Detection of reactivation and size variation in the regulatory region of JC virus in brain tissue

A prospective study of renal transplant recipients reveals an absence of primary JC polyomavirus infections

BACKGROUND

Both JC polyomavirus (JCPyV) and BK polyomavirus (BKPyV) are acquired at an early age. JCPyV causes progressive multifocal leukoencephalopathy and has been described in association with nephropathy.

OBJECTIVES

Urine and plasma samples from renal transplant recipients (RTRs) were examined for JCPyV to determine its involvement in causing infection and disease.

STUDY DESIGN

JCPyV testing was performed on 112 RTRs included in a randomised controlled study of steroid-sparing immunosuppressive regimens [1]. Urine and EDTA blood samples were collected pre- and post-transplantation and analysed for JCPyV using real-time PCR and sequencing to determine genotype and viral variation. Donor and recipient IgG antibody status to JCPyV was also determined.

RESULTS

Overall, 13.3% of RTRs were positive for JCPyV of which one patient developed viraemia without viruria. JCPyV DNA was detected early following transplantation (defined as five days post transplantation) from recipients with donors that were positive for JCPyV IgG antibodies. No dual cases of JCPyV and BKPyV were observed. One patient sample had sequence duplication in the non-coding control region.

CONCLUSIONS

Like BKPyV, JCPyV tends to occur early post transplantation but did not result in sustained viraemia. There was no deterioration of renal function in patients positive for JCPyV. As with other viruses, JCPyV donor serostatus was a risk factor for detection of JCPyV DNA. JCPyV appears to protect individuals from BKPyV infection, as recipients were twice as likely to develop BKPyV with a negative JCPyV donor.

Viral induced demyelination

Viral induced demyelination, in both humans and rodent models, has provided unique insights into the cell biology of oligodendroglia, their complex cell-cell interactions and mechanisms of myelin destruction. They illustrate mechanisms of viral persistence, including latent infections in which no infectious virus is readily evident, virus reactivation and viral-induced tissue damage. These studies have also provided excellent paradigms to study the interactions between the immune system and the central nervous system (CNS). Although of interest in their own right, an understanding of the diverse mechanisms used by viruses to induce demyelination may shed light into the etiology and pathogenesis of the common demyelinating disorder multiple sclerosis (MS). This notion is supported by the persistent view that a viral infection acquired during adolescence might initiate MS after a long period of quiescence. Demyelination in both humans and rodents can be initiated by infection with a diverse group of enveloped and non-enveloped RNA and DNA viruses (Table 1). The mechanisms that ultimately result in the loss of CNS myelin appear to be equally diverse as the etiological agents capable of causing diseases which result in demyelination. Although demyelination can be a secondary result of axonal loss, in many examples of viral induced demyelination, myelin loss is primary and associated with axonal sparing. This suggests that demyelination induced by viral infections can result from: 1) a direct viral infection of oligodendroglia resulting in cell death with degeneration of myelin and its subsequent removal; 2) a persistent viral infection, in the presence or absence of infectious virus, resulting in the loss of normal cellular homeostasis and subsequent oligodendroglial death; 3) a vigorous virus-specific inflammatory response wherein the virus replicates in a cell type other than oligodendroglia, but cytokines and other immune mediators directly damage the oligodendroglia or the myelin sheath; or 4) infection initiates activation of an immune response specific for either oligodendroglia or myelin components. Virus-induced inflammation may be associated with the processing of myelin or oligodendroglial components and their presentation to the host's own T cell compartment. Alternatively, antigenic epitopes derived from the viral proteins may exhibit sufficient homology to host components that the immune response to the virus activates autoreactive T cells, i.e. molecular mimicry. Although it is not clear that each of these potential mechanisms participates in the pathogenesis of human demyelinating disease, analysis of the diverse demyelinating viral infections of both humans and rodents provides examples of many of these potential mechanisms.