In this thesis, the role of genetic variation of human JC and BK polyomaviruses (JCPyV, BKPyV) in the development of severe polyomavirus-associated diseases was investigated by characterizing JCPyV and BKPyV strains present in urine, plasma, and cerebrospinal fluid samples using next-generation sequencing. These viruses are established human pathogens causing clinical manifestations almost exclusively in immunosuppressed patients. Immunosuppression allows lytic JCPyV infection in the brain, which is a hallmark of severe brain disease, progressive multifocal leukoencephalopathy (PML). Lytic BKPyV infection in the kidneys may result in the development of BKPyV-associated nephropathy (BKPVAN). Rare cases of nephropathy associated with JCPyV (JCPVAN) have been reported as well. No treatment is currently available leaving reduction of immunosuppression as the only therapy option. Mutations within the viral genome affect pathogenicity of JCPyV, and the same has been suggested for BKPyV. Although PML is always associated with mutated neurotropic JCPyV strains, the exact content of mutations, as well as where, when, and how neurotropic strains develop is unknown. Mutations are frequently seen in BKPVAN-associated BKPyV strains as well, but their association with the pathogenesis of BKPVAN remains elusive. First, we performed single-molecule real-time sequencing of complete JCPyV genomes from three PML patients and characterized all mutations within the viral regulatory region and the major capsid protein of each individual virus strain. We identified three distinct neurotropic JCPyV strains from cerebrospinal fluid of one PML patient. Mutations in the viral regulatory region and in the major capsid protein gene seem necessary for PML pathogenesis. Moreover, the presence of an archetype-like strain in one patient indicates that even minor mutations may be sufficient for the development of PML. Second, we were the first to show the predominance of archetype JCPyV in the urine of twenty stable kidney transplant patients and one patient with extremely rare JCPVAN. Contrary to PML, mutations within the JCPyV genome seem not necessary for the development of JCPVAN, but rather patient-specific factors, such as cell-mediated immunity, may play a role in the pathogenesis of JCPVAN. In the third and fourth studies, we characterized BKPyV regulatory regions from the plasma and urine samples of kidney transplant patients with or without histologically confirmed BKPVAN. Archetype BKPyV predominated in all but one patient but also very small populations of mutated BKPyV strains were detected. Interestingly, viral microRNA expression, as measured in the plasma of nine presumptive and biopsy-confirmed BKPVAN patients, was increased in the presence of mutated strains. Similar to JCPVAN, archetype strains may be sufficient for the development of BKPVAN, but even low amounts of mutated strains may affect pathogenicity of BKPyV by regulating the expression of viral microRNAs. This thesis contributes to the understanding of the role of genetic variation of JCPyV and BKPyV in the pathogenesis of PML, JCPVAN, and BKPVAN. Viral mutations seem necessary for the development of PML in the brain, but not for BKPVAN and JCPVAN in the kidney where other factors may play a role. The results help improving the diagnostic methods for the prognosis and prevention of these severe diseases.
|Tila||Julkaistu - 2019|
|OKM-julkaisutyyppi||G5 Tohtorinväitöskirja (artikkeli)|
- 3111 Biolääketieteet
- 1183 Kasvibiologia, mikrobiologia, virologia