Two new species of betatorqueviruses identified in a human melanoma that metastasized to the brain
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Terry Fei Fan Ng1,2,3,5, Jennifer A. Dill3, Alvin C. Camus3, Eric Delwart1,2,* and Erwin G. Van Meir4,*
1Blood Systems Research Institute, San Francisco, California, USA
2Department of Laboratory Medicine, University of California at San Francisco, San Francisco, California, USA
3Department of Pathology, University of Georgia, Athens, Georgia, USA
4Departments of Neurosurgery and Hematology & Medical Oncology, Winship Cancer Institute and School of Medicine, Emory University, Atlanta, Georgia, USA
5Current/Present address: DVD, NCIRD, Centers for Disease Control and Prevention, Atlanta, Georgia, USA
Terry Fei Fan Ng, email: [email protected]
Keywords: brain tumor; neuro-oncology; anellovirus; metagenomics; metastasis
Received: September 19, 2017 Accepted: October 25, 2017 Published: November 11, 2017
The role of viral infections in the etiology of brain cancer remains uncertain. Prior studies mostly focused on transcriptome or viral DNA integrated in tumor cells. To investigate for the presence of viral particles, we performed metagenomics sequencing on viral capsid-protected nucleic acids from 12 primary and 8 metastatic human brain tumors. One brain tumor metastasized from a skin melanoma harbored two new human anellovirus species, Torque teno mini virus Emory1 (TTMV Emory1) and Emory2 (TTMV Emory2), while the remaining 19 samples did not reveal any exogenous viral sequences. Their genomes share 63-67% identity with other TTMVs, and phylogenetic clustering supports their classification within the Betatorquevirus genus. This is the first identification of betatorqueviruses in brain tumors. The viral DNA was in its expected non-integrated circular form, and it is unclear if the viruses contributed to tumor formation. Whether the viruses originated from blood, or the primary skin tumor could not be ascertained. Overall, our results demonstrate the usefulness of viral metagenomics to detect previously unknown exogenous virus in human brain tumors. They further suggest that active viral infections are rare events in brain tumors, but support a follow-up larger scale study to quantify their frequency in different brain tumor subtypes.
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