Human polyomavirus JC latency and reactivation status in blood of HIV-1-positive immunocompromised patients with and without progressive multifocal leukoencephalopathy

Antibodies reacting with JCPyV_VP2 _167-15mer as a novel serological marker for JC polyomavirus infection

Background

JC polyomavirus (JCPyV) is a widespread human polyomavirus that usually resides latently in its host, but can be reactivated under immune-compromised conditions potentially causing Progressive Multifocal Leukoencephalopathy (PML). Detection of antibodies against the major capsid protein VP1 currently is the main marker for assessment of infection with JCPyV.

Methods

Based on a peptide microarray, peptide JCPyV_VP2_167-15mer was selected and a peptide ELISA was developed for detection of antibodies directed against this peptide. Epitope mapping and computational modelling was performed to further characterize this peptide. In a cohort of 204 healthy subjects it was investigated whether antibodies against JCPyV_VP2_167-15mer were correlated with VP1 serology or urinary viral load.

Results

Epitope mapping of peptide JCPyV_VP2_167-15mer showed that the minimal epitope consisted of L₁₇₃PALTSQEI₁₈₁ with amino acids P₁₇₄, L₁₇₆ and E₁₈₀ being essential for antibody recognition. Computational analysis was used to predict that this epitope is located at an exposed domain of the VP2 capsid protein, readily accessible for immune recognition upon infection. No correlation could be observed with JCPyV VP1 antibody levels, or urinary viral load.

Conclusion

This work indicates that specific antibodies against JCPyV_VP2_167-15mer might be considered as a novel serological marker for infection with JCPyV.

Electronic supplementary material

The online version of this article (doi:10.1186/1743-422X-11-174) contains supplementary material, which is available to authorized users.

A peptide talk between JC virus and the human host: from silent infection to autoimmunity

Analysis of JC virus (JCV) polyprotein for peptide sharing with the human proteome reveals that the virus has hundreds of pentapeptide sequences in common with the human proteins. The datum is interesting in light of the fundamental role exerted by short amino acid sequences in protein-protein interactions and, consequently, in biochemical reactions and immune recognition. Searching for new approaches to understand the JCV infection scenarios, from the immunoevasion phenomenon underlying the viral asymptomatic stay in the human host to the (re)activation phase and associated pathogenic sequelae, the present study describes the diffuse pentapeptide communication network between JCV and the human host.

Progressive multifocal leukoencephalopathy and newer biological agents

Progressive multifocal leukoencephalopathy (PML) is a rare demyelinating disease of the brain due to a polyoma virus, JC virus. Despite the ubiquity of this virus, PML is rare and almost always seen in association with an underlying immunosuppressive condition. In the last 30 years, AIDS has been the most common predisposing factor. The observation of PML attending the use of certain monoclonal antibody therapies and other pharmacological agents has raised concerns about the safety profile of these agents, but has also provided a window into the pathogenesis of PML. Certain agents, such as the monoclonal antibodies natalizumab, an α4β1 and α4β7 integrin inhibitor, and efalizumab, an antibody directed against CD11a, appear to uniquely predispose to PML. Prior to their introduction for multiple sclerosis and Crohn's disease with respect to natalizumab, and psoriasis with respect to efalizumab, PML had never been observed with these disorders. PML occurring with other agents that currently carry US FDA-mandated 'black-box' warnings, such as rituximab, an antibody directed to CD20, or mycophenolate mofetil, a drug that inhibits T- and B-cell proliferation, typically occur in the background of underlying disorders that have already been identified as risks for PML. This review will focus on the available data regarding the risk for PML with monoclonal antibodies and other drugs. A biologically plausible explanation for the increased risk of PML will be proposed, as well as potential strategies for mitigating disease risk.

Human polyomavirus JC (JCV) infection of human B lymphocytes: a possible mechanism for JCV transmigration across the blood-brain barrier

It has been suggested that JC virus (JCV) might travel to the central nervous system in infected B cells. Moreover, recent data suggest the presence of JCV in bone marrow plasma cells. However, the evidence for infection and replication of JCV in B cells is unclear. To address this question, we infected Epstein-Barr virus-transformed B cells with JCV and found that the viral genome decreased >1000-fold from days 0 to 20 after infection, which concurred with the absence of viral early and late messenger RNA transcripts and proteins. However, immunofluorescent images of B cells infected with fluorescein isothiocyanate-conjugated JCV demonstrated that JCV enters the B cells, and DNase protection assay confirmed the presence of intact JCV virions inside the B cells. Moreover, JCV-infected B cells were able to transmit infection to naive glial cells. These data confirm that JCV nonproductively infects B cells and possibly uses them as a vehicle for transmigration across the blood-brain barrier.

Monoclonal antibodies and progressive multifocal leukoencephalopathy

Since their introduction, monoclonal antibodies have found an ever expanding role in the treatment of a wide number of disorders. However, the perturbation of the immune system that attends their use may also increase the risk for the development of disorders that arise in the setting of immunosuppressive conditions, such as, opportunistic infection and malignancy. In this paper, we address the association between some monoclonal antibodies and the development of a rare demyelinating disease of the brain, progressive multifocal leukoencephalopathy (PML). PML results from infection with a ubiquitous polyoma virus, JC virus, and typically occurs in the setting of impaired immunity, most commonly, AIDS. It was first recognized as a potential complication of monoclonal antibody therapy in patients with multiple sclerosis and Crohn disease being treated with natalizumab, an alpha 4 beta1 and alpha 4 beta 7 integrin inhibitor. Subsequently, efalizumab, a monoclonal antibody used in the treatment of psoriasis, was also demonstrated to be associated with PML. An increased risk has been suggested for rituximab, although most of the patients developing PML with that monoclonal antibody have been treated for B-cell disorders that predispose to the development of PML. Based on our current understanding of the biology of JC virus and the pathogenesis of PML, we propose an explanation for the increased risk for PML that is observed with natalizumab and certain other monoclonal antibodies.

Virus receptors and tropism

Polyomaviruses are small, tumorigenic, nonenveloped viruses that infect several different species. Interaction of these viruses with cell surface receptors represents the initial step during infection of host cells. This interaction can be a major determinant of viral host and tissue tropism. This chapter reviews what is currently known about the cellular receptors for each of five polyomavirus family members: Mouse polyomavirus (PyV), JC virus (JCV), BK virus (BKV), Lymphotropic papovavirus (LPV) and Simian virus 40 (SV40). These polyomaviruses serve to illustrate the enormous diversity of virus-cell surface interactions and allow us to closely evaluate the role of receptors in their life cycles. The contribution of other factors such as transcriptional regulators and signaling pathways are also summarized.

Primary central nervous system lymphoma expressing the human neurotropic polyomavirus, JC virus, genome

B lymphocytes are known as a potential site for latency and reactivation of the human neurotropic polyomavirus, JC virus (JCV). In light of recent studies on the oncogenicity of JCV and the transforming ability of the JCV early protein, T antigen, we investigated the association of JCV with B-cell lymphomas of the central nervous system. Examination of 27 well-characterized clinical specimens by gene amplification and immunohistochemistry revealed the presence of DNA sequences corresponding to the JCV early genome and the late Agnoprotein in 22 samples and the JCV late genome encoding the viral capsid proteins in 8 samples. Expression of T antigen and that of Agnoprotein by immunohistochemistry were each detected in six specimens. No evidence of the production of viral capsid proteins was observed, ruling out productive infection of JCV in the tumor cells. The results from laser capture microdissection verified the presence of JCV T-antigen sequences in tumor cells with positive immunoreactivity to antibodies against the viral proteins T antigen and Agnoprotein. Due to previous reports demonstrating an association of the Epstein-Barr virus (EBV) with transformation of B lymphocytes, EBV DNA sequences and the EBV transforming protein, latent membrane protein 1 (LMP1), were analyzed in parallel. EBV LMP1 DNA sequences were detected in 16 of 23 samples, and LMP1 expression was detected in 16 samples, 5 of which exhibited positive immunoreactivity to JCV proteins. Double labeling demonstrated coexpression of JCV T antigen and EBV LMP1 in the same cells. The detection of the JCV genome in large numbers of B-cell lymphomas and its coexistence with EBV suggest a potential role for JCV in the pathogenesis of primary CNS lymphoma.

Opportunistic infections of the CNS in patients with AIDS: diagnosis and management

The CNS is the second most commonly affected organ in patients with AIDS. Many opportunistic infections may involve the brain, but the four most frequent conditions are toxoplasmosis, progressive multifocal leukoencephalopathy (PML), cryptococcosis and cytomegalovirus infection. Although the incidence of these infections among patients with AIDS has decreased in the past years as a consequence of the introduction of highly active antiretroviral therapy (HAART), they remain a major cause of morbidity and mortality in this patient group. This article summarises the clinical manifestations, diagnostic procedures and management strategies for these four conditions. The clinical manifestations are nonspecific and depend on the type and location of the lesions. In clinical practice, the diagnosis of these entities is made with noninvasive methods. Imaging studies, especially magnetic resonance imaging, are very useful for the diagnosis of toxoplasmic encephalitis and PML, although their usefulness for the diagnosis of cryptococcal meningitis and cytomegalovirus infections is lower. The presence of multiple ring-enhancing lesions with surrounding oedema and mass effect is characteristic of toxoplasmosis. The response to antitoxoplasmic therapy, which is usually observed within the first 2 weeks, is also used for diagnostic purposes. Molecular methods applied to the CSF are essential for the diagnosis of PML and cytomegalovirus infections. In addition, the quantification of viral DNA of both JC virus (the causative agent of PML) and cytomegalovirus has prognostic implications and may serve to evaluate the response to therapy. Cryptococcosis may be easily diagnosed by CSF stains and cultures, as well as by the detection of the cryptococcal capsular polysaccharide antigen in the blood and, especially, the CSF. Effective treatments are available for toxoplasmosis and cryptococcosis, although adverse effects are common and some patients may not respond to therapy. In contrast, there is no specific treatment for PML, and the efficacy of anticytomegalovirus therapy is poor and the toxicity significant. HAART has improved the outcome of patients with AIDS who have infections of the CNS, and the initiation of this therapy is mandatory for all patients with such infections, particularly in those conditions for which effective therapy is not available. Lifelong secondary prophylaxis with agents for the opportunistic infections was necessary before the HAART era because the risk of recurrence was very high if only induction therapy was administered. However, today, the discontinuation of secondary prophylaxis in patients treated with HAART who have stably reached a certain immune reconstitution is possible.

Association of human polyomavirus JC with peripheral blood of immunoimpaired and healthy individuals

JC virus (JCV) infection is regularly asymptomatic in healthy individuals. In contrast, in immunocompromised individuals, highly activated virus replication may lead to PML. Peripheral blood cells (PBCs) are found to harbor JCV DNA in healthy and diseased individuals and it is discussed that they might be responsible for dissemination of the virus to the central nervous system (CNS) during persistence. To better understand the role of JCV DNA in PBCs for persistent infection and pathogenesis, the authors characterized the extent of JCV infection in Ficoll-gradient purified blood cells (peripheral blood mononuclear cells [PBMCs]) of healthy and human immunodeficiency virus type 1 (HIV-1)-infected individuals. Virus activation in PBMCs from healthy JCV-infected individuals was found at a rate of 0% to 38% at low polymerase chain reaction (PCR) sensitivity. In progressive multifocal leukoencephalopathy (PML) patients, a stronger signal was found, indicating increased virus activation. JCV DNA was regularly detected in T and B lymphocytes and in monocytes at low levels. However, granulocytes were shown to be the predominant reservoir of JCV DNA harboring high copy numbers. Although the overall distribution of viral genomes holds true for the population studied, in the individual, a markedly changed pattern of distribution can be found.

Semiquantitative detection of JCV-DNA in peripheral blood leukocytes from HIV-1-infected patients with or without progressive multifocal leukoencephalopathy

Progressive Multifocal Leukoencephalopathy (PML) is a severe and fatal demyelinating disease that occurs especially in HIV-infected patients. It has been suggested that JC virus (JCV) migrates in peripheral blood leukocytes from the kidney to the central nervous system where it initiates demyelination. To investigate the physiopathological role of the peripheral blood virus in the development of PML, the prevalence of JCV infection and the levels of JCV DNA load were evaluated in peripheral blood leukocytes or mononuclear cells of 10 AIDS patients at the time of onset of PML symptoms, and in 150 non-PML HIV-1-infected patients using a semiquantitative PCR and ELISA-hybridization assay. In PML-AIDS patients, 60% (6/10) were positive for JCV-DNA detection in peripheral blood cells compared with 26% (13/50) and 18% (18/100) positive for non-PML HIV-infected control patients with CD4+ T lymphocyte counts below and above 200.10(6) /l, respectively (60 vs. 26%, P = 0.06; 60 vs. 18%; P = 0.007). The prevalence of JCV infection in the peripheral blood cells taken from controls appeared to be independent of the CDC stage of infection and CD4+ T lymphocyte counts. The predictive positive value of a positive JCV DNA PCR in peripheral blood cells for the diagnosis of PML in an HIV-infected patient was 16% whereas the predictive negative value was 96%. The levels of circulating JCV DNA load, ranging from 1.69 to 2.53 log of copies per 10(6) cells, did not differ between patients at time of PML symptoms onset and controls, and appeared to be independent of the clinical and the biological status in control patients. The findings do not indicate any significant JCV genomic replication activity in peripheral blood cells at the onset of PML disease, and suggest that JCV replication markers in the systemic compartment would not be valuable for predicting the development of PML in AIDS patients.