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

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.

JC Virus infected choroid plexus epithelial cells produce extracellular vesicles that infect glial cells independently of the virus attachment receptor

“…Once in the brain vesicles likely play a fundamental role in transmitting the infection to other glial cells and perhaps also to neurons in the case of granule cell neuronopathy, a rare complication of JCPyV infection of the brain [43]. Extracellular vesicles are also known to carry an abundance of regulatory molecules including transcription factors and microRNAs that influence the microenvironment of target tissues [44][45][46][47][48][49][50]. The contents of EV derived from JCPyV infected CPE cells, kidney tubule epithelial cells, and primary glial cells has yet to be examined in vitro or in vivo but such studies are likely to shed significant light on the pathogenic mechanisms of JCPyV induced disease.…”

Cellular and viral miRNA expression in polyomavirus BK infection

“…It is known that the bi‐directional expression of the archetype NCCR is critically modulated by Sp1 binding sites with high ( SP1‐4 ) and low affinity ( SP1‐2 ) binding sites in the early viral gene region and late viral gene region promoter, respectively. Accordingly, knockdown of Sp1 protein by siRNA is associated with a significant reduction in cellular and exosomal miRNA levels in BKPyV strains having an intact SP1‐4 binding site …”

BK polyomavirus infection promotes growth and aggressiveness in bladder cancer

“…A small amount of LTag however is not su cient to cause tumors. When BKPyV is activated in vivo, BKPyV triggers abnormally high expression of LTag in the host cell through various mechanism, eventually leading to cell transformation [18,19]. Based on our results, BKPyV infections did not have a lytic effect on bladder cancer cells.…”

“…Previous research pointed out that LTag and small tumor antigen(STag) of BKPyV can promote host cell transformation and immortalization, leading to enhanced cell proliferation capacity [18,19]. However, the role of BKPyV autoantigen expression in tumor cells has not been studied, and the biological characteristics of BKPyV-related tumors are unknown.…”