title: Pathways of cross-species transmission of synthetically reconstructed zoonotic severe acute respiratory syndrome coronavirus.
abstract: Zoonotic severe acute respiratory syndrome coronavirus (SARS-CoV) likely evolved to infect humans by a series of transmission events between humans and animals in markets in China. Virus sequence data suggest that the palm civet served as an amplification host in which civet and human interaction fostered the evolution of the epidemic SARS Urbani strain. The prototypic civet strain of SARS-CoV, SZ16, was isolated from a palm civet but has not been successfully cultured in vitro. To propagate a chimeric recombinant SARS-CoV bearing an SZ16 spike (S) glycoprotein (icSZ16-S), we constructed cell lines expressing the civet ortholog (DBT-cACE2) of the SARS-CoV receptor (hACE2). Zoonotic SARS-CoV was completely dependent on ACE2 for entry. Urbani grew with similar kinetics in both the DBT-cACE2 and the DBT-hACE2 cells, while icSZ16-S only grew in DBT-cACE2 cells. The SZ16-S mutant viruses adapted to human airway epithelial cells and displayed enhanced affinity for hACE2 but exhibited severe growth defects in the DBT-cACE2 cells, suggesting that the evolutionary pathway that promoted efficient hACE2 interactions simultaneously abolished efficient cACE2 interactions. Structural modeling predicted two distinct biochemical interaction networks by which zoonotic receptor binding domain architecture can productively engage hACE2, but only the Urbani mutational repertoire promoted efficient usage of both hACE2 and cACE2 binding interfaces. Since dual species tropism was preserved in Urbani, it is likely that the virus evolved a high affinity for cACE2/hACE2 receptors through adaptation via repeated passages between human and civet hosts. Furthermore, zoonotic SARS-CoV was variably neutralized by antibodies that were effective against the epidemic strain, highlighting their utility for evaluating passive immunization efficacy.
authors.affiliation: Department of Microbiology and Immunology, University of North Carolina, Chapel Hill, North Carolina 27699-7435, USA.
authors.forename: Timothy
authors.initials: T
authors.lastname: Sheahan
authors.forename: Barry
authors.initials: B
authors.lastname: Rockx
authors.forename: Eric
authors.initials: E
authors.lastname: Donaldson
authors.forename: Davide
authors.initials: D
authors.lastname: Corti
authors.forename: Ralph
authors.initials: R
authors.lastname: Baric
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D000911:Antibodies, Monoclonal / Q000276:immunology; D002460:Cell Line; D002681:China / Q000453:epidemiology; D002685:Chiroptera / Q000821:virology*; D002522:Chlorocebus aethiops; D003588:Cytopathogenic Effect, Viral; D004197:Disease Reservoirs; D005814:Genes, Viral; D049452:Green Fluorescent Proteins / Q000378:metabolism; D006801:Humans; D007700:Kinetics; D008562:Membrane Glycoproteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009500:Neutralization Tests; D010957:Plasmids; D017354:Point Mutation; D011485:Protein Binding; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D011991:Receptors, Virus / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D045473:Severe acute respiratory syndrome-related coronavirus / Q000254:growth & development / Q000302:isolation & purification / Q000472:pathogenicity*; D017422:Sequence Analysis, DNA; D045169:Severe Acute Respiratory Syndrome / Q000453:epidemiology / Q000209:etiology / Q000473:pathology; D064370:Spike Glycoprotein, Coronavirus; D013698:Templates, Genetic; D014162:Transfection; D014709:Vero Cells; D014759:Viral Envelope Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D045949:Viverridae / Q000821:virology*; D015047:Zoonoses / Q000453:epidemiology / Q000635:transmission* / Q000821:virology*
chemical_list: D000911:Antibodies, Monoclonal; D008562:Membrane Glycoproteins; D011991:Receptors, Virus; D064370:Spike Glycoprotein, Coronavirus; D014759:Viral Envelope Proteins; D049452:Green Fluorescent Proteins