Reactivation of human herpesvirus-6 in natalizumab treated multiple sclerosis patients

The complement system in neurodegenerative and inflammatory diseases of the central nervous system

Neurodegenerative and neuroinflammatory diseases, including Alzheimer's disease, Parkinson's disease, and multiple sclerosis, affect millions of people globally. As aging is a major risk factor for neurodegenerative diseases, the continuous increase in the elderly population across Western societies is also associated with a rising prevalence of these debilitating conditions. The complement system, a crucial component of the innate immune response, has gained increasing attention for its multifaceted involvement in the normal development of the central nervous system (CNS) and the brain but also as a pathogenic driver in several neuroinflammatory disease states. Although complement is generally understood as a liver-derived and blood or interstitial fluid operative system protecting against bloodborne pathogens or threats, recent research, particularly on the role of complement in the healthy and diseased CNS, has demonstrated the importance of locally produced and activated complement components. Here, we provide a succinct overview over the known beneficial and pathological roles of complement in the CNS with focus on local sources of complement, including a discussion on the potential importance of the recently discovered intracellularly active complement system for CNS biology and on infection-triggered neurodegeneration.

Vaccine-associated measles in a patient treated with natalizumab: a case report

Background

Safety of live vaccines in patients treated with immunosuppressive therapies is not well known, resulting in contradictory vaccination recommendations. We describe here the first case of vaccine-associated measles in a patient on natalizumab treatment.

Case presentation

A young female patient with relapsing-remitting multiple sclerosis on natalizumab treatment received the live attenuated measles, mumps, and rubella vaccine in preparation for a change in her treatment in favour of fingolimod, with established immunosuppressive qualities. Seven days after receiving the vaccine, our patient experienced diffuse muscle pain, fatigue, and thereafter developed a fever and then an erythematous maculopapular rash, compatible with vaccine associated measles. This was later confirmed by a positive measles RT-PCR throat swab. The patient’s symptoms resolved without any sequelae.

Conclusion

In this case report we review the immunosuppressive qualities of natalizumab and the evidence in favour and against live vaccines in patients on this treatment. Our findings reveal the insufficient understanding of the immunosuppressive effects of new immunomodulators, and thus of the safety of live vaccines in patients on such medications. While this case triggers precaution, there is insufficient evidence to conclude that natalizumab treatment could favor the onset of vaccine-associated measles.

A case of recurrent progressive multifocal leukoencephalopathy after human stem cell transplant, with detection of John Cunningham virus and human herpesvirus 6 on cerebrospinal fluid, treated with Mirtazapine, Olanzapine and Foscarnet

We reported the case of a John Cunningham virus (JCV) and human herpesvirus 6 (HHV-6) mediated progressive multifocal leukoencephalopathy (PML) after human stem cell transplant, reactivated 6 months later in absence of immunosuppressive therapy, successfully treated with anti-5HT2A receptors agents and antiviral therapy. Few cases of JCV and HHV-6 coinfection associated PML are described in literature and the role of HHV-6 in the pathogenesis and prognosis of PML is not completely clear. Our case suggests that, in a possible PML, the research of HHV-6 and JCV should be always performed on cerebrospinal fluid (CSF) and on blood samples and in case of detection of HHV-6 DNA a chromosomally integrated human herpesvirus 6(ciHHV-6) should be excluded. Furthermore we recommend to start an appropriate therapy with antiviral and anti-5HT2A receptors agents in case of possible PML due to JCV and HHV-6 coinfection.

Multiple sclerosis: an example of pathogenic viral interaction?

A hypothesis is formulated on viral interaction between HHV-6A and EBV as a pathogenic mechanism in Multiple Sclerosis (MS). Evidence of molecular and genetic mechanisms suggests a link between HHV-6A infection and EBV activation in the brain of MS patients leading to intrathecal B-cell transformation. Consequent T-cell immune response against the EBV-infected cells is postulated as a pathogenic basis for inflammatory lesion formation in the brain of susceptible individuals. A further link between HHV-6A and EBV involves their induction of expression of the human endogenous retrovirus HERV-K18-encoded superantigen. Such virally induced T-cell responses might secondarily also lead to local autoimmune phenomena. Finally, research recommendations are formulated for substantiating the hypothesis on several levels: epidemiologically, genetically, and viral expression in the brain.

Roseolovirus-associated encephalitis in immunocompetent and immunocompromised individuals

The roseoloviruses, human herpesvirus (HHV)-6A, HHV-6B, and HHV-7, can cause severe encephalitis or encephalopathy. In immunocompetent children, primary HHV-6B infection is occasionally accompanied by diverse clinical forms of encephalitis. Roseolovirus coinfections with heterologous viruses and delayed primary HHV-7 infection in immunocompetent adults result in very severe neurological and generalized symptoms. Recovery from neurological sequelae is slow and sometimes incomplete. In immunocompromised patients with underlying hematological malignancies and transplantation, frequent single or simultaneous reactivation of roseoloviruses elicit severe, lethal organ dysfunctions, including damages in the limbic system, brain stem, and hippocampus. Most cases have been due to HHV-6B with HHV-6A accounting for 2-3%. The most severe manifestation of HHV-6B reactivation is post-transplantation limbic encephalitis. Seizures, cognitive problems, and abnormal EEG are common. Major risk factors for HHV-6B-associated encephalitis include unrelated cord blood cell transplantation and repeated hematopoietic stem cell transplantation. Rare genetic disorders, male gender, certain HLA constellation, and immune tolerance to replicating HHV-6 in persons carrying chromosomally integrated HHV-6 might also predispose an individual to roseolovirus-associated brain damage. At this time, little is known about the risk factors for HHV-7-associated encephalitis. Intrathecal glial cell destruction due to virus replication, overexpression of proinflammatory cytokines, and viral mimicry of chemokines all contribute to brain dysfunction. High virus load in the cerebrospinal fluid, hippocampal astrogliosis, and viral protein expression in HHV-6B-associated cases and multiple microscopic neuronal degeneration in HHV-7-associated cases are typical laboratory findings. Early empirical therapy with ganciclovir or foscarnet might save the life of a patient with roseolovirus-associated encephalitis.

Persistent infections, immune-senescence and Alzheimer's disease

Alzheimer's disease (AD) is a progressive neurodegenerative disorder and the most common cause of dementia. Classical hallmarks of AD such as amyloid deposition and neurofibrillary tangles do not completely explain AD pathogenesis. Recent investigations proposed Aβ peptide as an anti-microbial factor. Our previous works suggested that the concomitant presence of single nucleotide polymorphisms (SNPs) from AD genetic studies might impair antiviral defenses and increase the individual susceptibility to herpes virus infection. Viruses of herpes family by inducing frequent cycles of reactivation and latency constantly challenge the immune response and drive the accumulation of memory T cells. However, the immune system is not able to completely eradicate these viruses. The continuous antigen stimulation activates chronic inflammatory responses that may progressively induce neurodegenerative mechanisms in genetically susceptible elderly. The aim of this paper is to suggest new perspectives in clinical pathogenesis of AD with potential prevention and new medical treatment of the age associated cognitive decline.

Herpes Simplex Virus Type 1 and Other Pathogens are Key Causative Factors in Sporadic Alzheimer's Disease

This review focuses on research in epidemiology, neuropathology, molecular biology, and genetics regarding the hypothesis that pathogens interact with susceptibility genes and are causative in sporadic Alzheimer's disease (AD). Sporadic AD is a complex multifactorial neurodegenerative disease with evidence indicating coexisting multi-pathogen and inflammatory etiologies. There are significant associations between AD and various pathogens, including Herpes simplex virus type 1 (HSV-1), Cytomegalovirus, and other Herpesviridae, Chlamydophila pneumoniae, spirochetes, Helicobacter pylori, and various periodontal pathogens. These pathogens are able to evade destruction by the host immune system, leading to persistent infection. Bacterial and viral DNA and RNA and bacterial ligands increase the expression of pro-inflammatory molecules and activate the innate and adaptive immune systems. Evidence demonstrates that pathogens directly and indirectly induce AD pathology, including amyloid-β (Aβ) accumulation, phosphorylation of tau protein, neuronal injury, and apoptosis. Chronic brain infection with HSV-1, Chlamydophila pneumoniae, and spirochetes results in complex processes that interact to cause a vicious cycle of uncontrolled neuroinflammation and neurodegeneration. Infections such as Cytomegalovirus, Helicobacter pylori, and periodontal pathogens induce production of systemic pro-inflammatory cytokines that may cross the blood-brain barrier to promote neurodegeneration. Pathogen-induced inflammation and central nervous system accumulation of Aβ damages the blood-brain barrier, which contributes to the pathophysiology of AD. Apolipoprotein E4 (ApoE4) enhances brain infiltration by pathogens including HSV-1 and Chlamydophila pneumoniae. ApoE4 is also associated with an increased pro-inflammatory response by the immune system. Potential antimicrobial treatments for AD are discussed, including the rationale for antiviral and antibiotic clinical trials.

Classification of HHV-6A and HHV-6B as distinct viruses

Shortly after the discovery of human herpesvirus 6 (HHV-6), two distinct variants, HHV-6A and HHV-6B, were identified. In 2012, the International Committee on Taxonomy of Viruses (ICTV) classified HHV-6A and HHV-6B as separate viruses. This review outlines several of the documented epidemiological, biological, and immunological distinctions between HHV-6A and HHV-6B, which support the ICTV classification. The utilization of virus-specific clinical and laboratory assays for distinguishing HHV-6A and HHV-6B is now required for further classification. For clarity in biological and clinical distinctions between HHV-6A and HHV-6B, scientists and physicians are herein urged, where possible, to differentiate carefully between HHV-6A and HHV-6B in all future publications.

Long-term safety and efficacy of natalizumab in relapsing-remitting multiple sclerosis: impact on quality of life

Natalizumab was the first monoclonal antibody to be approved for the treatment of relapsing-remitting multiple sclerosis (RRMS) based on its short-term efficacy and overall tolerability. However, the incidence of treatment-associated progressive multifocal leukoencephalopathy (PML), an infection of the brain caused by the John Cunningham virus, jeopardized this efficacious treatment from the beginning. Eight years after licensing of natalizumab, long-term studies confirm the considerable and sustained efficacy of natalizumab, although the PML complication still threatens one of the most successful treatments available for RRMS. During these years, considerable progress has been made in identification of risk factors that allow more effective management of PML risk. In addition, long-term studies to define better when to start or stop treatment and to optimize treatment strategies after cessation of natalizumab are ongoing, and hopefully will improve management and will allow natalizumab to remain as a valuable therapeutic option for patients with highly active RRMS.

Novel marmoset (Callithrix jacchus) model of human Herpesvirus 6A and 6B infections: immunologic, virologic and radiologic characterization

Human Herpesvirus 6 (HHV-6) is a ubiquitous virus with an estimated seroprevalence of 95% in the adult population. HHV-6 is associated with several neurologic disorders, including multiple sclerosis, an inflammatory demyelinating disease affecting the CNS. Animal models of HHV-6 infection would help clarify its role in human disease but have been slow to develop because rodents lack CD46, the receptor for cellular entry. Therefore, we investigated the effects of HHV-6 infections in a non-human primate, the common marmoset Callithrix jacchus. We inoculated a total of 12 marmosets with HHV-6A and HHV-6B intravenously and HHV-6A intranasally. Animals were monitored for 25 weeks post-inoculation clinically, immunologically and by MRI. Marmosets inoculated with HHV-6A intravenously exhibited neurologic symptoms and generated virus-specific antibody responses, while those inoculated intravenously with HHV-6B were asymptomatic and generated comparatively lower antibody responses. Viral DNA was detected at a low frequency in paraffin-embedded CNS tissue of a subset of marmosets inoculated with HHV-6A and HHV-6B intravenously. When different routes of HHV-6A inoculation were compared, intravenous inoculation resulted in virus-specific antibody responses and infrequent detection of viral DNA in the periphery, while intranasal inoculation resulted in negligible virus-specific antibody responses and frequent detection of viral DNA in the periphery. Moreover, marmosets inoculated with HHV-6A intravenously exhibited neurologic symptoms, while marmosets inoculated with HHV-6A intranasally were asymptomatic. We demonstrate that a marmoset model of HHV-6 infection can serve to further define the contribution of this ubiquitous virus to human neurologic disorders.

Monitoring of active human herpes virus 6 infection in Iranian patients with different subtypes of multiple sclerosis

Background. Recently, it has been suggested that human herpes virus 6 (HHV6) may play a role in the pathogenesis of multiple sclerosis (MS). Our purpose is to determine the incidence of reactivated HHV6 in MS patients. Methods. Viral sequence analyzed by qPCR in the peripheral blood mononuclear cells (PBMCs), serum, and saliva samples of different subtypes of MS patients (n = 78) and healthy controls (n = 123). HHV6 IgG and IgM antibody levels measured by ELISA technique in the plasma samples of both groups. Likewise, cerebrospinal fluid (CSF) samples of some MS patients (n = 38) were analyzed for viral sequence. Results. Results demonstrate increased levels of anti-HHV6-IgG (78.2% versus 76.4% in controls; P = NS), and IgM (34.6% versus 6.5% in controls; P < 0.05) in MS patients. Furthermore, RRMS and SPMS patients showed relatively higher anti-HHV6 IgG and IgM compared to PPMS (P < 0.001). Moreover, load of cell-free viral DNA was higher in RRMS and SPMS patients and detected in 60.2% (47/78) of MS patients, compared with 14.6% (18/123) of healthy controls (P < 0.001). Moreover, load of cell-free viral DNA was higher in RRMS and SPMS patients and detected in 60.2% (47/78) of MS patients, compared with 14.6% (18/123) of healthy controls (P < 0.001). Conclusions. The results extend the observation of an increased frequency of systemic reactivated HHV6 infection in MS patients with developed stages of disease.

Concordance of preclinical and clinical pharmacology and toxicology of therapeutic monoclonal antibodies and fusion proteins: cell surface targets

Monoclonal antibodies (mAbs) and fusion proteins directed towards cell surface targets make an important contribution to the treatment of disease. The purpose of this review was to correlate the clinical and preclinical data on the 15 currently approved mAbs and fusion proteins targeted to the cell surface. The principal sources used to gather data were: the peer reviewed Literature; European Medicines Agency 'Scientific Discussions'; and the US Food and Drug Administration 'Pharmacology/Toxicology Reviews' and package inserts (United States Prescribing Information). Data on the 15 approved biopharmaceuticals were included: abatacept; abciximab; alefacept; alemtuzumab; basiliximab; cetuximab; daclizumab; efalizumab; ipilimumab; muromonab; natalizumab; panitumumab; rituximab; tocilizumab; and trastuzumab. For statistical analysis of concordance, data from these 15 were combined with data on the approved mAbs and fusion proteins directed towards soluble targets. Good concordance with human pharmacodynamics was found for mice receiving surrogates or non-human primates (NHPs) receiving the human pharmaceutical. In contrast, there was poor concordance for human pharmacodynamics in genetically deficient mice and for human adverse effects in all three test systems. No evidence that NHPs have superior predictive value was found.

Pre-existing T- and B-cell defects in one progressive multifocal leukoencephalopathy patient

Progressive multifocal leukoencephalopathy (PML) usually occurs in patients with severe immunosuppression, hematological malignancies, chronic inflammatory conditions or receiving organ transplant. Recently, PML has also been observed in patients treated with monoclonal antibodies. By taking advantage of the availability of samples from a multiple sclerosis (MS) patient treated with natalizumab, the antibody anti-α4 integrin, who developed PML and was monitored starting before therapy initiation, we investigated the fate of T and B lymphocytes in the onset of PML. Real-time PCR was used to measure new T- and B-cell production by means of T-cell receptor excision circle (TREC) and K-deleting recombination excision circle (KREC) analysis and to quantify transcripts for CD34, terminal-deoxynucleotidyltransferase, and V pre-B lymphocyte gene 1. T- and B-cell subsets and T-cell heterogeneity were measured by flow cytometry and spectratyping. The data were compared to those of untreated and natalizumab-treated MS patients and healthy donors. Before therapy, a patient who developed PML had a low TREC and KREC number; TRECs remained low, while KRECs and pre-B lymphocyte gene 1 transcripts peaked at 6 months of therapy and then decreased at PML diagnosis. Flow cytometry confirmed the deficient number of newly produced T lymphocytes, counterbalanced by an increase in TEMRA cells. The percentage of naive B cells increased by approximately 70% after 6 months of therapy, but B lymphocyte number remained low for the entire treatment period. T-cell heterogeneity and immunoglobulins were reduced.

Although performed in a single patient, all results showed that an immune deficit, together with an increase in newly produced B cells a few months after therapy initiation, may predispose the patient to PML. These findings indicate the TREC/KREC assay is a potential tool to identify patients at risk of developing PML and may provide insights into the immunological involvement of monoclonal antibody-associated therapies.

Herpes encephalitis during natalizumab treatment in multiple sclerosis

In this case report we describe the first non-fatal herpes simplex virus encephalitis (HSE) case with natalizumab for multiple sclerosis (MS). A 36-year-old woman, previously treated with immunomodulatory and immunosuppressive drugs for MS, developed acute encephalitis after 6 monthly natalizumab perfusions. Brain imaging demonstrated suggestive bi-temporal lesions. Herpes simplex virus type-1 DNA was detected in cerebrospinal fluid. The patient improved gradually after a 21-day course of intravenous acyclovir, but neuropsychiatric changes remained 5 months later. Our non-fatal case of HSE and other reported cases of herpes infections provide evidence of an increased risk with natalizumab and point to the need for clinicians to maintain awareness.

Functional energetics of CD4+-cellular immunity in monoclonal antibody-associated progressive multifocal leukoencephalopathy in autoimmune disorders

BACKGROUND

Progressive multifocal leukoencephalopathy (PML) is an opportunistic central nervous system- (CNS-) infection that typically occurs in a subset of immunocompromised individuals. An increasing incidence of PML has recently been reported in patients receiving monoclonal antibody (mAb) therapy for the treatment of autoimmune diseases, particularly those treated with natalizumab, efalizumab and rituximab. Intracellular CD4(+)-ATP-concentration (iATP) functionally reflects cellular immunocompetence and inversely correlates with risk of infections during immunosuppressive therapy. We investigated whether iATP may assist in individualized risk stratification for opportunistic infections during mAb-treatment.

METHODOLOGY/PRINCIPAL FINDINGS

iATP in PHA-stimulated, immunoselected CD4(+)-cells was analyzed using an FDA-approved assay. iATP of mAb-associated PML (natalizumab (n = 8), rituximab (n = 2), efalizumab (n = 1)), or other cases of opportunistic CNS-infections (HIV-associated PML (n = 2), spontaneous PML, PML in a psoriasis patient under fumaric acids, natalizumab-associated herpes simplex encephalitis (n = 1 each)) was reduced by 59% (194.5±29 ng/ml, mean±SEM) in comparison to healthy controls (HC, 479.9±19.8 ng/ml, p<0.0001). iATP in 14 of these 16 patients was at or below 3(rd) percentile of healthy controls, similar to HIV-patients (n = 18). In contrast, CD4(+)-cell numbers were reduced in only 7 of 15 patients, for whom cell counts were available. iATP correlated with mitochondrial transmembrane potential (ΔΨ(m)) (iATP/ΔΨ(m)-correlation:tau = 0.49, p = 0.03). Whereas mean iATP of cross-sectionally analysed natalizumab-treated patients was unaltered (448.7±12 ng/ml, n = 150), iATP was moderately decreased (316.2±26.1 ng/ml, p = 0.04) in patients (n = 7) who had been treated already during the pivotal phase III trials and had received natalizumab for more than 6 years. 2/92 (2%) patients with less than 24 months natalizumab treatment revealed very low iATP at or below the 3(rd) percentile of HC, whereas 10/58 (17%) of the patients treated for more than 24 months had such low iATP-concentrations.

CONCLUSION

Our results suggest that bioenergetic parameters such as iATP may assist in risk stratification under mAb-immunotherapy of autoimmune disorders.

The molecular biology of human herpesvirus-6 latency and telomere integration

The genomes of herpesviruses establish latency as a circular episome. However, Human herpesvirus-6 (HHV-6) has been shown to specifically integrate into the telomeres of chromosomes during latency and vertically transmit through the germ-line. This review will focus on the telomere integration of HHV-6, the potential viral and cellular genes that mediate integration, and the clinical impact on the host.

Different characteristics of human herpesvirus 6 encephalitis between primary infection and viral reactivation

BACKGROUND

Pathogenesis of human herpesvirus 6 (HHV-6) encephalitis, in particular difference between HHV-6 encephalitis at the time of primary infection and reactivation remains unclear.

OBJECTIVES

To elucidate the mechanism of HHV-6 encephalitis at the time of primary infection and reactivation.

STUDY DESIGN

Twenty-two HHV-6 encephalitis patients at the time of primary infection, 6 febrile convulsion (FC) patients caused by HHV-6 infection, and 14 FC patients without HHV-6 infection (non HHV-6 FC) were enrolled. Additionally, 7 stem cell transplant recipients with HHV-6 encephalitis and eight adult controls were also enrolled in this study. Cerebrospinal fluid (CSF) HHV-6 DNA copy numbers and biomarkers levels were compared.

RESULTS

Low copy number of CSF HHV-6 DNA was detected in 7 of the 22 patients with HHV-6 encephalitis in primary infection, whereas all seven CSF samples collected from post-transplant HHV-6 encephalitis patients contained high viral DNA copy numbers (P<0.001). CSF concentrations of IL-6 (P=0.032), IL-8 (P=0.014), MMP-9 (P=0.004), and TIMP-1 (P=0.002) were significantly higher in patients with HHV-6 encephalitis in primary infection than non-HHV-6 FC. CSF IL-6 (P=0.008), IL-8 (P=0.015), and IL-10 (P=0.019) concentrations were significantly higher in patients with post-transplant HHV-6 encephalitis than adult controls.

CONCLUSION

The present study suggests that the characteristics of HHV-6 encephalitis are different between HHV-6 encephalitis at the time of primary infection and reactivation in transplant recipients.

A Swedish national post-marketing surveillance study of natalizumab treatment in multiple sclerosis

Background: A post marketing surveillance study was conducted to evaluate safety and efficacy of natalizumab in Swedish multiple sclerosis (MS) patients since its introduction in August 2006 until March 2010.

Methods: Patients were registered in the web-based Swedish MS-registry at 40 locations and evaluated every 6 months. Adverse events and clinical outcomes were recorded.

Results: One thousand one hundred and fifty-two patients were included (71.4% female) and 149 patients stopped treatment; the main reason was planned pregnancy. Anti-natalizumab antibodies were found in 4.5% (52 patients) of which 1.6% displayed persistent antibodies. Serious adverse events were rare, but included three cases with progressive multifocal leukoencephalopathy (PML). There were seven fatal cases, probably unrelated to the natalizumab treatment. For relapsing–remitting MS patients ( n = 901), mean Expanded Disability Status Scale (EDSS, −10.7%), Multiple Sclerosis Severity Scale (MSSS, −20.4%), Multiple Sclerosis Impact Scale (MSIS-29, physical −9.9%, psychological −13.3%) and Symbol Digit Modalities Test (SDMT, +10.7%) all showed significant improvements during 24 months of treatment with natalizumab. The Swedish web-based MS quality registry proved to function as a platform for post-marketing MS drug surveillance, providing long-term data regarding drug effects and adverse events beyond clinical trials.

Conclusions: Our results indicate that natalizumab is generally well tolerated and has sustained efficacy for patients with active MS, though the risk of PML is still an important concern.

Integrins as therapeutic targets: lessons and opportunities

The integrins are a large family of cell adhesion molecules that are essential for the regulation of cell growth and function. The identification of key roles for integrins in a diverse range of diseases, including cancer, infection, thrombosis and autoimmune disorders, has revealed their substantial potential as therapeutic targets. However, so far, pharmacological inhibitors for only three integrins have received marketing approval. This article discusses the structure and function of integrins, their roles in disease and the chequered history of the approved integrin antagonists. Recent advances in the understanding of integrin function, ligand interaction and signalling pathways suggest novel strategies for inhibiting integrin function that could help harness their full potential as therapeutic targets.

Natalizumab and progressive multifocal leukoencephalopathy: what are the causal factors and can it be avoided?

Natalizumab (Tysabri) was the first monoclonal antibody approved for the treatment of relapsing forms of multiple sclerosis (MS). After its initial approval, 3 patients undergoing natalizumab therapy in combination with other immunoregulatory and immunosuppressive agents were diagnosed with progressive multifocal leukoencephalopathy (PML). The agent was later reapproved and its use restricted to monotherapy in patients with relapsing forms of MS. Since reapproval in 2006, additional cases of PML were reported in patients with MS receiving natalizumab monotherapy. Thus, there is currently no convincing evidence that natalizumab-associated PML is restricted to combination therapy with other disease-modifying or immunosuppressive agents. In addition, recent data indicate that risk of PML might increase beyond 24 months of treatment.

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.

Reactivation of BK polyomavirus in patients with multiple sclerosis receiving natalizumab therapy

Natalizumab therapy in multiple sclerosis has been associated with JC polyomavirus-induced progressive multifocal leucoencephalopathy. We hypothesized that natalizumab may also lead to reactivation of BK, a related human polyomavirus capable of causing morbidity in immunosuppressed groups. Patients with relapsing remitting multiple sclerosis treated with natalizumab were prospectively monitored for reactivation of BK virus in blood and urine samples, and for evidence of associated renal dysfunction. In this cohort, JC and BK DNA in blood and urine; cytomegalovirus (CMV) DNA in blood and urine; CD4 and CD8 T-lymphocyte counts and ratios in peripheral blood; and renal function were monitored at regular intervals. BK subtyping and noncoding control region sequencing was performed on samples demonstrating reactivation. Prior to commencement of natalizumab therapy, 3 of 36 patients with multiple sclerosis (8.3%) had BK viruria and BK reactivation occurred in 12 of 54 patients (22.2%). BK viruria was transient in 7, continuous in 2 patients, and persistent viruria was associated with transient viremia. Concomitant JC and CMV viral loads were undetectable. CD4:CD8 ratios fluctuated, but absolute CD4 counts did not fall below normal limits. In four of seven patients with BK virus reactivation, transient reductions in CD4 counts were observed at onset of BK viruria: these resolved in three of four patients on resuppression of BK replication. No renal dysfunction was observed in the cohort. BK virus reactivation can occur during natalizumab therapy; however, the significance in the absence of renal dysfunction is unclear. We propose regular monitoring for BK reactivation or at least for evidence of renal dysfunction in patients receiving natalizumab.

Immune responses to JC virus in patients with multiple sclerosis treated with natalizumab: a cross-sectional and longitudinal study

BACKGROUND

Natalizumab is used to prevent relapses and progression of disability in patients with multiple sclerosis but has been associated with progressive multifocal leukoencephalopathy (PML). We aimed to better understand the associations between JC virus, which causes PML, and natalizumab treatment.

METHODS

We prospectively assessed patients with multiple sclerosis who started treatment with natalizumab. Blood and urine samples were tested for the presence of JC virus DNA with quantitative real-time PCR before treatment and at regular intervals after treatment onset for up to 18 months. At the same timepoints, by use of proliferation and enzyme-linked immunospot assays, the cellular immune responses against JC virus, Epstein-Barr virus, cytomegalovirus, myelin oligodendrocyte glycoprotein, and myelin oligodendrocyte basic protein (MOBP) were assessed. Humoral immune response specific to JC virus was assessed with an enzyme immunoassay. The same experiments were done on blood samples from patients with multiple sclerosis before and 10 months after the start of interferon beta treatment.

FINDINGS

We assessed 24 patients with multiple sclerosis who received natalizumab and 16 who received interferon beta. In patients treated with natalizumab, JC virus DNA was not detected in the blood at any timepoint. However, JC virus DNA was present in the urine of six patients and in most of these patients the concentrations of JC virus DNA were stable over time. Compared with pretreatment values, the cellular immune response was increased to cytomegalovirus at 6 months, to JC virus at 1, 9, and 12 months, and to Epstein-Barr virus and MOBP at 12 months. Humoral responses remained stable. There were no increases in cellular immune responses specific to the viruses or myelin proteins in the 16 patients treated with interferon beta.

INTERPRETATION

Natalizumab increases cellular immune responses specific to viruses and myelin proteins in the peripheral blood after 1 year, without evidence of viral reactivation.

FUNDING

Swiss National Foundation, Swiss Society for Multiple Sclerosis, and Biogen Dompé.

Chronic viral infections of the central nervous system: Aspects specific to multiple sclerosis

The involvement of a viral infection in the physiopathology of multiple sclerosis has been said to cause certain viruses to target the central nervous system and induce neuroinflammation leading to cell dysfunction, as seen, for example, by demyelination or neuronal death. The most recent results of the literature have focused on the Herpes family viruses (HHV-6 and HHV-4/Epstein-Barr virus) and their possible role in the development of multiple sclerosis. Even if no virus has been identified so far as the multiple sclerosis etiological agent, our aim here is to show that some viruses may be responsible for triggering or sustaining neurological diseases. This is particularly the case for Paramyxoviruses, in the late appearance of functional alterations, Picornaviruses, in inducing a breakdown of immune tolerance, epitope spreading and demyelination, and Herpes viruses in inducing T and B lymphocyte activation, T lymphocytes dysregulation and autoimmunity after their reactivation. Therefore, “common” viruses can play a role as potential modulators of the immune and nervous systems which, in the specific context of dysimmunity and genetic susceptibility, stimulate a favorable background to the development of multiple sclerosis. Tracing and studying viruses in multiple sclerosis patients may improve our understanding of their actual involvement in multiple sclerosis physiopathology.

Detection of human herpesvirus-6 variants in pediatric brain tumors: association of viral antigen in low grade gliomas

BACKGROUND

Human herpesvirus-6 (HHV-6) has been associated with a diverse spectrum of central nervous system (CNS) diseases and reported glial tropism.

OBJECTIVE

To determine if HHV-6 is present in a series of pediatric brain tumors.

STUDY DESIGN

Pediatric gliomas from 88 untreated patients represented in a tissue microarray (TMA) were screened for HHV-6 by nested polymerase chain reaction (PCR), in situ hybridization (ISH), and immunohistochemistry (IHC) and compared to non-glial tumors (N=22) and control brain (N=32). Results were correlated with tumor grade and overall survival.

RESULTS

HHV-6 U57 was detected by nested PCR in 68/120 (57%) tumors and 7/32 (22%) age-matched non-tumor brain (P=0.001). HHV-6 U31 was positive in 73/120 (61%) tumors and 11/32 (34%) controls (P=0.019). Seventy-two percent (43/60) of tumors were HHV-6 Variant A. HHV-6 U57 was confirmed by ISH in 83/150 (54%) tumors and 10/32 (31%) controls (P=0.021), revealing a non-lymphocytic origin of HHV-6. HHV-6A/B gp116/64/54 late antigen was detected by IHC in 50/124 (40%) tumors and 6/32 (18%) controls (P=0.013). Interestingly, 58% of low grade gliomas (N=67) were IHC positive compared to 19% of high grade gliomas (N=21, P=0.002) and 25% of non-gliomas (N=36, P=0.001). HHV-6A/B gp116/64/54 antigen co-localized with glial fibrillary acidic protein, confirming the astrocytic origin of antigen. Overall, there was no primary association between HHV-6A/B gp116/64/54 antigen detection and survival (P=0.861).

CONCLUSIONS

We provide the first reported series of HHV-6 detection in pediatric brain tumors. The predominance of HHV-6 in glial tumors warrants further investigation into potential neurooncologic disease mechanisms.

Detection of human herpesvirus-6 in adult central nervous system tumors: predominance of early and late viral antigens in glial tumors

The purpose is to determine the incidence of active and latent human herpesvirus-6 (HHV-6) infection in a large cohort of adult primary and recurrent CNS tumors. We screened a tissue microarray (TMA) containing more than 200 adult primary and recurrent CNS tumors with known clinical information for the presence of HHV-6 DNA by in situ hybridization (ISH) and protein by immunohistochemistry (IHC). One hundred six of 224 (47%) CNS tumors were positive for HHV-6 U57 Major Capsid Protein (MCP) gene by ISH compared to 0/25 non tumor control brain (P = 0.001). Fourteen of 30 (47%) tumors were HHV-6 MCP positive by nested PCR compared to 0/25 non-tumor brain controls (P = 0.001), revealing HHV-6 Variant A in 6 of 14 samples. HHV-6A/B early (p41) and late (gp116/64/54) antigens were detected by IHC in 66 of 277 (24%) (P = 0.003) and 84 of 282 (35%) (P = 0.002) tumors, respectively, suggesting active infection. HHV-6 p41 (P = 0.645) and gp116/64/54 (P = 0.198) antigen detection was independent of recurrent disease. Glial tumors were 3 times more positive by IHC compared to non glial tumors for both HHV-6 gp116/64/54 (P = 0.0002) and HHV-6 p41 (P = 0.004). Kaplan Meier survival analysis showed no effect of HHV-6 gp116/64/54 (P = 0.852) or HHV-6 p41 (P = 0.817) antigen detection on survival. HHV-6 early and late antigens are detected in adult primary and recurrent CNS tumors more frequently in glial tumors. We hypothesize that the glial-tropic features of HHV-6 may play an important modifying role in tumor biology that warrants further investigation.

Detection of human herpesvirus-6 in cerebrospinal fluid of patients with encephalitis

OBJECTIVE

Virus infections are the most common causes of encephalitis, a syndrome characterized by acute inflammation of the brain. More than 150 different viruses have been implicated in the pathogenesis of encephalitis; however, because of limitations with diagnostic testing, causative factors of more than half of the cases remain unknown.

METHODS

To investigate whether human herpesvirus-6 (HHV-6) is a causative agent of encephalitis, we examined for evidence of virus infection by determining the presence of viral sequence using polymerase chain reaction and assessed HHV-6 antibody reactivity in the cerebrospinal fluid of encephalitis patients with unknown cause. In a cohort study, we compared virus-specific antibody levels in cerebrospinal fluid samples of patients with encephalitis, relapsing-remitting multiple sclerosis, and other neurological diseases.

RESULTS

Our results demonstrated increased levels of HHV-6 IgG, as well as IgM levels, in a subset of encephalitis patients compared with other neurological diseases. Moreover, cell-free viral DNA that is indicative of active infection was detected in 40% (14/35) of encephalitis patients, whereas no amplifiable viral sequence was found in either relapsing-remitting MS or other neurological diseases patients. In addition, a significant correlation between polymerase chain reaction detection and anti-HHV-6 antibody response was also demonstrated.

INTERPRETATION

Collectively, these results suggested HHV-6 as a possible pathogen in a subset of encephalitis cases.

alpha4-Integrin antagonism with natalizumab: effects and adverse effects

Based on the results of two phase III clinical trials, the humanized recombinant monoclonal antibody natalizumab was approved for the treatment of relapsing forms of multiple sclerosis (MS). Since its initial approval in November 2004, it has been announced that six patients who received natalizumab in the context of clinical studies acquired an infection with the human polyoma virus JC and were diagnosed with progressive multifocal leukoencephalopathy (PML). Two of these individuals had a fatal outcome. Our groups recently showed that natalizumab therapy results in a reduction of CD4(+) T cells within the cerebrospinal fluid (CSF) that is ten-fold more pronounced than the reduction in the number of CD8(+) T lymphocytes. Interestingly, it appears that the effect of natalizumab on cell numbers in the CSF persists for at least 6 months after cessation of treatment. More recently, we studied the expression of major histocompatibility complex (MHC) I and II, and the number and phenotypes of leukocytes in cerebral perivascular spaces (CPVS). We observed that natalizumab therapy was associated with a significant decrease in the cell surface expression of MHC class II molecules, and the numbers of dendritic cells in CPVS. In addition, no CD4(+) T cells were detectable in this compartment. Our observations may explain the differential and prolonged effects of natalizumab therapy on different leukocyte subsets in the central nervous system. They also suggest that natalizumab treatment may result in prolonged immunosuppression in peripheral organs, and the delayed onset of adverse events.

Disease-modifying agents for multiple sclerosis: recent advances and future prospects

Multiple sclerosis (MS) is a chronic autoimmune disease of the CNS. Currently, six medications are approved for immunmodulatory and immunosuppressive treatment of the relapsing disease course and secondary-progressive MS. In the first part of this review, the pathogenesis of MS and its current treatment options are discussed. During the last decade, our understanding of autoimmunity and the pathogenesis of MS has advanced substantially. This has led to the development of a number of compounds, several of which are currently undergoing clinical testing in phase II and III studies. While current treatment options are only available for parenteral administration, several oral compounds are now in clinical trials, including the immunosuppressive agents cladribine and laquinimod. A novel mode of action has been described for fingolimod, another orally available agent, which inhibits egress of activated lymphocytes from draining lymph nodes. Dimethylfumarate exhibits immunomodulatory as well as immunosuppressive activity when given orally. All of these compounds have successfully shown efficacy, at least in regards to the surrogate marker contrast-enhancing lesions on magnetic resonance imaging. Another class of agents that is highlighted in this review are biological agents, namely monoclonal antibodies (mAb) and recombinant fusion proteins. The humanized mAb daclizumab inhibits T-lymphocyte activation via blockade of the interleukin-2 receptor. Alemtuzumab and rituximab deplete leukocytes and B cells, respectively; the fusion protein atacicept inhibits specific B-cell growth factors resulting in reductions in B-cells and plasma cells. These compounds are currently being tested in phase II and III studies in patients with relapsing MS. The concept of neuro-protection and -regeneration has not advanced to a level where specific compounds have entered clinical testing. However, several agents approved for conditions other than MS are highlighted. Finally, with the advent of these highly potent novel therapies, rare, but potentially serious adverse effects have been noted, namely infections and malignancies. These are critically reviewed and put into perspective.

[Choice of early and escalation treatment options for multiple sclerosis]

Recent advances in understanding of the immunopathogenesis of multiple sclerosis (MS) have led to the development of new treatment options. To date several immunomodulatory agents have been licensed for the treatment of relapsing-remitting MS. However, some debate remains on the optimal time point for initiating therapy. While there is general consensus on the benefit of an early treatment start, the issues of how to define "early MS" and how to identify patients with a "benign" disease course have not yet been finally addressed. Further open questions include the situations of treatment failure and therapeutic escalation. Here we summarize available data from studies on early treatment with immunomodulatory drugs for a first demyelinating event, also referred to as clinically isolated syndrome. Furthermore, options for the escalation of immunomodulatory therapy will be discussed, e.g. with the recently licensed monoclonal antibody natalizumab.