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Viruses 2018, 10(9), 466; https://doi.org/10.3390/v10090466

BK Polyomavirus MicroRNA Levels in Exosomes Are Modulated by Non-Coding Control Region Activity and Down-Regulate Viral Replication When Delivered to Non-Infected Cells Prior to Infection

1
Department of Experimental and Clinical Medicine, University of Florence, I-50134 Florence, Italy
2
Transplantation & Clinical Virology, Department Biomedicine (Haus Petersplatz), University of Basel, CH-4003 Basel, Switzerland
3
Department of Biomedical, Surgical and Dental Sciences, University of Milan, I-20100 Milano, Italy
4
Infectious Diseases & Hospital Epidemiology, University Hospital Basel, CH-4003 Basel, Switzerland
Both authors contributed equally to this study.
*
Authors to whom correspondence should be addressed.
Received: 30 May 2018 / Accepted: 29 August 2018 / Published: 30 August 2018
(This article belongs to the Section Animal Viruses)
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Abstract

In immunosuppressed patients, BKPyV-variants emerge carrying rearranged non-coding control-regions (rr-NCCRs) that increase early viral gene region (EVGR) expression and replication capacity. BKPyV also encodes microRNAs, which have been reported to downregulate EVGR-encoded large T-antigen transcripts, to decrease viral replication in infected cells and to be secreted in exosomes. To investigate the interplay of NCCR and microRNAs, we compared archetype- and rr-NCCR-BKPyV infection in cell culture. We found that laboratory and clinical rr-NCCR-BKPyV-strains show higher replication rates but significantly lower microRNA levels than archetype virus intracellularly and in exosomes. To investigate whether rr-NCCR or increased EVGR activity modulated microRNA levels, we examined the (sp1-4)NCCR-BKPyV, which has an archetype NCCR-architecture but shows increased EVGR expression due to point mutations inactivating one Sp1 binding site. We found that microRNA levels following (sp1-4)NCCR-BKPyV infection were as low as in rr-NCCR-variants. Thus, NCCR rearrangements are not required for lower miRNA levels. Accordingly, Sp1 siRNA knock-down decreased microRNA levels in archetype BKPyV infection but had no effect on (sp1-4)- or rr-NCCR-BKPyV. However, rr-NCCR-BKPyV replication was downregulated by exosome preparations carrying BKPyV-microRNA prior to infection. To explore the potential relevance in humans, urine samples from 12 natalizumab-treated multiple sclerosis patients were analysed. In 7 patients, rr-NCCR-BKPyV were detected showing high urine BKPyV loads but low microRNAs levels, whereas the opposite was seen in 5 patients with archetype BKPyV. We discuss the results in a dynamic model of BKPyV replication according to NCCR activity and exosome regulation, which integrates immune selection pressure, spread to new host cells and rr-NCCR emergence. View Full-Text
Keywords: polyomavirus; non-coding control region; microRNA; exosomes; persistence; immunosuppression; BK virus polyomavirus; non-coding control region; microRNA; exosomes; persistence; immunosuppression; BK virus
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Martelli, F.; Wu, Z.; Delbue, S.; Weissbach, F.H.; Giulioli, M.C.; Ferrante, P.; Hirsch, H.H.; Giannecchini, S. BK Polyomavirus MicroRNA Levels in Exosomes Are Modulated by Non-Coding Control Region Activity and Down-Regulate Viral Replication When Delivered to Non-Infected Cells Prior to Infection. Viruses 2018, 10, 466.

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