Studies on human polyomavirus infection in immunosuppressed patients with polyoma related tumors

Abstract

Polyomaviruses are potentially oncogenic viruses, found in humans, in other mammals and in birds all over the world. The polyomaviruses that have been observed in humans are BK virus (BKV) and JC virus (JCV) as well as the primate polyomavirus Simian Virus 40 (SV40). BKV and JCV persistent latent in humans, but are not believed do not cause any disease or symptoms in immunocompetent individuals. However, in immunosuppressed individuals, e.g in bone marrow transplanted (BMT) patients BKV has been reported to be associated with hemorrhagic cystitis (HC), and in HIV positive patients JCV has been shown to cause progressive multifocal leukoencephalopathy (PML). SV40 is believed to have been transferred to humans via contaminated polio vaccine 195561, and recent studies have detected fragments of SV40 DNA in malignant mesotheliomas (MM), brain tumors and osteosarcomas. However, the reported frequency varies widely between different studies and countries. 'Me aim of the present study was to further investigate human polyomavirus infections in immunosuppressed patients and in patients with polyoma virus related tumors.

In BMT patients with late onset HC, BKV is excreted in the urine, but all BMT patients with BK viruria do not develop HC. To investigate if primary BKV infection transmitted from donor to recipient during BMT could cause HC we investigated anti BKV serum titers in BMT recipients and their donors. We also sequenced the non coding control region (NCCR) and the VP1 region of BKV from BMT patients to search for mutations correlated to the development of HC. Primary BKV infection was not the major cause of HC in BMT patients since all patients had anti BKV antibody titers before BMT. However, after BMT significantly more patients with HC had serological changes compared to patients without HC. BKV with C to G mutations in the NCCR Sp1 binding site was significantly over represented in BMT patients with HC. However, when we by Real Time PCR investigated if these mutations resulted in a higher BKV load in the urine of affected patients, we found that this was not the case.

To study if human polyomavirus reactivation was related to graft cold ischemia time and if this could cause graft rejections in renal transplant (RTX) patients, we analyzed urine samples by PCR from RTX patients for presence of BKV or JCV and in parallel we examined their files for graft rejection. Reactivation of BKV or JCV was not correlated to the length of the cold ischemia time or to complications after RTX, such as rejection.

JCV can be detected by PCR in the cerebrospinal fluid (CSF) of patients with PML. To investigate if JCV is present in CSF during other central nervous system (CNS) infections or in Multiple Sclerosis (MS) patients, we analyzed CSF samples by PCR from patients with other vital CNS infections and MS. JCV was not detected by PCR in CSF from patients with HSV-1 encephalitis, enteroviral meningitis, nonenteroviral meningitis or during MS. Thus, detection of JCV by PCR in CSF is indicative for PML.

In order to investigate if SV40 or human polyomaviruses were present in Swedish malignant mesotheliomas (MM), and possibly related to the distribution of early batches of SV40 contaminated polio vaccine, we analyzed Swedish MM samples for SV40 by PCR. SV40 was present in only 10% of the Swedish MM (from three men hom 1905-1953), which was less than that reported, 40-69% in Italy and the USA. This indicates that SV40 contaminated polio vaccine not was distributed widely in Sweden even before 1958.