title: Selection of and recombination between minor variants lead to the adaptation of an avian coronavirus to primate cells.
abstract: An interesting question posed by the current evidence that severe acute respiratory syndrome coronavirus may be originated from an animal coronavirus is how such an animal coronavirus breaks the host species barrier and becomes zoonotic. In this report, we study the chronological order of genotypic changes in the spike protein of avian coronavirus infectious bronchitis virus (IBV) during its adaptation to a primate cell line. Adaptation of the Beaudette strain of IBV from chicken embryo to Vero cells showed the accumulation of 49 amino acid mutations. Among them, 26 (53.06%) substitutions were located in the S protein. Sequencing analysis and comparison of the S gene demonstrated that the majority of the mutations were accumulated and fixed at passage 7 on Vero cells and minor variants were isolated in several passages. Evidence present suggests that the dominant Vero cell-adapted IBV strain may be derived from the chicken embryo passages by selection of and potential recombination between the minor variants. This may explain why adaptation is a rapid process and the dominant strain, once adapted to a new host cell, becomes relatively stable.
authors.affiliation: Institute of Molecular and Cell Biology, 61 Biopolis Drive, Proteos, Singapore 138673, Singapore.
authors.forename: Shou Guo
authors.initials: SG
authors.lastname: Fang
authors.forename: Shuo
authors.initials: S
authors.lastname: Shen
authors.forename: Felicia P L
authors.initials: FP
authors.lastname: Tay
authors.forename: D X
authors.initials: DX
authors.lastname: Liu
mesh_terms: D000222:Adaptation, Physiological / Q000235:genetics*; D000595:Amino Acid Sequence; D000818:Animals; D002645:Chickens / Q000821:virology*; D002522:Chlorocebus aethiops / Q000821:virology*; D022761:Gene Transfer, Horizontal / Q000235:genetics; D014644:Genetic Variation / Q000235:genetics; D001351:Infectious bronchitis virus / Q000235:genetics*; D008562:Membrane Glycoproteins / Q000737:chemistry / Q000235:genetics*; D008969:Molecular Sequence Data; D011323:Primates / Q000821:virology; D011995:Recombination, Genetic / Q000235:genetics*; D012641:Selection, Genetic; D064370:Spike Glycoprotein, Coronavirus; D014709:Vero Cells; D014759:Viral Envelope Proteins / Q000737:chemistry / Q000235:genetics*
chemical_list: D008562:Membrane Glycoproteins; D064370:Spike Glycoprotein, Coronavirus; D014759:Viral Envelope Proteins; C578557:spike glycoprotein, SARS-CoV; C578553:spike protein, mouse hepatitis virus