title: Putative RNA viral sequences detected in an Ixodes scapularis-derived cell line.
abstract: Ticks harbour various microorganisms, some of which act as pathogens of humans and animals. The recent advancement of genome sequencing technologies revealed that a wide range of previously unrecognised microorganisms exist in ticks. Continuous cell lines established from ticks could play a key role in the isolation of such microorganisms; however, tick cells themselves have been known to harbour symbiotic microorganisms. The present study aimed to characterise putative RNA viral sequences detected in the culture supernatant of one of the most frequently used tick cell lines, ISE6, which was derived from embryos of the blacklegged tick Ixodes scapularis. Viral particles purified from the culture supernatant were used for RNA extraction, followed by Illumina sequencing. The reads were de novo assembled and the resulting contigs were annotated by tBLASTx search. The results suggested that there were at least five putative viral sequences of four phylogenetically distinct lineages in ISE6 cells. The predominant viral sequence found in ISE6 cells, designated I. scapularis iflavirus, was a member of the family Iflaviridae, which is an arthropod-infecting virus group. We also identified L and M segments of the family Bunyaviridae, which could not be classified into any of the five known genera, and a potential capsid protein related to Drosophila A virus. In addition to these previously unrecognised viruses, ISE6 was revealed to harbour a putative genome sequence of I. scapularis-associated virus-1, which was reported in a recent metagenomic study of I. scapularis itself. All the five putative viral sequences were detected by RT-PCR in both ISE6 cells and the culture supernatant. Electron microscopic analysis showed the existence of spherical virions with a varying diameter of 50-70nm in the culture supernatant of ISE6 cells. Further studies are required to investigate the potential roles of ISE6-associated viruses in ticks.
authors: Unit of Risk Analysis and Management, Hokkaido University Research Center for Zoonosis Control, Sapporo, Japan; Laboratory of Parasitology, Department of Disease Control, Graduate School of Veterinary Medicine, Hokkaido University, Sapporo, Japan. Electronic address: ryo.nakao@vetmed.hokudai.ac.jp.
authors: Ryo
authors: R
authors: Nakao
authors: Laboratory of Microbiology, Department of Disease Control, Graduate School of Veterinary Medicine, Hokkaido University, Sapporo, Japan; Global Institution for Collaborative Research and Education, Hokkaido University, Sapporo, Japan.
authors: Keita
authors: K
authors: Matsuno
authors: Division of Collaboration and Education, Hokkaido University Research Center for Zoonosis Control, Sapporo, Japan.
authors: Yongjin
authors: Y
authors: Qiu
authors: Division of Global Epidemiology, Hokkaido University Research Center for Zoonosis Control, Sapporo, Japan.
authors: Junki
authors: J
authors: Maruyama
authors: Division of Global Epidemiology, Hokkaido University Research Center for Zoonosis Control, Sapporo, Japan.
authors: Nao
authors: N
authors: Eguchi
authors: Division of Global Epidemiology, Hokkaido University Research Center for Zoonosis Control, Sapporo, Japan.
authors: Naganori
authors: N
authors: Nao
authors: Division of Global Epidemiology, Hokkaido University Research Center for Zoonosis Control, Sapporo, Japan.
authors: Masahiro
authors: M
authors: Kajihara
authors: Laboratory of Public Health, Department of Disease Control, Graduate School of Veterinary Medicine, Hokkaido University, Sapporo, Japan.
authors: Kentaro
authors: K
authors: Yoshii
authors: Global Institution for Collaborative Research and Education, Hokkaido University, Sapporo, Japan; Division of Molecular Pathobiology, Hokkaido University Research Center for Zoonosis Control, Sapporo, Japan; Department of Disease Control, School of Veterinary Medicine, University of Zambia, Lusaka, Zambia; Global Virus Network, Baltimore, USA.
authors: Hirofumi
authors: H
authors: Sawa
authors: Global Institution for Collaborative Research and Education, Hokkaido University, Sapporo, Japan; Division of Global Epidemiology, Hokkaido University Research Center for Zoonosis Control, Sapporo, Japan; Department of Disease Control, School of Veterinary Medicine, University of Zambia, Lusaka, Zambia.
authors: Ayato
authors: A
authors: Takada
authors: Global Institution for Collaborative Research and Education, Hokkaido University, Sapporo, Japan; Division of Collaboration and Education, Hokkaido University Research Center for Zoonosis Control, Sapporo, Japan; Department of Disease Control, School of Veterinary Medicine, University of Zambia, Lusaka, Zambia.
authors: Chihiro
authors: C
authors: Sugimoto
mesh_terms: D000818:Animals; D002460:Cell Line; D018884:Ixodes / Q000166:cytology*; D016851:Orthobunyavirus / Q000235:genetics*; D010802:Phylogeny; D010849:Picornaviridae / Q000235:genetics*; D012367:RNA, Viral / Q000302:isolation & purification*
chemical_list: D012367:RNA, Viral
keywords: Bunyavirus; ISE6; Iflavirus; Ixodes scapularis; Ixodes scapularis-associated virus-1