Reappraisal of progressive multifocal leukoencephalopathy due to simian virus 40

Progressive multifocal leukoencephalopathy in a patient with occult hypogammaglobulinemia experiencing bilateral visual impairment

INTRODUCTION

Progressive multifocal leukoencephalopathy (PML) is a rare, lethal, demyelinating disease classically seen in profoundly immunosuppressed individuals. It is caused by intracerebral infection by John Cunningham polyomavirus (JCV). We report a rare case of PML in a man with presumed immunocompetence at presentation experiencing bilateral painless visual impairment.

CASE DESCRIPTION

A 60-year-old man with a 3-week history of bilateral painless visual impairment attended our ophthalmology department. Unusually, he navigated around the room well and was able to read 4 of 13 Ishihara test plates in spite of a best-corrected visual acuity of counting fingers at 1 m bilaterally. Slit lamp examination, routine blood tests and optical coherence tomography (OCT) of the maculae and discs were unremarkable. Diffuse hyperintense white matter lesions on T2-weighted magnetic resonance imaging of the brain and detection of JCV within the parietal lobe tissue obtained by biopsy confirmed PML. Additional investigations identified an underlying hypogammaglobulinaemia, which may have initiated PML. He received intravenous immunoglobulin but passed away 2 months after diagnosis.

CONCLUSIONS

To our knowledge this case is one of only a handful worldwide to describe PML developing in a patient with presumed immunocompetence at presentation - there was no previous history of recurrent, chronic, or atypical infections. There has only been one other report of visual symptoms presenting as the primary complaint. The case illustrates the importance of ruling out organic, central nervous system pathology in patients presenting with visual loss and normal objective visual function tests such as slit lamp examination and OCT.

Unusual cause of fever, vision loss and super refractory status epilepticus in association with simian virus 40 (SV40)

We present a case of a 23-year-old man with history of fever followed by painless complete vision loss, with subsequent new-onset refractory status epilepticus (NORSE). He initially developed bilateral retinitis. A few days later, he started having focal seizures, and subsequently developed super-refractory status epilepticus, requiring anaesthetic agents. MRI brain revealed multifocal cortical and subcortical hyperintensities in occipital and temporoparietal regions without contrast enhancement. MRI repeated a month later showed new lesions with non-visualisation of some previous lesions. Finally, a brain biopsy was done which revealed presence of lymphocytic infiltrate with SV40 inclusions in oligodendrocyte. We propose the affliction of an atypical virus affecting the retina and brain grey and white matter, presenting with NORSE in our patient. Future similar cases and isolation of the virus may help in establishing the conclusive diagnosis.

Detection and typing of BKV, JCV, and SV40 by multiplex nested polymerase chain reaction

A multiplex nested polymerase chain reaction (PCR) method was developed for detecting and differentiating simultaneously the DNA of polyomaviruses JC, BK, and SV40 in a single tube. In the first amplification step the same set of primers was used to amplify a conserved DNA region of the large T antigen gene of JCV, BKV, and SV40. The second round was carried out using a set of primers designed to obtain products of different size for each related virus. Subsequently, the sensitivity of the multiplex nested PCR was maximized by optimizing parameters such as primer, magnesium, and dNTP concentrations. The sensitivity of the method ranged between 1 and 10 copies of the polyomavirus genome. The assay was then used for detecting polyomavirus DNA in urine, serum, and biopsy specimens from renal transplant recipients. Based on the results obtained, the multiplex nested PCR developed in our study represents a useful tool for supporting the diagnosis of polyomavirus infection and could be used for epidemiological purposes and to better define the role of polyomaviruses in human pathology.

JC virus genotyping using formalin-fixed, paraffin-embedded renal tissues

Recently genotyping of JC virus (JCV) DNA in renal tissue was reported to be useful to identify the geographic origin of unidentified cadavers. In the above study, autopsied tissue samples without storage or stored in a frozen state were used. This study examined JCV DNA sequence modifications caused by formalin-fixation, in an attempt to elucidate whether formalin-fixed, paraffin-embedded tissue samples can also be used to determine the genotypes of JCV DNA in the kidney. In four cases, a 610 bp typing region of the JCV genome was PCR-amplified from renal tissues stored for 1 year in three different states: frozen at -80 degrees C [Amaker, B.H., Chandler, F.W., Huey, L.O., Colwell, R.M., 1997. Molecular detection of JC virus in embalmed, formalin-fixed, paraffin-embedded brain tissue. J. Forensic Sci., 1157-1159], formalin-fixed, paraffin-embedded [Ault, G.S., Stoner, G.L., 1992. Two major types of JC virus defined in progressive multifocal leukoencephalopathy brain by early and late coding region DNA sequences. J. Gen. Virol. 73, 2669-2678], and soaked in 5% formalin [Baksh, F.K., Finkelstein, S.D., Swalskey, P.A., Stoner, G.L., Ryschkewitsch, C.F., Randhawa, P.R., 2001. Molecular genotyping of BK and JC virus in human polyomavirus-associated interstitial nephritis after renal transplantation. Am. J. Kidney Dis. 38 (2), 354-365]. The amplified fragments were cloned, and the resultant clones were sequenced. In frozen samples, single sequences ('original' sequences) were detected in all cases. In formalin-fixed, paraffin-embedded samples, not only the original sequences but also those with 1-6 base substitutions were detected. From formalin-soaked samples, the original sequences and those with 1-5 and 10-13 substitutions were detected. The genotyping of JCV DNA was not hampered by the presence of 1-6 substitutions, but a shift in JCV genotypes was observed in sequences with 10-13 substitutions. Thus, it was concluded that the genotypes of JCV DNA in the kidney can be determined only with specimens stored in a frozen state or formalin-fixed for a short time.

Comparison of PCR-southern hybridization and quantitative real-time PCR for the detection of JC and BK viral nucleotide sequences in urine and cerebrospinal fluid

The presence of the human polyomaviruses JCV and BKV in immunocompromised patients can lead to lethal diseases and conditions including progressive multifocal leukoencephalopathy (PML), interstitial nephritis, hemorrhagic cystitis, and kidney allograft rejection. Typically, detection of JCV and BKV in clinical samples has employed standard PCR amplification for viral nucleotide sequences, with subsequent confirmation for viral genome specificity of PCR products by southern blot hybridization. Here, we directly tested a validated PCR-southern protocol with a TaqMan real-time PCR protocol (Applied Biosystems) to assay clinical samples of urine and cerebrospinal fluid. We found equal specificity and sensitivity with both methods. However, real-time allowed for absolute viral-genome quantitation without the use of radionucleotides and was performed more rapidly, in as little as 24 h. Such advantages are important to consider in the effort to establish international standardization of controls for the detection of JCV and BKV, which would aid in screening confidence and the reliable assessment of anti-viral therapies.

Does SV40 infection contribute to the development of human cancers?

A large number of recent studies have reported the detection of simian virus 40 (SV40) nucleotide sequences in a number of unrelated human cancers which include paediatric and adult brain tumours, pleural mesotheliomas, bronchopulmonary carcinomas and osteosarcomas. Most of the data have been gathered by the use of PCR assays. These observations imply that SV40 is circulating in human communities by person-to-person transmission and that the virus is capable of wide dissemination in the infected individual. These claims must be regarded with skepticism for a variety of reasons. There are several inconsistencies in the reported data; for example, there is a wide variation (0-23%) in the frequency of SV40 sequences in normal tissues. The results of PCR assays have been difficult to confirm by less error-prone and independent assays and the relationship of the virus to the tumour cell is not characterised. The SV40 sequences reported from humans are essentially identical to those of wild-type SV40; it is difficult to conceive that a highly species-specific polyomavirus like SV40 would cross the species barrier, become a human infection, and acquire pathogenic potential for the new host without significant adaptive change in its genome. The available evidence, although not extensive, does not indicate that SV40 is circulating in human communities. It is premature to discuss or speculate on the potential role of SV40 in the development of human cancer until the presence of SV40 in cancers and in human communities is established unequivocally, the risk factors for SV40 infection are elucidated, and the effect of SV40 exposure on the development of specific cancers is examined in the context of other known risk factors for those cancers.

Multiplex polymerase chain reaction for the simultaneous detection and typing of polyomavirus JC, BK and SV40 DNA in clinical samples

A novel multiplex nested PCR (nPCR) method was developed for detecting and differentiating simultaneously the DNA of polyomaviruses JC, BK and SV40 in a single tube. In the first amplification step the same set of primers were used to amplify a conserved DNA region of the large T antigen gene of JCV, BKV and SV40. The second round of multiplex nPCR was carried out using a set of primers designed to render products of different size for each related virus. The thermocycling parameters and concentration of each reaction component were optimised systematically to achieve optimal specificity and sensitivity for the nPCR assay. The sensitivity of the method ranged between one and 10 copies of polyomavirus genome. Cerebrospinal fluid (CSF) was examined from AIDS patients with clinical and neuroradiological evidence of progressive multifocal leukoencephalopathy (PML) and CSF from AIDS patients with other neurological alterations. Urine specimens from bone marrow transplant recipients affected by haemorrhagic cystitis were also tested. The results obtained suggest that the assay is a good tool for supporting the diagnosis of polyomavirus infection and could be used for epidemiological purposes and in other studies in order to define better the role of polyomaviruses in human disease.