its worldwide presence. Antiviral studies for other bovine viral pathogens are largely limited to preliminary studies. This review summarizes the current state of knowledge of antiviral compounds against several key bovine pathogens and the potential for commercial antiviral applications in the prevention and control of several selected bovine diseases.

Engagement of soluble resistance-related calcium binding protein (sorcin) with foot-and-mouth disease virus (FMDV) VP1 inhibits type I interferon response in cells

Foot-and-mouth disease (FMD) is an acute, highly contagious animal disease caused by FMD virus (FMDV). Although FMDV-induced immunosuppression in host has been well established, the exact molecular mechanism for such induction is not very clear. We report here the identification of FMDV VP1 as an interferon-suppressor by interacting with soluble resistance-related calcium binding protein (sorcin). We found that VP1 suppressed tumor necrosis factor (TNF)-α or Sendai virus (SeV)-induced type I interferon response in HEK293T cells, and that this suppression could be completely abolished by knockdown of sorcin by shRNA. Furthermore, overexpression of sorcin inhibited type I interferon response. Conversely, TNF- or SeV-induced type I interferon response increased when sorcin knocked down, leading to inhibition of vesicular stomatitis virus (VSV) replication. Thus, VP1-induced suppression of type I interferon is mediated by interacting with sorcin, a protein that appears to regulate cell response to viral infections.