• CD8+ T cells and macrophages regulate pathogenesis in a mouse model of Middle East respiratory syndrome

      Coleman, C.M.; Halasz, G.; Zhong, J.; Beck, S.E.; Matthews, K.L.; Venkataraman, T.; Rajagopalan, S.; Frieman, M.B. (American Society for Microbiology, 2017)
      Middle East respiratory syndrome coronavirus (MERS-CoV) is an important emerging pathogen that was first described in 2012. While the cell surface receptor for MERS-CoV has been identified as dipeptidyl peptidase 4 (DPP4), the mouse DPP4 homologue does not allow virus entry into cells. Therefore, development of mouse models of MERS-CoV has been hampered by the fact that MERS-CoV does not replicate in commonly available mouse strains. We have previously described a mouse model in which mDPP4 was replaced with hDPP4 such that hDPP4 is expressed under the endogenous mDPP4 promoter. In this study, we used this mouse model to analyze the host response to MERS-CoV infection using immunological assays and transcriptome analysis. Depletion of CD4+ T cells, CD8+ T cells, or macrophages has no effect on MERS-CoV replication in the lungs of infected mice. However, we found that depletion of CD8+ T cells protects and depletion of macrophages exacerbates MERS-CoV-induced pathology and clinical symptoms of disease. Overall, we demonstrate an important role for the inflammatory response in regulating MERS-CoV pathogenesis in vivo.
    • MERS-CoV spike nanoparticles protect mice from MERS-CoV infection

      Coleman, C.M.; Venkataraman, T.; Frieman, M.B. (Elsevier Ltd, 2017)
      The Middle East respiratory syndrome coronavirus (MERS-CoV) was first discovered in late 2012 and has gone on to cause over 1800 infections and 650 deaths. There are currently no approved therapeutics or vaccinations for MERS-CoV. The MERS-CoV spike (S) protein is responsible for receptor binding and virion entry to cells, is immunodominant and induces neutralizing antibodies in vivo, all of which, make the S protein an ideal target for anti-MERS-CoV vaccines. In this study, we demonstrate protection induced by vaccination with a recombinant MERS-CoV S nanoparticle vaccine and Matrix-M1 adjuvant combination in mice. The MERS-CoV S nanoparticle vaccine produced high titer anti-S neutralizing antibody and protected mice from MERS-CoV infection in vivo.
    • Overactive epidermal growth factor receptor signaling leads to increased fibrosis after severe acute respiratory syndrome coronavirus infection

      Venkataraman, T.; Coleman, C.M.; Frieman, M.B. (American Society for Microbiology, 2017)
      Severe acute respiratory syndrome coronavirus (SARS-CoV) is a highly pathogenic respiratory virus that causes morbidity and mortality in humans. After infection with SARS-CoV, the acute lung injury caused by the virus must be repaired to regain lung function. A dysregulation in this wound healing process leads to fibrosis. Many survivors of SARS-CoV infection develop pulmonary fibrosis (PF), with higher prevalence in older patients. Using mouse models of SARS-CoV pathogenesis, we have identified that the wound repair pathway, controlled by the epidermal growth factor receptor (EGFR), is critical to recovery from SARS-CoV-induced tissue damage. In mice with constitutively active EGFR [EGFR(DSK5) mice], we find that SARS-CoV infection causes enhanced lung disease. Importantly, we show that during infection, the EGFR ligands amphiregulin and heparin-binding EGF-like growth factor (HB-EGF) are upregulated, and exogenous addition of these ligands during infection leads to enhanced lung disease and altered wound healing dynamics. Our data demonstrate a key role of EGFR in the host response to SARS-CoV and how it may be implicated in lung disease induced by other highly pathogenic respiratory viruses.
    • Repurposing of clinically developed drugs for treatment of Middle East respiratory syndrome coronavirus infection

      Coleman, C.M.; Venkataraman, T.; Frieman, M.B. (American Society for Microbiology, 2014)
      Outbreaks of emerging infections present health professionals with the unique challenge of trying to select appropriate pharmacologic treatments in the clinic with little time available for drug testing and development. Typically, clinicians are left with general supportive care and often untested convalescent-phase plasma as available treatment options. Repurposing of approved pharmaceutical drugs for new indications presents an attractive alternative to clinicians, researchers, public health agencies, drug developers, and funding agencies. Given the development times and manufacturing requirements for new products, repurposing of existing drugs is likely the only solution for outbreaks due to emerging viruses. In the studies described here, a library of 290 compounds was screened for antiviral activity against Middle East respiratory syndrome coronavirus (MERS-CoV) and severe acute respiratory syndrome coronavirus (SARS-CoV). Selection of compounds for inclusion in the library was dependent on current or previous FDA approval or advanced clinical development. Some drugs that had a well-defined cellular pathway as target were included. In total, 27 compounds with activity against both MERS-CoV and SARS-CoV were identified. The compounds belong to 13 different classes of pharmaceuticals, including inhibitors of estrogen receptors used for cancer treatment and inhibitors of dopamine receptor used as antipsychotics. The drugs identified in these screens provide new targets for in vivo studies as well as incorporation into ongoing clinical studies.
    • The role of epidermal growth factor receptor (EGFR) signaling in SARS coronavirus-induced pulmonary fibrosis

      Venkataraman, T.; Frieman, M.B. (Elsevier B.V., 2017)
      Many survivors of the 2003 outbreak of severe acute respiratory syndrome (SARS) developed residual pulmonary fibrosis with increased severity seen in older patients. Autopsies of patients that died from SARS also showed fibrosis to varying extents. Pulmonary fibrosis can be occasionally seen as a consequence to several respiratory viral infections but is much more common after a SARS coronavirus (SARS-CoV) infection. Given the threat of future outbreaks of severe coronavirus disease, including Middle East respiratory syndrome (MERS), it is important to understand the mechanisms responsible for pulmonary fibrosis, so as to support the development of therapeutic countermeasures and mitigate sequelae of infection. In this article, we summarize pulmonary fibrotic changes observed after a SARS-CoV infection, discuss the extent to which other respiratory viruses induce fibrosis, describe available animal models to study the development of SARS-CoV induced fibrosis and review evidence that pulmonary fibrosis is caused by a hyperactive host response to lung injury mediated by epidermal growth factor receptor (EGFR) signaling. We summarize work from our group and others indicating that inhibiting EGFR signaling may prevent an excessive fibrotic response to SARS-CoV and other respiratory viral infections and propose directions for future research.
    • Severe acute respiratory syndrome coronavirus ORF7a inhibits bone marrow stromal antigen 2 virion tethering through a novel mechanism of glycosylation interference

      Taylor, J.K.; Coleman, C.M.; Postel, S.; Sisk, J.M.; Venkataraman, T.; Sundberg, E.J.; Frieman, M.B. (American Society for Microbiology, 2015)
      Severe acute respiratory syndrome (SARS) emerged in November 2002 as a case of atypical pneumonia in China, and the causative agent of SARS was identified to be a novel coronavirus, severe acute respiratory syndrome coronavirus (SARS-CoV). Bone marrow stromal antigen 2 (BST-2; also known as CD317 or tetherin) was initially identified to be a pre-B-cell growth promoter, but it also inhibits the release of virions of the retrovirus human immunodeficiency virus type 1 (HIV-1) by tethering budding virions to the host cell membrane. Further work has shown that BST-2 restricts the release of many other viruses, including the human coronavirus 229E (hCoV-229E), and the genomes of many of these viruses encode BST-2 antagonists to overcome BST-2 restriction. Given the previous studies on BST-2, we aimed to determine if BST-2 has the ability to restrict SARS-CoV and if the SARS-CoV genome encodes any proteins that modulate BST-2's antiviral function. Through an in vitro screen, we identified four potential BST-2 modulators encoded by the SARS-CoV genome: the papain-like protease (PLPro), nonstructural protein 1 (nsp1), ORF6, and ORF7a. As the function of ORF7a in SARS-CoV replication was previously unknown, we focused our study on ORF7a. We found that BST-2 does restrict SARS-CoV, but the loss of ORF7a leads to a much greater restriction, confirming the role of ORF7a as an inhibitor of BST-2. We further characterized the mechanism of BST-2 inhibition by ORF7a and found that ORF7a localization changes when BST-2 is overexpressed and ORF7a binds directly to BST-2. Finally, we also show that SARSCoV ORF7a blocks the restriction activity of BST-2 by blocking the glycosylation of BST-2.