title: A camel-derived MERS-CoV with a variant spike protein cleavage site and distinct fusion activation properties.
abstract: Middle East respiratory syndrome coronavirus (MERS-CoV) continues to circulate in both humans and camels, and the origin and evolution of the virus remain unclear. Here we characterize the spike protein of a camel-derived MERS-CoV (NRCE-HKU205) identified in 2013, early in the MERS outbreak. NRCE-HKU205 spike protein has a variant cleavage motif with regard to the S2' fusion activation site-notably, a novel substitution of isoleucine for the otherwise invariant serine at the critical P1' cleavage site position. The substitutions resulted in a loss of furin-mediated cleavage, as shown by fluorogenic peptide cleavage and western blot assays. Cell-cell fusion and pseudotyped virus infectivity assays demonstrated that the S2' substitutions decreased spike-mediated fusion and viral entry. However, cathepsin and trypsin-like protease activation were retained, albeit with much reduced efficiency compared with the prototypical EMC/2012 human strain. We show that NRCE-HKU205 has more limited fusion activation properties possibly resulting in more restricted viral tropism and may represent an intermediate in the complex pattern of MERS-CoV ecology and evolution.
authors.affiliation: Department of Microbiology and Immunology, College of Veterinary Medicine, Cornell University, Ithaca, NY 14853, USA.
authors.forename: Jean Kaoru
authors.initials: JK
authors.lastname: Millet
authors.affiliation: Department of Microbiology and Immunology, College of Veterinary Medicine, Cornell University, Ithaca, NY 14853, USA.|Cornell Undergraduate Biology, Cornell University, Ithaca, NY 14853, USA.
authors.forename: Monty E
authors.initials: ME
authors.lastname: Goldstein
authors.affiliation: Department of Microbiology and Immunology, College of Veterinary Medicine, Cornell University, Ithaca, NY 14853, USA.|Cornell DVM Program, Cornell University, Ithaca, NY 14853, USA.
authors.forename: Rachael N
authors.initials: RN
authors.lastname: Labitt
authors.affiliation: School of Chemical and Biomolecular Engineering, Cornell University, Ithaca, NY 14853, USA.|Cornell Graduate Field of Chemical and Biomolecular Engineering, Cornell University, Ithaca, NY 14853, USA.
authors.forename: Hung-Lun
authors.initials: HL
authors.lastname: Hsu
authors.affiliation: School of Chemical and Biomolecular Engineering, Cornell University, Ithaca, NY 14853, USA.
authors.forename: Susan
authors.initials: S
authors.lastname: Daniel
authors.affiliation: Department of Microbiology and Immunology, College of Veterinary Medicine, Cornell University, Ithaca, NY 14853, USA.
authors.forename: Gary R
authors.initials: GR
authors.lastname: Whittaker
mesh_terms: D019943:Amino Acid Substitution; D000818:Animals; D002162:Camelus / Q000821:virology*; D002460:Cell Line; D045683:Furin / Q000378:metabolism; D006801:Humans; D007532:Isoleucine / Q000235:genetics; D065207:Middle East Respiratory Syndrome Coronavirus / Q000235:genetics* / Q000302:isolation & purification* / Q000502:physiology; D059748:Proteolysis; D012694:Serine / Q000235:genetics; D064370:Spike Glycoprotein, Coronavirus / Q000235:genetics* / Q000378:metabolism; D053586:Virus Internalization
chemical_list: D064370:Spike Glycoprotein, Coronavirus; D007532:Isoleucine; D012694:Serine; D045683:Furin