High Expression of Polyomavirus-Encoded MicroRNAs in Progressive Multifocal Leukoencephalopathy and BK Polyomavirus-Associated Nephropathy Tissues, and Their Repressive Role in Virus Replication

Abstract

Background: Replication of JC polyomavirus (JCPyV, JCV) is associated with the pathogenesis of progressive multifocal leukoencephalopathy (PML). The JCPyV genome encodes a microRNA (miRNA) in the region encoding the large T antigen. This JCPyV-encoded miRNA (miR-J1) has been detected in tissue and cerebrospinal fluid samples of patients with PML. However, the localisation of the miRNA has rarely been reported. Methods: We detected viral miRNA by in situ hybridisation in polyomavirus-infected tissues. We measured the miR-J1 copy number with real-time RT PCR. Small RNAs were sequenced by next generation sequencing. Recombinant JCPyV DNA was transfected into cultured cells for functional analysis of the miRNA. Findings: We detected high expression of miR-J1 in the nuclei of JCPyV-infected cells in PML tissue samples by in situ hybridisation. In situ hybridisation also demonstrated the expression of BK polyomavirus (BKPyV, BKV)-encoded miRNA in lesions of BKPyV-associated nephropathy. Higher copy numbers of miR-J1 were detected in PML tissues than non-PML tissues by real-time PCR. Next generation sequencing showed that miR-J1-5p, a mature miRNA of miR-J1, was predominant in the lesions compared with miR-J1-3p, another mature miRNA. Deletion or mutation of miR-J1 in recombinant JCPyV promoted the production of JCPyV-encoded proteins in cells transfected with JCPyV DNA. Interpretation: We have demonstrated nuclear localisation of polyomavirus-encoded miRNA in tissue samples of polyomavirus-associated diseases. Our results suggest that polyomavirus-encoded miRNA may have a repressive role in viral replication in PML tissues. In situ hybridisation for viral miRNA may be a useful diagnostic tool for PML. Funding: AMED, JSPS, and MHLW, Japan. Declaration of Interest: The authors declare that they have no conflict of interest. Ethical Approval: All procedures performed in studies involving human tissues were in accordance with the ethical standards of the Institutional Review Board of the National Institute of Infectious Diseases (Approval No. 595) and with the 1964 Helsinki declaration and its later amendments or comparable ethical standards.