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Principal Investigator: Jason Scott McLellan
Organization: UNIVERSITY OF TEXAS AT AUSTIN
Fiscal Year: 2019
Award: $613,032
Funding agency: National Institute of Allergy and Infectious Diseases
Coronaviruses have the largest genomes among known RNA viruses and are phylogenetically divided into four
genera. Some betacoronaviruses, such as HKU1, circulate annually in humans and cause mild yet prevalent
respiratory disease whereas others, such as SARS-CoV and the recently emerged MERS-CoV, have caused
pandemics with high case-fatality rates. Due to their pandemic potential and airborne transmissibility, highly
pathogenic coronaviruses are now classified as NIAID Category C priority pathogens. Coronavirus cell tropism
and host range are in large part determined by the viral surface spike (S) glycoprotein, which is the largest
known class I viral fusion protein. After binding to host receptors and activation by host proteases, the S
proteins undergo large conformational rearrangements that result in fusion of the viral and host-cell
membranes. A molecular understanding of the structure, function and antigenicity of intact, trimeric S proteins
would identify sites of vulnerability that could be targeted by vaccines, therapeutic antibodies and small-
molecule antivirals. However, structural studies have been primarily limited to small S protein fragments, which
has precluded a unifying structural framework for the biology of coronavirus S proteins.
To address this knowledge gap, we have generated soluble, trimeric S proteins from HKU1 and MERS-
CoV that are amenable to structural analysis by X-ray crystallography and cryo-electron microscopy. We will
determine atomic-level structures of these S proteins in both the prefusion and postfusion conformations,
which will identify commonalities and differences among divergent betacoronaviruses and define the
conformational end-states of the fusion process (Aim 1). With these constructs and a range of biochemical and
biophysical assays, we will determine the molecular basis for receptor-induced conformational changes and
investigate the effects of host proteases and acidification on this process (Aim 2). The combination of these
studies will provide key molecular insights into S protein-mediated membrane fusion and answer long-standing
questions regarding S protein triggering. Similar to other class I fusion proteins, such as influenza
hemagglutinin (HA) and HIV-1 envelope (Env), coronavirus S proteins are the primary target for neutralizing
antibodies and are thus a critical component of developmental vaccines. Currently, the best-characterized
antibodies against coronaviruses target the receptor-binding domain (RBD) of the S protein and prevent
binding to host cells. The RBD, however, is the most variable part of the spike protein and antibodies that
target this domain are unlikely to be cross-reactive, similar to most HA head-binding antibodies. Therefore, we
will define the epitopes and mechanisms of antibody-mediated neutralization for novel, non-RBD-directed
neutralizing antibodies isolated by our collaborator Dr. Barney Graham (Aim 3). By identifying conserved sites
of vulnerability, these studies will provide the foundation for the development of immunotherapies and vaccines
that broadly protect against highly pathogenic betacoronaviruses, including those that have yet to emerge.
Terms: <Address><Adenosine Deaminase-Binding Proteins><Animals><Antibodies><Antibody Therapy><Antigenic Determinants><Antiviral Agents><Antiviral Drugs><Antivirals><Approaches to prevention><Assay><Binding><Binding Determinants><Bioassay><Biochemical><Biologic Assays><Biological Assay><Biology><Biophysics><C-terminal><CD26><CD26 Antigens><Case Fatality Rates><Category C pathogen><Category C priority pathogen><Cell Body><Cell membrane><Cells><Chimera Protein><Chimeric Proteins><Clinical Treatment Moab><Coronaviridae><Coronavirus><Coronavirus spike protein><Cryo-electron Microscopy><Cryoelectron Microscopy><Cytoplasmic Membrane><Development><Dipeptidyl-Peptidase IV><Elderly><Electron Cryomicroscopy><Epidemic><Epitopes><Esteroproteases><Fatality rate><Foundations><Fusion Protein><General Viruses><Genome><Glycans><Glycoproteins><Goals><HIV-1><HIV-I><HIV1><Head><Health><Hemagglutinin><Host Factor><Host Factor Protein><Human><Human Immunodeficiency Virus Type 1><Human immunodeficiency virus 1><Immunochemical Immunologic><Immunologic><Immunological><Immunologically><Immunologically Directed Therapy><Immunologics><Immunotherapy><Infant><Infection><Influenza HA><Influenza Hemagglutinin><Integration Host Factors><Knowledge><Laboratories><Lung diseases><MERS-CoV><Mediating><Membrane Fusion><Middle East Respiratory Syndrome><Middle East Respiratory Syndrome Coronavirus><Modern Man><Molecular><Molecular Configuration><Molecular Conformation><Molecular Interaction><Molecular Stereochemistry><Monoclonal Antibodies><Morbidity><Morbidity - disease rate><NIAID><National Institute of Allergy and Infectious Disease><Pathogenicity><Peptidases><Peptide Hydrolases><Phylogenetic Analysis><Phylogenetics><Plasma Membrane><Polysaccharides><Population><Prevention approach><Process><Protease Gene><Proteases><Protein Conformation><Protein Engineering><Protein Fragment><Proteinases><Proteins><Proteolytic Enzymes><Pulmonary Diseases><Pulmonary Disorder><RNA Viruses><Reagent><Receptor Activation><Receptor Cell><Receptor Protein><Resolution><Respiratory Disease><Respiratory System Disease><Respiratory System Disorder><Respiratory syncytial virus><SARS><Sampling><Severe Acute Respiratory Syndrome><Single Crystal Diffraction><Site><Structure><Surface><Technology><Therapeutic antibodies><Translating><Transmission><Tropism><Vaccine Antigen><Vaccine Design><Vaccines><Viral><Viral Fusion Glycoprotein><Viral Fusion Proteins><Viral Fusion-GP><Virus><Work><X Ray Crystallographies><X-Ray Crystallography><X-Ray Diffraction Crystallography><X-Ray/Neutron Crystallography><Xray Crystallography><Zoonoses><Zoonotic><Zoonotic Infection><advanced age><anti-viral agents><anti-viral drugs><anti-virals><antibody based therapies><antibody treatment><antibody-based therapeutics><antibody-based treatment><base><biophysical foundation><biophysical principles><biophysical sciences><combat><conformation><conformational state><cross reactivity><cryo-EM><cryoEM><developmental><disease of the lung><disorder of the lung><elders><flu HA><flu hemagglutinin><genetic protein engineering><geriatric><immune drugs><immune therapeutic approach><immune therapeutic interventions><immune therapeutic regimens><immune therapeutic strategy><immune therapy><immune-based therapies><immune-based treatments><immuno therapy><improved><influenza virus HA><influenza virus hemagglutinin><insight><late life><later life><lung disorder><mAbs><mortality><neutralizing antibody><neutralizing vaccine><new approaches><novel><novel approaches><novel strategies><novel strategy><older adult><older person><pandemic><pandemic disease><plasmalemma><prevent><preventing><protein design><receptor><receptor binding><receptor bound><senior citizen><small molecule><transmission process><virology><ward>