title: Establishment of Subclones of the Severe Fever with Thrombocytopenia Syndrome Virus YG1 Strain Selected Using Low pH-Dependent Cell Fusion Activity.
abstract: The first clinical case of the YG1 strain of the severe fever with thrombocytopenia syndrome virus (SFTSV) has been isolated in Japan. We found that only some of the cells underwent low pH-dependent cell fusion, although all of the cells were confirmed to have been infected with the virus. This suggested that the YG1 strain consists of a heterogeneous mixture of related viruses. Here, we established 3 subclones (termed E3, A4, and B7) from the YG1 strain, using the limiting dilution method with the pH-dependent cell fusion activity. Subclone E3 showed weak fusion activity and cytopathic effects (CPE) in Vero E6 cells. The amino acid sequence of E3 was identical to the published sequence for the YG1 strain, and it likely comprises a subpopulation of the YG1 strain. Subclone A4 displayed strong fusion activity under acidic conditions. In contrast, subclone B7 showed strong fusion activity and CPE under neutral and acidic conditions. Two amino acid differences shared between B7 and A4 were found in the envelope glycoproteins. In addition, an amino acid variant of the RNA-dependent RNA polymerase was found only in B7. These subclones will be valuable tools to elucidate cell fusion mechanisms of SFTSV and the relationship between viral proteins and their functions.
authors.affiliation: Department of Microbiology, Hokkaido University Graduate School of Medicine.
authors.forename: Sanae
authors.initials: S
authors.lastname: Nishio
authors.affiliation: Department of Microbiology, Hokkaido University Graduate School of Medicine.
authors.forename: Yoshimi
authors.initials: Y
authors.lastname: Tsuda
authors.affiliation: Department of Microbiology, Hokkaido University Graduate School of Medicine.
authors.forename: Ryo
authors.initials: R
authors.lastname: Ito
authors.affiliation: Department of Microbiology, Hokkaido University Graduate School of Medicine.
authors.forename: Kenta
authors.initials: K
authors.lastname: Shimizu
authors.affiliation: Department of Microbiology, Hokkaido University Graduate School of Medicine.
authors.forename: Kumiko
authors.initials: K
authors.lastname: Yoshimatsu
authors.affiliation: Department of Microbiology, Hokkaido University Graduate School of Medicine.
authors.forename: Jiro
authors.initials: J
authors.lastname: Arikawa
mesh_terms: D019943:Amino Acid Substitution; D000818:Animals; D002459:Cell Fusion; D002522:Chlorocebus aethiops; D003588:Cytopathogenic Effect, Viral; D005838:Genotype; D054884:Host-Pathogen Interactions; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007564:Japan; D010217:Phlebotomus Fever / Q000821:virology*; D016856:Phlebovirus / Q000145:classification* / Q000235:genetics / Q000302:isolation & purification / Q000502:physiology*; D014709:Vero Cells; D014759:Viral Envelope Proteins / Q000235:genetics
chemical_list: D014759:Viral Envelope Proteins
keywords: SFTSV; cell fusion; quasispecies; subclone