Human Herpes Virus-6 (HHV-6) Reactivation after Hematopoietic Cell Transplant and Chimeric Antigen Receptor (CAR)- T Cell Therapy: A Shifting Landscape

HHV-6B reactivation affects approximately half of all allogeneic hematopoietic cell transplant (HCT) recipients. HHV-6B is the most frequent infectious cause of encephalitis following HCT and is associated with pleiotropic manifestations in this setting, including graft-versus-host disease, myelosuppression, pneumonitis, and CMV reactivation, although the causal link is not always clear. When the virus inserts its genome in chromosomes of germ cells, the chromosomally integrated form (ciHHV6) is inherited by offspring. The condition of ciHHV6 is characterized by the persistent detection of HHV-6 DNA, often confounding diagnosis of reactivation and disease-this has also been associated with adverse outcomes. Recent changes in clinical practice in the field of cellular therapies, including a wider use of post-HCT cyclophosphamide, the advent of letermovir for CMV prophylaxis, and the rapid expansion of novel cellular therapies require contemporary epidemiological studies to determine the pathogenic role and spectrum of disease of HHV-6B in the current era. Research into the epidemiology and clinical significance of HHV-6B in chimeric antigen receptor T cell (CAR-T cell) therapy recipients is in its infancy. No controlled trials have determined the optimal treatment for HHV-6B. Treatment is reserved for end-organ disease, and the choice of antiviral agent is influenced by expected toxicities. Virus-specific T cells may provide a novel, less toxic therapeutic modality but is more logistically challenging. Preventive strategies are hindered by the high toxicity of current antivirals. Ongoing study is needed to keep up with the evolving epidemiology and impact of HHV-6 in diverse and expanding immunocompromised patient populations.

Cell Fusion and Syncytium Formation in Betaherpesvirus Infection

Cell–cell fusion is a fundamental and complex process that occurs during reproduction, organ and tissue growth, cancer metastasis, immune response, and infection. All enveloped viruses express one or more proteins that drive the fusion of the viral envelope with cellular membranes. The same proteins can mediate the fusion of the plasma membranes of adjacent cells, leading to the formation of multinucleated syncytia. While cell–cell fusion triggered by alpha- and gammaherpesviruses is well-studied, much less is known about the fusogenic potential of betaherpesviruses such as human cytomegalovirus (HCMV) and human herpesviruses 6 and 7 (HHV-6 and HHV-7). These are slow-growing viruses that are highly prevalent in the human population and associated with several diseases, particularly in individuals with an immature or impaired immune system such as fetuses and transplant recipients. While HHV-6 and HHV-7 are strictly lymphotropic, HCMV infects a very broad range of cell types including epithelial, endothelial, mesenchymal, and myeloid cells. Syncytia have been observed occasionally for all three betaherpesviruses, both during in vitro and in vivo infection. Since cell–cell fusion may allow efficient spread to neighboring cells without exposure to neutralizing antibodies and other host immune factors, viral-induced syncytia may be important for viral dissemination, long-term persistence, and pathogenicity. In this review, we provide an overview of the viral and cellular factors and mechanisms identified so far in the process of cell–cell fusion induced by betaherpesviruses and discuss the possible consequences for cellular dysfunction and pathogenesis.

In silico assessment of binding affinities of three dementia-protective Human Leukocyte Antigen (HLA) alleles to nine human herpes virus antigens

BACKGROUND

Human herpes viruses (HHV) have been implicated in dementia. Class II Human Leukocyte Antigens (HLA) play a critical role in host protection from foreign antigens including herpes viruses through stimulating antibody production against them. In the present study we investigated the in silico binding affinity of 9 H HV to three Class II HLA alleles that have been found to protect against dementia: DRB1*01:01, DRB1*13:02, and DRB1*15:01.

METHODS

A sliding window approach was used to partition the amino acid sequences of surface glycoproteins from HHV 1-8 into subsequences. The binding affinity of the HHV subsequences to Class II HLA surface receptor proteins was predicted using the Sturniolo method in the Immune Epitope Database and reported as a percentile rank. The binding affinity of HHV subsequences to protective alleles was compared to that of three dementia-neutral Class II HLA alleles: DRB1*03:01, DRB1*07:01, and DRB1*08:01.

FINDINGS

Binding affinity varied widely for each HLA allele, HHV type, and HHV subsequence. The protective alleles had significantly higher binding affinity that than the neutral alleles. The largest differences in binding affinity between the protective and neutral alleles was shown for HHV-6A and HHV-6B, which had the best overall binding affinity with the protective alleles.

INTERPRETATION

The dementia protection conferred by the three protective HLA alleles investigated here is related to their superior ability to bind and successfully eliminate HHV epitopes - in particular, HHV6 - that could otherwise cause dementia if they persisted.

Cross-sectional analysis of CD8 T cell immunity to human herpesvirus 6B

Human herpesvirus 6 (HHV-6) is prevalent in healthy persons, causes disease in immunosuppressed carriers, and may be involved in autoimmune disease. Cytotoxic CD8 T cells are probably important for effective control of infection. However, the HHV-6-specific CD8 T cell repertoire is largely uncharacterized. Therefore, we undertook a virus-wide analysis of CD8 T cell responses to HHV-6. We used a simple anchor motif-based algorithm (SAMBA) to identify 299 epitope candidates potentially presented by the HLA class I molecule B*08:01. Candidates were found in 77 of 98 unique HHV-6B proteins. From peptide-expanded T cell lines, we obtained CD8 T cell clones against 20 candidates. We tested whether T cell clones recognized HHV-6-infected cells. This was the case for 16 epitopes derived from 12 proteins from all phases of the viral replication cycle. Epitopes were enriched in certain amino acids flanking the peptide. Ex vivo analysis of eight healthy donors with HLA-peptide multimers showed that the strongest responses were directed against an epitope from IE-2, with a median frequency of 0.09% of CD8 T cells. Reconstitution of T cells specific for this and other HHV-6 epitopes was also observed after allogeneic hematopoietic stem cell transplantation. We conclude that HHV-6 induces CD8 T cell responses against multiple antigens of diverse functional classes. Most antigens against which CD8 T cells can be raised are presented by infected cells. Ex vivo multimer staining can directly identify HHV-6-specific T cells. These results will advance development of immune monitoring, adoptive T cell therapy, and vaccines.

This paper deals with the immune response to a very common virus, called human herpesvirus 6 (HHV-6). Most people catch HHV-6 in early childhood, which often leads to a disease known as three-day fever. Later in life, the virus stays in the body, and an active immune response is needed to prevent the virus from multiplying and causing damage. It is suspected that HHV-6 contributes to autoimmune diseases and chronic fatigue. Moreover, patients with severely weakened immune responses, for example after some forms of transplantation, clearly have difficulties controlling HHV-6, which puts them at risk of severe disease and shortens their survival. This can potentially be prevented by giving them HHV-6-specific "killer" CD8 T cells, which are cells of the immune system that destroy body cells harboring the virus. However, little is known so far about such T cells. Here, we describe 16 new structures that CD8 T cells can use to recognize and kill HHV-6-infected cells. We show that very different viral proteins can furnish such structures. We also observe that such T cells are regularly present in healthy people and in transplant patients who control the virus. Our results will help develop therapies of disease due to HHV-6.

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.

A Simple Proteomics-Based Approach to Identification of Immunodominant Antigens from a Complex Pathogen: Application to the CD4 T Cell Response against Human Herpesvirus 6B

Most of humanity is chronically infected with human herpesvirus 6 (HHV-6), with viral replication controlled at least in part by a poorly characterized CD4 T cell response. Identification of viral epitopes recognized by CD4 T cells is complicated by the large size of the herpesvirus genome and a low frequency of circulating T cells responding to the virus. Here, we present an alternative to classical epitope mapping approaches used to identify major targets of the T cell response to a complex pathogen like HHV-6B. In the approach presented here, extracellular virus preparations or virus-infected cells are fractionated by SDS-PAGE, and eluted fractions are used as source of antigens to study cytokine responses in direct ex vivo T cell activation studies. Fractions inducing significant cytokine responses are analyzed by mass spectrometry to identify viral proteins, and a subset of peptides from these proteins corresponding to predicted HLA-DR binders is tested for IFN-γ production in seropositive donors with diverse HLA haplotypes. Ten HHV-6B viral proteins were identified as immunodominant antigens. The epitope-specific response to HHV-6B virus was complex and variable between individuals. We identified 107 peptides, each recognized by at least one donor, with each donor having a distinctive footprint. Fourteen peptides showed responses in the majority of donors. Responses to these epitopes were validated using in vitro expanded cells and naturally expressed viral proteins. Predicted peptide binding affinities for the eight HLA-DRB1 alleles investigated here correlated only modestly with the observed CD4 T cell responses. Overall, the response to the virus was dominated by peptides from the major capsid protein U57 and major antigenic protein U11, but responses to other proteins including glycoprotein H (U48) and tegument proteins U54 and U14 also were observed. These results provide a means to follow and potentially modulate the CD4 T-cell immune response to HHV-6B.

Variants in Antiviral Genes are Risk Factors for Cognitive Decline and Dementia

A gene association study of factors regulating antiviral response such as interferon (IFN)-λ3, also known as IL-28B, mediator complex (Med) 23, and interferon regulatory factor (IRF) 7 with cognitive deterioration and Alzheimer's disease (AD) was performed. Differences in the TT genotype distribution of IL-28B single nucleotide polymorphism (SNP) between AD patients and controls were found. The GG genotype of Med23 gene appeared to influence the progression of the disease, being more frequent in the APOE ɛ4 negative elderly that developed AD during the five year follow-up. Leukocyte positivity for Epstein Barr virus (EBV) and human herpes virus (HHV)-6 DNA was analyzed. Med23 GG genotype correlated with the positivity to HHV-6 DNA. EBV and HHV-6 plasma IgG levels were also investigated and EBV IgG levels were increased in AD with the IRF7 GG genotype. A differential genetic background in genes regulating anti-virus responses was associated with an increased risk of cognitive decline and AD. EBV and HHV-6 appeared to be risk factors for AD in genetically susceptible elderly.

Evidence linking HHV-6 with multiple sclerosis: an update

Following reports of elevated antiviral antibodies in MS patient sera and viral DNA detection in MS plaques nearly two decades ago, the neurovirology community has actively explored how herpesviruses such as HHV-6 might be involved in MS disease pathogenesis. Though findings across the field are non-uniform, an emerging consensus of viral correlates with disease course and evidence of HHV-6-specific immune responses in the CNS provide compelling evidence for a role, direct or indirect, of this virus in MS. Ultimately, the only way to demonstrate the involvement, or lack thereof, of HHV-6 or other herpesviruses in this disease is through a controlled clinical trial of an efficacious antiviral drug.

Recent developments in animal models for human herpesvirus 6A and 6B

Progress in the identification of suitable animal models for human herpesvirus (HHV)-6A and HHV-6B infections has been slow. Recently, new models have been established, mainly for HHV-6A, which reproduce some pathological features seen in humans. Neuroinflammatory signs were observed in infected marmosets and CD46-transgenic mice; although viral replication was not prominent, persistence of viral DNA and specific immunologic responses were detected, suggesting an immune-mediated pathogenic mechanism. Pig-tailed macaques showed robust viral replication concomitant with acute-phase symptoms, and provided a model to study the effects of HHV-6A on AIDS progression. In humanized mice, viral replication was less evident, but infection led to T-cell alterations. Altogether, these recent developments have opened new perspectives for studying the pathogenic role of HHV-6A in humans.

Fifth and sixth diseases: more than a fever and a rash

While most parvovirus B19 or HHV-6 infections resolve without sequelae, rheumatologic and hemolytic complications and seizures can develop.

[Unresolved problems and the prospects for research in area of the multiple sclerosis: virologic, immunologic and therapeutic aspects]

Multiple sclerosis--important and unsolved problem of modern neurology. Despite a great deal of publications, in the modern theory of multiple sclerosis there remain many unresolved problems, without solving of which no further advances in the diagnosis and treatment can be possible. The present work elucidates blind spots in pathogenesis of the disease to indicate the most perspective directions of research, the results of which would allow the optimization of existing diagnostic and therapeutic algorithms. Microbial triggers, immunopathological mechanisms, association with immunodeficiencies, efficacy of the immunotherapy and side effects of the immunosuppressants as well as additional antimicrobial treatment are discussed.

Human Herpesvirus-6-Specific Interleukin 10-Producing CD4+T Cells Suppress the CD4+T-Cell Response in Infected Individuals

Human herpesvirus-6 (HHV-6) infection normally persists for the lifetime of the host and may reactivate with immunosuppression. The mechanism behind HHV-6 latent infection is still not fully understood. In this study, we observed that decreased proliferation of CD4+ T cells and PBMCs but not CD8+ T cells from HHV-6-infected individuals was stimulated with HHV-6-infected cell lysates. Moreover, HHV-6-stimulated CD4+ T cells from HHV-6-infected individuals have suppressive activity on naïve CD4+ T and CD8+ T cells from HHV-6-uninfected individuals. However, no increased proportion of CD4+ CD25+ Treg cells from HHV-6-infected individuals contributed to the suppressive activity of the HHV-6-stimulated CD4+ T cells from HHV-6-infected individuals. Transwell experiments, ELISA and anti-IL-10 antibody blocking experiment demonstrated that IL-10 may be the suppressive cytokine required for suppressive activity of CD4+ T cells from HHV-6-infected individuals. Results of intracellular interleukin (IL)-10 and IL-4 further implicated the HHV-6-specific IL-10-producing CD4+ T cells in the suppressive activity of CD4+ T cells from HHV-6-infected individuals. Results of intracellular interferon (IFN)-gamma demonstrated a decreased frequency of HHV-6-specific IFN-gamma-producing CD4+ T, but not CD8+ T cells in HHV-6-infected individuals, indicating that it was the CD4+ Th1 responses in HHV-6-infected individuals that were selectively impaired. Our findings indicated that HHV-6-specific IL-10-producing CD4+ T cells from HHV-6-infected individuals possess T regulatory type 1 cell activity: immunosuppression, high levels of IL-10 production, with a few cells expressing IFN-gamma, but none expressing IL-4. These cells may play an important role in latent HHV-6 infection.

Prevalence of HHV-6 and HHV-8 antibodies in patients with autism spectrum disorders

BACKGROUND/AIM

The etiology of autism spectrum disorders (ASD) still eludes investigators. Several viral infections have been associated with ASD etiopathogenesis but few studies have ever focused on the role of HHV-6 and HHV-8, two members of the herpesviridae family. The aim of the present study was to evaluate seropositivity rate and levels of antibodies to HHV6 and HHV-8 in children with ASD compared to controls.

PATIENTS AND METHODS

We measured and compared seropositivity rate and levels of antibodies to HHV-6 and HHV-8 in 30 children with ASD (14 with autistic disorder and 16 with non-autistic disorder ASD) and in 28 healthy controls of the same age.

RESULTS

Seropositivity rate and levels of the two antibodies were similar in cases and controls. Seropositivity rate and levels of antibodies were not correlated with disease severity in children with ASD.

CONCLUSION

Levels and seropositivity rate of antibodies to HHV-6 and HHV-8 do not differ between children with ASD and controls.

HHV-6 is ubiquitously found using Western blot in tonsils and adenoid tissues of healthy people

Few studies have examined the prevalence and cellular proclivity of latent human herpesvirus 6 (HHV-6) in healthy populations. Difficulties in detection of HHV-6 genome in different tissues using polymerase chain reaction (PCR) and immunohistochemistry (IHC) techniques have been reported by various researchers. We examined tonsils and adenoid tissues of 54 patients who had undergone tonsillectomy or adenoidectomy without any evidence of acute infection for the presence of latent HHV-6 infection. While we were investigating the prevalence of HHV-6, we tested the efficiency of PCR, IHC and Western Blot (WB) for detection of HHV-6 in tonsil tissues. We found that 100% of tonsil tissues were positive for HHV-6 with WB, 40% of tonsils were positive with PCR and no tonsil was positive with IHC. This result correlates well with most studies claiming HHV-6 is a ubiquitous organism in various populations and tissues. Western blot may be a good choice for detecting HHV-6 in tissues. Expression of the HHV-6 gp60/110 envelope protein disclosed by WB may indicate that HHV-6 does not have true latency. To our knowledge, this is the first report to use WB to test for HHV-6 in tissues.

Increased proportion of perforin-expressing CD8+T-cells indicates control of herpesvirus reactivation in children after stem cell transplantation

Hematopoietic stem cell transplantation (HSCT) is frequently complicated by viral reactivations. Early diagnosis of viral reactivations and preemptive therapy relies on frequent viralload monitoring. An easy marker of effective cytotoxicity in lymphopenia is lacking and therefore we studied perforin-expression in CD8+T-cells in children following HSCT. Prospectively, we weekly monitored viral loads and perforin-expression of CD8+T-cells in whole blood by FACS, until 4months after HSCT in children. 27 patients were included (median age 4,3, range 0.3-20,1years) of whom 19 developed viral reactivations. These patients showed higher percentages of perforin-expressing CD8+T-cells (17,2%, range 0-63%) than those without (6,8%; range 0-16%) (p=0.001). The increased percentage of perforin-expressing CD8+T-cells coincided with a decrease in viral load with a median interval between maximum viral load and maximum level of perforin-expression of 0,4weeks (range 0.1-7.1). We conclude that perforin-expression in CD8+T-cells may be a marker for effective antiviral T-cell reconstitution early after HSCT in children.

Virologic and immunologic evidence supporting an association between HHV-6 and Hashimoto's thyroiditis

Hashimoto's thyroiditis (HT) is the most common of all thyroid diseases and is characterized by abundant lymphocyte infiltrate and thyroid impairment, caused by various cell- and antibody-mediated immune processes. Viral infections have been suggested as possible environmental triggers, but conclusive data are not available. We analyzed the presence and transcriptional state of human herpesvirus 6 (HHV-6) in thyroid fine needle aspirates (FNA) and peripheral blood mononuclear cells (PBMCs) from 34 HT patients and 28 controls, showing that HHV-6 DNA prevalence (82% vs. 10%, p≤0.001) and viral load were significantly increased in FNA from HT patients, and thyrocytes from HT FNA displayed a 100-fold higher HHV-6 DNA load compared to infiltrating lymphocytes. In addition, while HHV-6 was strictly latent in positive samples from controls, a low grade acute infection was detected in HT samples. HHV-6 variant characterization was carried out in 10 HT FNA samples, determining that all specimens harbored HHV-6 Variant A.

The tropism of HHV-6 for thyroid cells was verified by infection of Nthy-ori3-1, a thyroid follicular epithelial cell line, showing that thyrocytes are permissive to HHV-6 replication, which induces de novo expression of HLA class II antigens. Furthermore, HHV-6-infected Nthy-ori3-1 cells become targets for NK-mediated killing, NK cells from HT patients show a significantly more efficient killing of HHV-6 infected thyroid cells than healthy controls, and HT patients have increased T-cell responses to HHV-6 U94 protein, associated to viral latency. These observations suggest a potential role for HHV-6 (possibly variant A) in the development or triggering of HT.

Hashimoto's thyroiditis (HT) is a very common autoimmune disease of the thyroid. In addition to genetic background, several viruses, including herpesviruses, have been suggested to play a role as possible environmental triggers of disease, but conclusive data are still lacking. The anecdotal presence of human herpesvirus 6 (HHV-6) in HT specimens prompted us to study a possible association between HHV-6 and HT. Our analysis of fine needle thyroid aspirates and blood from HT patients and controls shows that HHV-6 prevalence and load are highly increased in HT patients. Furthermore, HT-derived thyrocytes harbor active virus, whereas HHV-6 is strictly latent in the few virus-positive controls. We also report that HHV-6 infects thyroid cells, inducing de novo expression of HLA-II surface antigens. Consequently, thyrocytes might behave as antigen presenting cells. Interestingly, immune cells from HT patients kill HHV-6-infected thyrocytes more efficiently than controls. Also, HT patients, but not controls, have specific T-cell responses to HHV-6 U94 protein. It is difficult to prove etiologic links between viral infections and diseases, especially in the case of a ubiquitous agent such as HHV -6. Nevertheless, our findings indicate that HHV-6 might contribute to HT development, and argue for a pathogenic association between HHV-6 and HT.

HHV-6B induces IFN-lambda1 responses in cord plasmacytoid dendritic cells through TLR9

Human herpesvirus type 6B (HHV-6B) is a strong inducer of IFN-alpha and has the capacity to promote Th1 responses and block Th2 responses in vitro. In this study we addressed whether inactivated HHV-6B can also induce IFN lambda responses and to what extent interferons alpha and lambda affect Th1/Th2 polarization. We show that inactivated HHV-6B induced IFN-lambda1 (IL-29) but not IFN-lambda2 (IL-28A) responses in plasmacytoid DC and that this induction was mediated through TLR9. We have previously shown that HHV-6B promotes Th1 responses and blocks Th2 responses in both humans and mice. We now show that neutralization of IFN-alpha but not IFN-lambda1 blocked the HHV-6B-induced enhancement of Th1 responses in MLR, but did not affect the HHV-6-induced dampening of Th2 responses. Similarly, blockage of TLR9 counteracted HHV-6Bs effects on the Th1/Th2 balance. In addition, IFN-alpha but not IFN-lambda1 promoted IFN-gamma production and blocked IL-5 and IL-13 production in purified CD4+ T-cells. The lack of effect of IFN-lambda1 correlated with the absence of the IFN-lambda receptor IL-28Ralfa chain on the cell surface of both resting and activated CD4+ T-cells. We conclude that inactivated HHV-6B is a strong inducer of IFN-lambda1 in plasmacytoid DC and that this induction is TLR9-dependent. However, human CD4+ T-cells do not express the IFN-lambda receptor and are refractory to IFN-lambda1 treatment. The HHV-6B-induced alterations in the Th1/Th2 balance are instead mediated mainly through TLR9 and IFN-alpha.

Evaluation of viral antibodies in Iranian multiple sclerosis patients

OBJECTIVE

To evaluate the viral antibodies in new Iranian multiple sclerosis (MS) patients.

METHODS

In a cross-sectional study, sera from 61 MS patients and 60 healthy individuals were collected from January 2009 to March 2010 in the Immunology Department of Arak University of Medical Sciences, Arak, Iran, and examined for the presence of the anti-Epstein-Barr virus (EBV), human herpes virus 6 (HHV-6), measles, mumps, and para-influenza viruses IgG and IgM using an enzyme-linked immunosorbent assay or immunofluorescence.

RESULTS

There were significant differences between the MS patients and the healthy individuals (controls) in the seroprevalence of anti-HHV-6 IgM (odds ratio [OR]=4.3, 95% confidence interval [CI]=2-9.3, p=0.001); anti-HHV-6 IgG (OR=2, 95% CI=1-4, p=0.04); anti-measles IgM (OR=3.2, 95% CI=1.5-6.9, p=0.002); and the anti-mumps IgM (OR=4.1, 95% CI=1.9-8.8, p=0.0001) and IgG (OR=9.5, 95% CI=3-29.6, p=0.0001). Almost all MS patients and the control individuals were negative to EBV and parainfluenza IgM.

CONCLUSION

These results confirm an association between the incidence of MS and the antibodies to HHV-6 and the measles and mumps viruses, and show induction of a primary immune response (IgM), or virus reactivation, in MS patients. These viruses may have an important role in development of MS as an initial trigger in this geographical area.

Etiology of measles suspect cases reported in 2006-2007 in Poland

To achieve measles elimination, an efficient surveillance system for rash illnesses is necessary. The aim of the present study was to ascertain which viruses, other than measles, are causing measles-like illnesses (MLIs) in Poland. Serum samples (n=278) collected from MLI cases and submitted to the National Reference Laboratory during 2006-2007 were investigated for anti-measles (MeV), rubella (RUBV), parvovirus B19 (B19V), Epstein-Barr (EBV) and herpesvirus type-6 (HHV-6) IgM presence. Age was strongly associated with MLIs etiology. In the youngest age group, 0-4 years, MeV and HHV-6 infection were prevailing, while in group of 5-9 years--RUBV and B 19V. Measles was confirmed more often in patients with high fever (p < 0.001) and with rash lasting longer than 5 days (p < 0.001). The type of rash was not significantly associated with MeV infection. Our results strongly suggest that according to WHO EURO strategic plan, Poland is close to elimination phase. High number of MLIs were caused by pathogens other than measles. Addition of anti-B 19V IgM testing to routine MLIs screening protocol may improve system performance in the more advanced stages of measles elimination.

Human herpesvirus 6 infection as a trigger of multiple sclerosis

We systematically reviewed the existing evidence to determine whether a relationship exists between infection with human herpesvirus 6 (HHV-6) and multiple sclerosis (MS) and, if so, to define the strength of that relationship. The following terms were used in searches of the Entrez-PubMed database (1966-2009): human herpes virus 6, HHV 6, demyelination, multiple sclerosis, pathogenesis, diagnosis, serology, cerebrospinal fluid, IgG antibodies, IgM antibodies, PCR, and lymphoproliferative techniques. Study quality was assessed using the criteria proposed by Moore and Wolfson and by the classification criteria used by the Canadian Task Force on the Periodic Health Examination. Studies were categorized both by experimental technique and by quality (high [A], intermediate [B], and low [C]) as determined by the Moore and Wolfson criteria. Overall, 25 (41%) of 61 studies, 15 (60%) of which were classified as A quality, reached a statistically significant result. According to the Canadian Task Force classification, all studies were categorized as evidence of quality II-1. Limitations of the available experimental techniques and perspectives for future research are discussed. The current review supports the need for further, objective, evidence-based examination of the relationship between HHV-6 infection and multiple sclerosis.

Human herpesvirus 6B induces phenotypic maturation without IL-10 and IL-12p70 production in dendritic cells

Human herpesvirus 6B (HHV-6B) is the causative agent of the common childhood febrile illness, exanthema subitum. The virus is predominantly regarded as a T-cell tropic virus, although in reality it has the ability to infect a wide variety of cell types including monocytes, macrophages and dendritic cells (DC). Although DC are important immune regulators, the modulating effects of HHV-6B on DC are controversial. Here, we examine the phenotypic and functional consequences of HHV-6B infection of DC. The addition of HHV-6B to immature DC led to expression of the nuclear viral p41 protein and cell surface expression of the viral glycoprotein gp60/110 consistent with HHV-6B infection. Nevertheless, HHV-6B did not induce noticeable cytopathogenic effects or cell death in infected DC. Importantly, HHV-6B infection induced a partial phenotypic maturation of immature DC as demonstrated by a substantial increase in the expression of HLA-DR, CD86 and CD40, whereas only a minor increase in CD80 and CD83 was observed. This phenotypic maturation was, however, not followed by functional maturation, because HHV-6B infection did not induce IL-10 and IL-12p70 production in immature DC. However, infected DC were still able to react to bacteria-derived stimuli such as lipopolysaccaharide by an even more pronounced production of IL-10 and IL-12p70 when compared to that of uninfected DC.

Association between human herpesvirus 6 and occurrence of multiple sclerosis among Jordanian patients

OBJECTIVES

Multiple sclerosis (MS) is hypothesized to be caused by an infectious agent that initiates an autoimmune reaction. Among the infectious agents linked to MS is human herpesvirus 6 (HHV-6). Due to the high occurrence of MS among Jordanian population and the deficiency of MS studies in Jordan, the prevalence of HHV-6 in sera and cerebrospinal fluids (CSFs) of 36 MS patients was investigated.

MATERIALS AND METHODS

To increase the sensitivity of detection, nested polymerase chain reaction was utilized.

RESULTS

Although we were able to detect HHV-6 DNA in serum samples of 26% MS patients, no significant difference was found when compared to control individuals. In addition, lack of association between MS and presence of viral DNA in CSF samples was observed. Even within the analyzed MS patient population, an association of HHV-6 and MS in terms of gender, type of diagnosis, symptoms and disease score was not identified among Jordanian patients.

CONCLUSIONS

Although these results indicate lack of apparent association between HHV-6 to MS among Jordanian patients, heterogeneity related to genetic polymorphism as well as geographical distribution of the disease and of pathogens may be of significance.

[Drug-induced hypersensitivity syndrome and HHV-6 reactivation]

Drug-induced hypersensitivity syndrome (DIHS) is an adverse reaction with clinical signs of fever, rash, and internal organ involvement. The culprit drugs of DIHS are limited to several drugs such as carbamazepine, phenytoin, phenobarbital, zonisamide, allopurinol, salazosulfapyridine, diaphenylsulphone, and mexiletine. The association of HHV-6 reactivation with DIHS has been known. Flaring of symptoms such as fever and hepatitis is closely related to HHV-6 reactivation. A combination of immunologic reaction to a drug and HHV-6 reactivation results in the severe course of DIHS.

Role of dendritic cells infected with human herpesvirus 6 in virus transmission to CD4(+) T cells

Human herpesvirus 6 (HHV-6) is a ubiquitous betaherpesvirus that predominantly infects and replicates in CD4(+) T lymphocytes. However, the mechanism of HHV-6 transmission to T cells from the peripheral mucosa is unknown. Here we found that dendritic cells (DCs) can transmit HHV-6 to T cells, resulting in productive infection. In immature monocyte-derived DCs (MDDCs) infected with HHV-6, viral early and late antigens were expressed, and nucleocapsids containing a DNA core were observed, although few virions were detected in the cytoplasm by electron microscopy, indicating that the maturation of HHV-6 virions may be incomplete in MDDCs. However, HHV-6 transmission from MDDCs to stimulated CD4(+) T cells occurred efficiently in coculture of these cells, but not from MDDCs culture supernatants. This transmission was partially inhibited by treating the DCs with a viral DNA synthesis blocker, indicating that viral replication in MDDCs is required for this transmission. Furthermore, myeloid DCs and plasmacytoid DCs infected with HHV-6 could also transmit the virus to stimulated T cells. Thus, DCs may be the first cell population targeted by HHV-6 and could play an important role in the virus' transmission to T cells for their further propagation.

[Hypogammaglobulinemia with a clinical course similar to that of drug-induced hypersensitivity syndrome]

A 30-year-old man consulted a local hospital because of upper abdominal pain and tarry stool and was admitted because of duodenal ulcer and hepatic dysfunction. On the fifth hospital day, he developed fever and erythema on the upper body. Liver biopsy demonstrated giant cell hepatitis, and interferon alpha was therefore administered. Liver function improved, though total bilirubin increased to 22.3 mg/dl. The eruption and fever improved in the 3rd hospital week, deteriorated again in the 5th hospital week, and then improved again in the 8th hospital week. Thereafter, he was transferred to our hospital for detailed examination of atypical lymphocytosis, lymphopenia, and hypogammaglobulinemia. Many lymph nodes measuring about 1 cm were detected by palpation. After admission to our hospital, lymphoadenopathy and fever improved. We measured the level of HHV-6 antibody since the clinical course was similar to that of drug-induced hypersensitivity syndrome (DIHS). HHV-6 IgG was x2,560, although it had been x160 at the previous hospital. The clinical course appeared similar to that of DIHS, but drugs known to cause DIHS had not been administered.

Relation between psychoneuroendocrine profile in stressful conditions and antibodies to herpesvirus 6 and 7

The aim of the present study is to evaluate whether the individual susceptibility to infectious disease is influenced by the psychological profile of cadets exposed to stressful events associated with military lifestyle in academy and if the neuroendocrine responses to stressful events is related with humoral immunity estimated by measuring antibody titres to human herpesvirus (HHV-6)7 (HHV-7) and to what extent it is influenced by personality traits. It has been observed that cadets with lower psychoaptitude scores (1-2) have a significant higher susceptibility to infectious disease (x2=7.95; p=0.019) compared to subjects with higher scores. A positive relationship between cortisol and antibody titers to HHV-6 (r=0.304; p=0.024) it has been found. It can be interesting to observe that antibody titers on HHV-6 are also related to psychoaptitude profile (r=0.239; p=0.044). The antibody titers to HHV-7 are negatively related to the 5 scales of BFQ and in particular with subdimension Co (cordiality) of BFQ (r=0.401; p=0.002). The survey carried out on over 1,500 cadets of the Military Academy of Modena shows that the susceptibility to infectious diseases during the first six months of admission to the Academy seem to be influenced by the psychoaptitudinal profile. The finding of a positive relationship between serum cortisol and antibody vs HHV-6 suggests that the impairment of the immune system linked to circulatory cortisol levels may induce a reactivation of a latent herpesvirus 6 with related increase of antibody titers.

The accuracy of anti-human herpesvirus 6 IgM detection in children with recent primary infection

Human herpesvirus 6 (HHV-6) has been shown to infect almost all children by 4 years of age. Even with a typical clinical presentation, HHV-6 infection is misdiagnosed frequently as measles or rubella. The aim of this study was to assess the accuracy of the IgM test for detection of recent primary HHV-6 infection. The study was conducted between January, 1998 and December, 2006 at primary health care units in Niterói, Rio de Janeiro, Brazil. Sera from 185 children, in whom measles, rubella, dengue fever and parvovirus B19 infections were excluded, were studied for anti-HHV-6 IgG and IgM antibodies using an indirect immunofluorescence test. Seventy-one (38.4%) of the children had evidence of primary HHV-6 infection. Taking the IgG avidity test as the "gold standard", the following results for IgM were obtained-sensitivity: 76.1%; specificity: 87.5%; accuracy: 82.4%. This study confirmed the low accuracy of IgM detection for the diagnosis of primary HHV-6 infection.

HHV-6A in syncytial giant-cell hepatitis

Syncytial giant-cell hepatitis is a rare but severe form of hepatitis that is associated with autoimmune diseases, drug reactions, and viral infections. We used serologic, molecular, and immunohistochemical methods to search for an infectious cause in a case of syncytial giant-cell hepatitis that developed in a liver-transplant recipient who had latent infection with variant B of human herpesvirus 6 (HHV-6B) and who had received the organ from a donor with variant A latent infection (HHV-6A). At the onset of the disease, the detection of HHV-6A (but not HHV-6B) DNA in plasma, in affected liver tissue, and in single micromanipulated syncytial giant cells with the use of two different polymerase-chain-reaction (PCR) assays indicated the presence of active HHV-6A infection in the patient. Expression of the HHV-6A-specific early protein, p41/38, but not of the HHV-6B-specific late protein, p101, was demonstrated only in liver syncytial giant cells in the absence of other infectious pathogens. The same markers of HHV-6A active infection were documented in serial follow-up samples from the patient and disappeared only at the resolution of syncytial giant-cell hepatitis. Neither HHV-6B DNA nor late protein was identified in the same follow-up samples from the patient. Thus, HHV-6A may be a cause of syncytial giant-cell hepatitis.

The associations between psychosocial stress and the frequency of illness, and innate and adaptive immune function in children

OBJECTIVE

Family processes have a substantial impact on children's social and emotional well-being, but little is known about the effects of family stress on children's physical health. To begin to identify potential links between family stress and health in children, we examined associations between specific aspects of family psychosocial stress and the frequency of illnesses in children, measures of innate and adaptive immune function, and human herpesvirus 6 (HHV-6) reactivation.

STUDY DESIGN

Prospective study of 169 ambulatory school-age children and parents. Parents completed multiple assessments of stress at 7 sequential six-month visits and maintained weekly illness diaries for their children over three years using a thermometer to record fever. Children had blood obtained for HHV-6 and immune function studies at each visit including natural killer (NK) cell function and the percentage of CD4 and CD8 cells associated with immune control of cytomegalovirus (CMV).

RESULTS

Parental psychiatric symptoms were associated with a higher frequency of illnesses: for each 1 U increase in symptom score children had an increased 1-year rate of total illnesses of 40% (rate ratio, 1.40; 95% CI, 1.06-1.85) and febrile illnesses of 77% (rate ratio, 1.77, 95% CI, 1.00-3.13). Parental psychiatric symptom scores were also associated with enhanced NK cell function (estimate, 0.15; 95% CI, 0.05-0.26) and increased percentages of CD8+CD28-CD57+ cells in the blood of CMV seropositive children (estimate, 2.57; 95% CI, 0.36-4.79). HHV-6 reactivation was not detected.

CONCLUSIONS

There is an association between specific psychosocial stress exposure and rates of illness and immune function in normally developing children.

Drug-induced hypersensitivity syndrome with rapid hematopoietic reconstitution during treatment for acute myeloid leukemia

Drug-induced hypersensitivity syndrome (DIHS) is a rare but severe life-threatening, drug-induced, systemic hypersensitivity reaction. We report two patients who developed DIHS during treatment for acute myeloid leukemia. Awareness of DIHS is necessary when systemic eruptions and high fever occur in leukemic patients, especially with rapid hematopoietic recovery after chemotherapies.

IgM and avidity of IgG antibodies in primary HHV-6 infections

Primary HHV-6 infection could be diagnosed by enzyme immunoassay from a single serum using IgG avidity test based on results obtained from 43 patients, 26 with seroconversion and 17 with variable antibody levels. The avidity was less than 30% in all patients with seroconversion. HHV-6 IgM appeared non-specific.

Evidence for human herpesvirus 6 variant A antibodies in multiple sclerosis: diagnostic and therapeutic implications

Human herpesvirus 6 (HHV-6) has been linked to the pathogenesis of multiple sclerosis (MS). HHV-6 antibodies in serum and cerebrospinal fluid (CSF) of 27 patients with clinically definite MS (CDMS) were compared with age- and sex-matched controls, including various other neurological diseases and symptoms (OND). In addition, we studied a series of 19 patients with clinically or laboratory supported possible MS (CPMS). Seroprevalence to HHV-6A was 100% in patients with MS, both in CDMS and CPMS, compared to 69.2% in patients with OND (P = .001 and .007). The mean immunoglobulin G (IgG) titers were significantly higher in patients with CDMS and CPMS than in controls (P = .005 and .00002). The proportion of acute primary infections without CSF involvement was similar in all groups; however, primary infections with intrathecal HHV-6 antibody production were more frequent in MS. In CSF, HHV-6A-specific antibodies were present in three (11.5%) and four (21.1%) patients with CDMS and CPMS, compared to none with OND (P = .06 and .01, respectively). Serological suggestions to HHV-6A infection occurred more often in both CDMS and CPMS than in OND (14.8% versus 21.1% versus 3.8%). We conclude that a subpopulation of MS patients, and even a greater proportion of possible MS subjects, has serological evidence of HHV-6A infection, which might provide new markers for diagnosis and therapy.

[Research Value of Multi-clone Cell Line: A Comment for the 30th Anniversary of J6-1 Human Leukemic Cell Line]

J6-1 cell line is the first leukemic cell line established in China. It is a multi-clone cell line infected with both EBV and HHV-6. Many cytokines, receptors and other genes were cloned from J6-1 cell line since its establishment 30 years ago. Valuable information on leukemic characteristics and functions were obtained from the studies on this cell line, which could be categorized into several research subjects. These achievements implied the unique research value of multi-clone cell lines. This comment focuses attention on research advance of the J6-1 leukemic cell line in 30 years, including heterogeneity and multi-cloning of J6-1 cells, survival mechanism of J6-1 cell populations, abnormal intercellalar communication of J6-1 cells with its significance and inspiration from J6-1 cell line.

Human herpes virus 6 and multiple sclerosis: a Finnish twin study

OBJECTIVE

To investigate the possible association of human herpes virus 6- (HHV6) infection and multiple sclerosis (MS).

BACKGROUND

Despite intensive investigations of genetic and environmental factors, the etiopathogenesis of MS remains unknown. HHV6 is a possible candidate in that it is neurotropic, able to induce demyelination and become latent and be reactivated. We had access to The Finnish National Twin Cohort, which provided a unique opportunity to study the association between HHV6 and MS in genetically homogenous patients.

METHODS

Thirty-four serum samples from 17 MS twin pairs and 12 cerebrospinal fluid (CSF) samples from six MS twin pairs were tested by PCR specific for HHV6. Immunoglobulin (Ig) G and M response against HHV6 in serum and CSF were analysed using ELISA method. The samples were collected during a remission of the disease.

RESULTS

No HHV6 DNA was found in any serum (n=34) or CSF (n=12) samples. Eighty-eight percent of the twins with MS and 86% of the healthy twin siblings were positive for IgG in serum. One twin with MS was also positive for IgM in serum, whereas none of the healthy twins was IgM positive. All CSF samples were negative for IgG and IgM in both groups.

CONCLUSIONS

During a clinical remission of MS the detection of antibodies against HHV6 in CSF and HHV6 DNA in serum, CSF supernatant or CSF leukocytes is unlikely. However, the results do not exclude a possibility of HHV6 reactivation during MS exacerbation or acute HHV6 infection being one of the triggering agents in development of MS long before its clinical manifestation.

Association of human herpesvirus 6 reactivation with the flaring and severity of drug-induced hypersensitivity syndrome

BACKGROUND

Drug-induced hypersensitivity syndrome (DIHS) is an adverse reaction with clinical signs of fever, rash and internal organ involvement. In the vast majority of patients in Japan, the causative drugs for DIHS are limited to the following eight: carbamazepine, phenytoin, phenobarbital, zonisamide, mexiletine, dapsone, salazosulfapyridine and allopurinol. The association of human herpesvirus (HHV)-6 reactivation with DIHS has been reported by various groups.

OBJECTIVES

To confirm the relationship between the flaring and severity of DIHS and HHV-6 reactivation.

METHODS

We evaluated 100 patients with drug rash and systemic symptom(s) caused by the drugs associated with DIHS. HHV-6 reactivation was examined by serological antibody assay and quantitative real-time polymerase chain reaction assay of serial serum samples.

RESULTS

Anti-HHV-6 IgG titres increased in 62 of 100 patients, 14-28 days after the onset of symptoms. These patients suffered from severe organ involvement and a prolonged course compared with 38 patients showing no reactivation of HHV-6. Significant amounts of HHV-6 DNA were detected in serum samples from 18 of the 62 patients. Flaring of symptoms such as fever and hepatitis was closely related to HHV-6 reactivation in these 18 patients. It should be emphasized that all five patients with fatal outcome and 10 patients with renal failure were in the HHV-6 reactivation group.

CONCLUSIONS

A combination of immunological reaction to a drug and HHV-6 reactivation results in the severe course of DIHS. The demonstration of HHV-6 reactivation is a useful marker of diagnosis as well as prognosis in DIHS.

HHV-6 and the immune system: mechanisms of immunomodulation and viral escape

Clinical and experimental evidence indicates that human herpesvirus 6 (HHV-6) can interfere with the function of the host immune system through a variety of mechanisms. Both HHV-6A and B can infect, either productively or nonproductively, several types of immune cells. The primary target for HHV-6 replication, both in vitro and in vivo, is the CD4+ T lymphocyte, a pivotal cell in the generation of humoral and cell-mediated adaptive immune responses. HHV-6A, but not B, also replicates in various cytotoxic effector cells, such as CD8+ T cells, gammadelta T cells and natural killer cells. In professional antigen-presenting cells like macrophages and dendritic cells, HHV-6 infection is typically nonproductive; yet, it induces dramatic functional abnormalities, including a selective suppression of IL-12, a critical cytokine in the generation of Th1-polarized antiviral immune responses. This and other immunomodulatory effects seem to be mediated by the engagement of the primary HHV-6 receptor, CD46. Moreover, HHV-6 infection results in a generalized loss of CD46 expression in lymphoid tissue, which may lead to an aberrant activation of autologous complement. Additional mechanisms of immunomodulation by HHV-6 include alterations in cell surface receptor expression and cytokine/chemokine production. HHV-6 can also modulate influence responses through the expression of virally-encoded homologs of chemokines and chemokine receptors. By modulating specific antiviral immune responses, HHV-6 can facilitate its own spread and persistence in vivo, as well as enhance the pathogenic effects of other agents, such as human immunodeficiency virus.

Activation of human herpesviruses 6 and 7 in patients with chronic fatigue syndrome

BACKGROUND

Human herpesvirus 6 (HHV-6) and 7 (HHV-7) have been suggested as possible triggering agents for chronic fatigue syndrome (CFS).

OBJECTIVES

To determine the possible association of HHV-6 and HHV-7 infections with CFS.

STUDY DESIGN

The prevalence of latent/persistent and active viral infections by nPCR, characteristic of HHV-6 variants using restriction endonuclease analysis and changes of lymphocyte subsets in peripheral blood by laser flow-cytometry in 17 CFS patients was examined. In addition, 12 patients with unexplained chronic fatigue and 20 blood donors (BD) were studied.

RESULTS

No difference in prevalence of latent/persistent single viral infections between the patients and BD was found but dual infection rate was significantly higher in CFS patients. Active HHV-6 and dual (HHV-6 + HHV-7) infections were detected in CFS patients only and frequency of HHV-7 reactivation was also significantly higher in these patients. HHV-6 variant B was predominant in CFS patients (12/13). The changes of immunological parameters in CFS patients with active dual infection were characterized by significant decrease of CD3+ and CD4+ T cells, significant increase of CD95+ cells and decrease of CD4+/CD8+ ratio.

CONCLUSIONS

HHV-6 and HHV-7 may be involved in the pathogenesis of CFS and reactivation of both viruses may provoke changes in the phenotype of circulating lymphocytes.

Post-transplant acute limbic encephalitis: clinical features and relationship to HHV6

BACKGROUND

Acute limbic encephalitis has been reported in the setting of treatment-related immunosuppression and attributed to human herpesvirus-6 (HHV6) infection. Clinical and laboratory features of the syndrome, however, have not been well characterized.

METHODS

We describe the clinical, EEG, MRI, and laboratory features of nine patients with acute limbic encephalitis after allogeneic hematopoietic stem cell transplantation (HSCT). To explore the relationship between HHV6 and this syndrome, we reviewed available CSF HHV6 PCR results from all HSCT patients seen at our center from March 17, 2003, through March 31, 2005.

RESULTS

Patients displayed a consistent and distinctive clinical syndrome featuring anterograde amnesia, the syndrome of inappropriate antidiuretic hormone secretion, mild CSF pleocytosis, and temporal EEG abnormalities, often reflecting clinical or subclinical seizures. MRI showed hyperintensities within the uncus, amygdala, entorhinal area, and hippocampus on T2, fluid-attenuated inversion recovery (FLAIR), and diffusion-weighted imaging (DWI) sequences. CSF PCR assays for HHV6 were positive in six of nine patients on initial lumbar puncture. All patients were treated with foscarnet or ganciclovir. Cognitive recovery varied among long-term survivors. The one brain autopsy showed limbic gliosis and profound neuronal loss in amygdala and hippocampus. Among 27 HSCT patients with CSF tested for HHV6 over a 2-year period, positive results occurred only in patients with clinical limbic encephalitis.

CONCLUSIONS

Patients undergoing allogeneic hematopoietic stem cell transplantation are at risk for post-transplant acute limbic encephalitis (PALE), a distinct neurologic syndrome. Treatment considerations should include aggressive seizure control and, possibly, antiviral therapy. PALE can be associated with the CSF presence of human herpesvirus-6, but the pathogenic role of the virus requires further exploration.

Transmission of integrated human herpesvirus-6 in allogeneic hematopoietic stem cell transplantation

Human herpesvirus 6 (HHV-6) viremia, as detected by polymerase chain amplification, occurs in approximately half of allogeneic hematopoietic stem cell transplant recipients. The significance of such viremia is incompletely understood, but HHV-6 encephalitis and bone marrow suppression are increasingly being recognized in patients with high viral DNA. We report two patients in whom donor-to-recipient transmission occurred through hematopoietic transplant by means of chromosomally integrated (CI) HHV-6. Iatrogenic transmission manifested at engraftment as asymptomatic elevation of HHV-6 viral DNA of 3600 and 15 400 DNA copies/ml in plasma and 6.1 x 10(6) and 9.7 x 10(5) DNA copies/ml in the whole blood. Both donors had elevated plasma HHV-6 PCR at 5.6 x 10(4) and 1.3 x 10(5) DNA copies/ml and strikingly elevated whole blood HHV-6 levels at 4.1 x 10(6) and 4.7 x 10(6) DNA copies/ml, respectively. CI of the virus was traced to the mother of one patient and his donor. CI of HHV-6 may confound the interpretation of HHV-6 viremia after stem cell transplantation; consideration of the possibility of CI HHV-6 will avoid unnecessary antiviral therapy.

Activation of endogenous retrovirus reverse transcriptase in multiple sclerosis patient lymphocytes by inactivated HSV-1, HHV-6 and VZV

Human endogenous retroviruses (HERVs) and herpesviruses have been associated with the development of multiple sclerosis (MS). These virus groups interact with each other and have been shown to induce synergistic immune responses. Here, we focus on the possible role of herpesviruses as contributing factors in HERV activation. We demonstrate the ability of HSV-1, HHV-6, and VZV antigens to induce higher RT activity in peripheral lymphocytes from MS patients vs. controls during the first 6 days post-antigen stimulation. On subsequent days, only VZV can sustain the increase in the RT expression in cells from MS patients. The RT induction does not depend on herpes replication.

[The rate of human herpes virus type 6 and cytomegalovirus among HIV-infected and healthy women from Chelyabinsk and Moscow]

Human herpes virus type 6 (H HV-6) and cytomegalovirus (CMV) seroprevalence among HIV-infected and healthy women of childbearing age from Chelyabinsk and Moscow was measured with ELI - SA test-system for detection of antibodies to respective viruses. Seropositivity to HHV-6 was detected in 93.5% of HIV-infected women, that is 1.2 times more often than in healthy woman of child-bearing age. Seropositivity to CMV was detected in 87% of HIV-infected women, that is 1.05 times more often than in healthy woman of childbearing age. Low titers to HHV-6 and CMV were detected in seropositive healthywomen more frequently (in 44.1 and 48.4% respectively) whereas intermediate and high titers prevailed in HIV-infected women (in 73.9% for HHV-6 and 31.4% for CMV).

Risk factors for developing human herpesvirus 6 (HHV-6) reactivation after allogeneic hematopoietic stem cell transplantation and its association with central nervous system disorders

We prospectively evaluated the incidence of human herpesvirus 6 (HHV-6) DNAemia after allogeneic hematopoietic stem cell transplantation (HSCT) using quantitative plasma real-time polymerase chain reaction. Of 46 recipients of bone marrow or peripheral blood stem cell transplantation (BMT/PBSCT) from related (n = 11) or unrelated donors (n = 22), and cord blood transplantation (CBT) from unrelated donors (n = 13), 22 (47.8%) developed HHV-6 DNAemia. HHV-6 DNA levels ranged from 200 to 200,000 copies/mL of plasma, and HHV-6 DNAemia was observed significantly more frequently after CBT than after BMT/PBSCT (92.3% vs 30.3%; P < .001). Multivariate analyses identified CBT (vs BMT/PBSCT), HLA mismatches between recipient and donor, and low anti-HHV-6 IgG titer before transplantation as the only risk factors for developing HHV-6 DNAemia. Three patients developed central nervous system (CNS) disorders with detectable HHV-6 DNA in the cerebrospinal fluid; all of these patients simultaneously developed HHV-6 DNAemia. These results suggest that HHV-6 DNAemia is frequently observed after allogeneic HSCT, especially in patients with the aforementioned risk factors. Thus, together with the assessment of risk factors, monitoring of HHV-6 DNAemia could be a useful asset in diagnosing HHV-6-associated CNS disorders.

Epitope mapping of a monoclonal antibody specific for human herpesvirus 6 variant A immediate-early 2 protein

BACKGROUND

Human herpesvirus 6 (HHV-6) variants A and B are distinct viruses that differ in their biological properties and association to disease. Diagnostic tools able to discriminate between these two variants and between active or latent HHV-6 infection are much needed. In our effort to develop variant-specific antibodies against HHV-6 immediate-early (IE) proteins, we had previously generated P6H8, a monoclonal antibody (mAb) reacting specifically with the immediate-early 2 (IE2) proteins from HHV-6A.

OBJECTIVES

To characterize the P6H8 HHV-6 variant specific mAb and evaluate its potential as part of a variant-specific diagnostic tool for HHV-6A infection. Consequently, our objective was to map the epitope recognized by P6H8.

STUDY DESIGN

In order to map P6H8 reactivity by Western blotting, we generated deletion mutants of IE2 protein as well as various GST-IE2 fusion proteins. HHV-6A infected cells were used to demonstrate P6H8 reactivity against native IE2. A synthetic peptide corresponding to the P6H8 epitope was used to confirm our results and block P6H8 reactivity.

RESULTS

We mapped the P6H8 epitope to amino acids 1078-1089 of HHV-6A IE2. A peptide (FTPFYYQSSRTR) recreating this epitope was effective in blocking the recognition of both native and recombinant IE2 by P6H8.

CONCLUSIONS

Our work provides a precise characterization of the P6H8 mAb and its specificity toward the IE2 protein of HHV-6 variant A which could prove useful for the differential diagnostic of active infection by HHV-6.