Characterization of the non-coding control region of polyomavirus KI isolated from nasopharyngeal samples from patients with respiratory symptoms or infection and from blood from healthy blood donors in Norway

Abstract

Seroepidemiological studies showed that the human polyomavirus KI (KIPyV) is common in the human population, with age-specific seroprevalence ranging from 40-90 %. Genome epidemiological analyses demonstrated that KIPyV DNA is predominantly found in respiratory tract samples of immunocompromised individuals and children suffering from respiratory diseases, but viral sequences have also been detected in brain, tonsil, lymphoid tissue studies, plasma, blood and faeces. Little is known about the sequence variation in the non-coding control region of KIPyV variants residing in different sites of the human body and whether specific strains dominate in certain parts of the world. In this study, we sequenced the non-coding control region (NCCR) of naturally occurring KIPyV variants in nasopharyngeal samples from patients with respiratory symptoms or infection and in blood from healthy donors in Norway. In total 86 sequences were obtained, 44 of which were identical to the original isolated Stockholm 60 variant. The remaining NCCRs contained one or several mutations, none of them previously reported. The same mutations were detected in NCCRs amplified from blood and nasopharyngeal samples. Some patients had different variants in their specimens. Transient transfection studies in HEK293 cells with a luciferase reporter plasmid demonstrated that some single mutations had a significant effect on the relative early and late promoter strength compared with the Stockholm 60 promoter. The effect of the NCCR mutations on viral replication and possible virulence properties remains to be established. INTRODUCTIONPolyomaviruses are non-enveloped viruses with a circular dsDNA genome of approximately 5000 bp. These viruses are common in birds and mammals, and recently the first complete fish polyomavirus genome has been published (Johne et al., 2011;Peretti et al., 2015). Their genome can †These authors contributed equally to this work.The GenBank/EMBL/DDBJ accession numbers for the sequences of the mutant NCCRs are KU564911-564952. ã 2016 The Authors Printed in Great Britain 1647Journal of General Virology (2016), 97, 1647-1657 DOI 10.1099 be divided into three functional regions: the early region, encoding regulatory proteins required for transcription and viral DNA replication; the late region, encoding the capsid proteins; and interspersed between these the non-coding control region (NCCR), encompassing the origin of replication and the promoters controlling transcription of the early and late genes, respectively (DeCaprio & Garcea, 2013). The first human polyomaviruses, BK and JC, were detected using histology or cytology followed by electron microscopy, and their existence was reported in 1971 (Gardner et al., 1971; Padgett et al., 1971). The development of new techniques such as high-throughput sequencing, rolling circle amplification and polymerase chain reaction with degenerate primers has led in recent years to the discovery of new polyomaviruses that can infect humans. KI polyomavirus, named after the researchers' instit...

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