title: Mutations in the spike gene of porcine epidemic diarrhea virus associated with growth adaptation in vitro and attenuation of virulence in vivo.
abstract: Previously, we have reported that a serial passage of 83P-5 strain of porcine epidemic diarrhea virus (PEDV) in Vero cells resulted in a growth adaptation of the virus in cultured cells at the 22nd passage. In this study, we further maintained the 83P-5 in Vero cells up to the 100th passage and analyzed changes in the spike (S), membrane (M), and nucleocapsid (N) gene sequences and pathogenicity of the virus at the 34th, 61st, and 100th passage levels. Sequence analyses revealed a strong selection for the S gene of 83P-5 in Vero cells, and virtually all mutations occurring at the 34th and 61st passages had been carried over to the 100th-passaged virus. In contrast, the viral M and N genes showed a strong conservation during the serial passage. Pigs experimentally infected with the 34th- or 61st-passaged virus, but not the 100th-passaged virus, exhibited diarrhea, indicating an attenuation of the 83P-5 at the 100th passage. Interestingly, S protein of the attenuated 100th-passaged 83P-5 showed a remarkable sequence similarity to that of previously reported DR-13 strain of attenuated PEDV that also had been established by serial passage in Vero cells. Further studies will be required to define whether the mutations in the S gene of 83P-5 that had been selected and accumulated during the serial passages are indeed the causalities of the growth adaptation in vitro and the attenuation of virulence in vivo.
authors.affiliation: Nippon Institute for Biological Science, 9-2221-1 Shin-machi, Ome, Tokyo, 198-0024, Japan. tetsuo_s@nibs.or.jp
authors.forename: Tetsuo
authors.initials: T
authors.lastname: Sato
authors.forename: Natsumi
authors.initials: N
authors.lastname: Takeyama
authors.forename: Atsushi
authors.initials: A
authors.lastname: Katsumata
authors.forename: Kotaro
authors.initials: K
authors.lastname: Tuchiya
authors.forename: Toshiaki
authors.initials: T
authors.lastname: Kodama
authors.forename: Ko-ichi
authors.initials: K
authors.lastname: Kusanagi
mesh_terms: D000220:Adaptation, Biological; D000818:Animals; D002522:Chlorocebus aethiops; D000086862:Coronavirus M Proteins; D000086462:Coronavirus Nucleocapsid Proteins; D004252:DNA Mutational Analysis; D008562:Membrane Glycoproteins / Q000235:genetics*; D008969:Molecular Sequence Data; D020125:Mutation, Missense; D019590:Nucleocapsid Proteins; D053485:Porcine epidemic diarrhea virus / Q000235:genetics* / Q000254:growth & development* / Q000472:pathogenicity; D012367:RNA, Viral / Q000235:genetics; D017422:Sequence Analysis, DNA; D012692:Serial Passage; D064370:Spike Glycoprotein, Coronavirus; D014709:Vero Cells; D014759:Viral Envelope Proteins / Q000235:genetics*; D014763:Viral Matrix Proteins / Q000235:genetics; D014774:Virulence
chemical_list: D000086862:Coronavirus M Proteins; D000086462:Coronavirus Nucleocapsid Proteins; C000706236:M protein, Porcine epidemic diarrhea virus; D008562:Membrane Glycoproteins; D019590:Nucleocapsid Proteins; D012367:RNA, Viral; D064370:Spike Glycoprotein, Coronavirus; D014759:Viral Envelope Proteins; D014763:Viral Matrix Proteins; C578557:spike glycoprotein, SARS-CoV; C578553:spike protein, mouse hepatitis virus