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Human herpesvirus 6B (HHV-6B) belongs to the β-herpesvirus subfamily of the Herpesviridae. To understand capsid assembly and capsid-tegument interactions, here we report atomic structures of HHV-6B capsid and capsid-associated tegument complex (CATC) obtained by cryoEM and sub-particle reconstruction. Compared to other β-herpesviruses, HHV-6B exhibits high similarity in capsid structure but organizational differences in its CATC (pU11 tetramer). 180 "VΛ"-shaped CATCs are observed in HHV-6B, distinguishing from the 255 "Λ"-shaped dimeric CATCs observed in murine cytomegalovirus and the 310 "Δ"-shaped CATCs in human cytomegalovirus. This trend in CATC quantity correlates with the increasing genomes sizes of these β-herpesviruses. Incompatible distances revealed by the atomic structures rationalize the lack of CATC's binding to triplexes Ta, Tc, and Tf in HHV-6B. Our results offer insights into HHV-6B capsid assembly and the roles of its tegument proteins, including not only the β-herpesvirus-specific pU11 and pU14, but also those conserved across all subfamilies of Herpesviridae.

Nonpharmaceutical interventions (NPIs) to control COVID-19 have decreased the incidence of many pediatric infectious diseases. The epidemiology of β- and γ-herpesvirus infections might have been affected by NPIs. The aim of this study was to elucidate changes in trends in β- and γ-herpesvirus infections and complex febrile seizures (cFS) of viral etiology before and during the COVID-19 pandemic. Between April 2017 and March 2021, febrile children aged ≤5 years were enrolled. Detection of EBV, CMV, HHV-6B, and HHV-7 DNA in serum was performed using real-time PCR. The epidemiology of viral infections and cFS were compared between the prepandemic and pandemic periods. During the observation period, 1432 serum samples were collected. The mean number of febrile children decreased during the pandemic period, but the number of patients with HHV-6B infection increased from 35 (9.3% of all febrile children) per year before the pandemic to 43 (15.5%) during the pandemic. The change in the proportion of patients with primary HHV-6B infection was 6.50% (95% confidence interval [CI], 2.05%-11.3%; p = 0.0047). The mean number of patients with cFS decreased during the pandemic period, but the number of patients with HHV-6B-associated cFS was stable throughout the observation period. Therefore, the change in proportion of patients with cFS caused by primary HHV-6B infection was 49.5% (95% CI, 12.2%-60.5%; p = 0.0048). The disease burden of primary HHV-6B infection among patients in the emergency room remained unchanged, with a significant increase in the relative proportion after the COVID-19 pandemic began., (© 2023 Wiley Periodicals LLC.)

While hundreds of thousands of human whole genome sequences (WGS) have been collected in the effort to better understand genetic determinants of disease, these whole genome sequences have less frequently been used to study another major determinant of human health: the human virome. Using the unmapped reads from WGS of over 1000 families, we present insights into the human blood DNA virome, focusing particularly on human herpesvirus (HHV) 6A, 6B, and 7. In addition to extensively cataloguing the viruses detected in WGS of human whole blood and lymphoblastoid cell lines, we use the family structure of our dataset to show that household drives transmission of several viruses, and identify the Mendelian inheritance patterns characteristic of inherited chromsomally integrated human herpesvirus 6 (iciHHV-6). Consistent with prior studies, we find that 0.6% of our dataset's population has iciHHV, and we locate candidate integration sequences for these cases. We document genetic diversity within exogenous and integrated HHV species and within integration sites of HHV-6. Finally, in the first observation of its kind, we present evidence that suggests widespread de novo HHV-6B integration and HHV-7 integration and reactivation in lymphoblastoid cell lines. These findings show that the unmapped read space of WGS is a promising source of data for virology research., (© 2022. The Author(s).)

A number of studies have suggested that human herpesvirus 6A (HHV-6A) may play a role in multiple sclerosis (MS). Three possible hypotheses have been investigated: (1) U24 from HHV-6A (U24-6A) mimics myelin basic protein (MBP) through analogous phosphorylation and interaction with Fyn-SH3; (2) U24-6A affects endocytic recycling by binding human neural precursor cell (NPC) expressed developmentally down-regulated protein 4-like WW3* domain (hNedd4L-WW3*); and (3) MS patients who express Killer Cell Immunoglobulin Like Receptor 2DL2 (KIR2DL2) on natural killer (NK) cells are more susceptible to HHV-6 infection. In this contribution, we examined the validity of these propositions by investigating the interactions of U24 from HHV-6B (U24-6B), a variant less commonly linked to MS, with Fyn-SH3 and hNedd4L-WW3* using heteronuclear single quantum coherence (HSQC) nuclear magnetic resonance (NMR) titrations and isothermal titration calorimetry (ITC). In addition, the importance of phosphorylation and the specific role of U24 in NK cell activation in MS patients were examined. Overall, the findings allowed us to shed light into the models linking HHV-6 to MS and the involvement of U24.

Human roseolovirus U20 and U21 are type I membrane glycoproteins that have been implicated in immune evasion by interfering with recognition of classical and non-classical MHC proteins. U20 and U21 are predicted to be type I glycoproteins with extracytosolic immunoglobulin-like domains, but detailed structural information is lacking. AlphaFold and RoseTTAfold are next generation machine-learning-based prediction engines that recently have revolutionized the field of computational three-dimensional protein structure prediction. Here, we review the structural biology of viral immunoevasins and the current status of computational structure prediction algorithms. We use these computational tools to generate structural models for U20 and U21 proteins, which are predicted to adopt MHC-Ia-like folds with closed MHC platforms and immunoglobulin-like domains. We evaluate these structural models and place them within current understanding of the structural basis for viral immune evasion of T cell and natural killer cell recognition., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2022 Weaver, Arya, Schneider, Hudson and Stern.)

Background: We examined the correlation between persistent human herpesvirus 6 (HHV-6) DNAemia (p-HHV-6) and absolute lymphocyte count (ALC), platelet count (PLT), and all-cause mortality by 1 year after ex vivo T-cell-depleted (TCD) hematopoietic cell transplant (HCT)., Methods: We analyzed a cohort of adult TCD HCT recipients during 2012-2016 prospectively monitored for plasma HHV-6 by quantitative polymerase chain reaction from day +14 post-HCT through day +100 (D+100). p-HHV-6 was defined as ≥2 consecutive values of ≥500 copies/mL by D+100. PLT and ALC were compared between patients with and without p-HHV-6 using generalized estimating equations (GEE). Multivariable Cox proportional hazard models (PH) were used to identify the impact of p-HHV-6 on 1 year mortality., Results: Of 312 patients, 83 (27%) had p-HHV-6 by D+100. p-HHV-6 was associated with lower ALC and PLT in the first year post-HCT. In multivariable models, p-HHV-6 was associated with higher mortality by 1 year post-HCT (adjusted hazard ratio, 2.97 [95% confidence interval, 1.62-5.47]; P = .0005), after adjusting for age, antiviral treatment, and ALC at D+100., Conclusions: p-HHV-6 was associated with lower ALC and PLT in the first year post-HCT. p-HHV-6 was an independent predictor of mortality in the first year after TCD HCT., (© The Author(s) 2021. Published by Oxford University Press for the Infectious Diseases Society of America. All rights reserved. For permissions, e-mail: journals.permissions@oup.com.)

Purpose: The BioFire FilmArray® Meningitis/Encephalitis Panel (FAMEP) is designed to rapidly and accurately detect common multiple pathogens that cause central nervous system (CNS) infection, including viruses, bacteria, and yeast. The FAMEP's usefulness in the setting of allogeneic hematopoietic stem cell transplantation (HSCT) has not been fully evaluated. This retrospective study evaluated the usefulness of the FAMEP in the screening for CNS infection after allogeneic HSCT., Methods: Cerebrospinal fluid (CSF) was obtained from 12 patients to evaluate the causes of CNS disorders after allogeneic HSCT, and the FAMEP was applied., Results: The median day of the FAMEP evaluations was 27 days post-transplant (range, 0-390). Human herpesvirus 6 (HHV-6) was detected in three patients and cytomegalovirus was detected in one patient, leading to the diagnosis of encephalitis/myelitis. In three patients (HHV-6, n = 2; CMV, n = 1), the presence of the viruses was confirmed by conventional real-time polymerase chain reaction (PCR). However, in the remaining patient with HHV-6 detected by the AMEP, HHV-6 was not detected by real-time PCR at the onset but was detected 7 days later. The treatments for the detected viruses improved the clinical conditions in the four patients., Conclusions: Our results suggest that the FAMEP can be a useful sensitive assay in the screening and diagnosis of CNS viral infections after allogeneic HSCT., (© 2021. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

Background: Little is known about the kinetics and clinical significance of saliva human herpesvirus-6 (HHV-6) DNA after hematopoietic stem cell transplantation (HSCT)., Methods: In this observational study, we quantified HHV-6 DNA in serially collected plasma and saliva from allogeneic HSCT recipients. Associations between the status of salivary HHV-6 DNA and the development of HHV-6 encephalitis, depression, and oral mucosal graft-versus-host disease (GVHD) were retrospectively analyzed., Results: A total of 787 plasma and 434 saliva samples were collected from 56 patients. The cumulative incidence of HHV-6 DNA in plasma and saliva at 60 days after transplantation was 51.8% and 83.9%, respectively. The peak level of salivary HHV-6 DNA was significantly higher in patients who displayed plasma HHV-6 DNA than in those who did not (median, 51,584 copies/mL vs 587 copies/mL; P < .0001). Salivary HHV-6 DNA levels increased after positive plasma HHV-6 DNA was detected and remained high during observation period. Despite the frequent occurrence of positive salivary HHV-6 DNA, no patient developed depression. Positivity of salivary HHV-6 DNA was not significantly associated with the development of HHV-6 encephalitis (P = 1.00, Fisher's exact test) or oral mucosal GVHD (P = .71, Grey's test). No significant relationship between salivary HHV-6 DNA and these diseases was found even when comparing higher HHV-6 DNA loads in saliva., Conclusion: Salivary HHV-6 DNA levels increased after HHV-6 DNA was detected in the blood. However, no epidemiological evidence was shown to support a role of salivary HHV-6 in the development of HHV-6 encephalitis, depression, and oral mucosal GVHD., (© 2020 Wiley Periodicals LLC.)

Background: Human herpesvirus 6 (HHV-6) reactivation is relatively common after allogeneic hematopoietic stem cell transplantation (allo-HSCT). However, the incidence of HHV-6 reactivation and the clinical outcomes following unmanipulated haploidentical HSCT (haplo-HSCT) remain unknown., Method: We prospectively monitored blood HHV-6 DNA using real-time quantitative polymerase chain reaction weekly until day 100 post unmanipulated haplo-HSCT in patients with hematological malignancies., Results: From November 2016 to March 2017, 102 patients (58 male and 44 female, median age 25(2-58) years old) were enrolled. Within 100 days post-transplantation, 27 patients (27/136, 19.9%) developed HHV-6 viremia with a median onset time of 14 (7-98) days. The cumulative incidence of HHV-6 reactivation on day 100 post-HSCT was 25.5 ± 4.3% in haplo-HSCT. The median HHV-6 copy number was 1.45 × 10 3 (5.48 × 10 2 -2.00 × 10 4 ) copies/ml. The HHV-6 viremia duration time was 7 days in 23 patients, 14 days in one patient and 21 days in one patient. In multivariate analysis, prior HHV-6 reactivation was an independent risk factor for grade 2-4 graft-versus-host disease (GVHD). But it did not influence the overall survival (OS)(HR 1.624, 95%CI 0.768-3.432, P = .204), disease-free survival (DFS) (HR 1.640, 95%CI 0.799-3.367, P = .177) and non-relapse mortality (NRM) (HR 1.644, 95%CI 0.670-4.038, P = .278)., Conclusion: The reactivation of HHV-6 after unmanipulated haploidentical transplantation predicts the occurrence of grade 2-4 a-GVHD, but it may not influence the overall survival (OS), disease-free survival (DFS) and non-relapse mortality (NRM)., (© 2020 Wiley Periodicals LLC.)

Human herpesvirus 6B (HHV-6B) encephalitis in a liver transplant recipient is rarely reported. In this report, we presented a case of HHV-6B encephalitis in a liver transplant recipient and reviewed the relevant literature. A 56-year-old man was admitted to the intensive care unit (ICU) with an acute headache and intermittent convulsion 17 days after liver transplantation. Next-generation sequencing (NGS) of the cerebrospinal fluid (CSF) revealed 30691 sequence reads of HHV-6B and real-time polymerase chain reaction (real-time PCR) of the CSF detected HHV-6B DNA at 12 000 copies/mL, so the patient was diagnosed with HHV-6B encephalitis and received ganciclovir treatment promptly. The condition of the patient improved well and returned to the general ward with no neurologic deficits. This case indicated that adequate awareness, early diagnosis, and timely treatment are crucial to a good prognosis of HHV-6B encephalitis after liver transplantation., (© 2020 The Authors. Transplant Infectious Disease published by Wiley Periodicals LLC.)

Background: Reactivation of human herpesvirus 6 (HHV-6) occurs in 30%-50% of patients (pts) who receive allogeneic (allo) hematopoietic stem cell transplant (HCT). However, the recommendation for post-transplant HHV-6 monitoring and treatment in pediatric pts is not well established., Methods: HHV-6 incidence rates and the clinical outcomes were reported for 139 pediatric pts (≤18 years) undergoing first allo-HCT at City of Hope from July 2011 to July 2017, for whom HHV-6 was monitored weekly throughout HCT hospitalization. For 57 pediatric pts, who underwent first HCT from January 2009 to July 2011, HHV-6 was tested as clinically indicated and only rates of HHV-6 viremia were collected., Results: From July 2011 to July 2017, HHV-6 was detected in 88/139 pts (63%). The frequency of HHV-6 viremia was associated with malignant diagnoses, myeloablative conditioning, and cord blood HCT. Treatment with antiviral agents was offered to symptomatic pts with a higher viral load (VL), for whom the time to VL clearance was longer and the frequency of subsequent recurrences was higher. Pts with a lower VL cleared HHV-6 without treatment. HHV-6 viremia was associated with a higher frequency of grade II-IV acute graft-versus-host disease (GVHD) (P = .022), but did not affect overall survival (OS), disease-free survival (DFS), non-relapsed mortality (NRM), myeloid, or platelet (Plt) engraftment., Conclusions: HHV-6 weekly screening is not necessary for all HCT pts but may be considered for high-risk pts with malignant diagnoses undergoing cord blood HCT; otherwise, HHV-6 should be tested as clinically indicated. Only symptomatic pts (especially with a high VL > 25 000) could benefit from treatment. HHV-6 viremia at the time of initiation and administration of the conditioning regimen cleared promptly without the need to augment the transplant process., (© 2020 Wiley Periodicals LLC.)

The majority of adults are seropositive for human herpesvirus 6 (HHV-6). HHV-6 reactivation can occur after allogeneic hematopoietic stem cell transplantation (HSCT) and lead to life-threatening central nervous system disorders. In this prospective study, we evaluated the relationship between HHV-6 reactivation and anti-HHV-6 IgG antibody levels in recipients of allogeneic HSCT. The HHV-6 viral load in the plasma was quantitatively measured weekly after allogeneic HSCT by real-time polymerase chain reaction. The level of anti-HHV-6 IgG antibody was measured by enzyme-linked immunosorbent assay before and serially after transplantation. In 28 of the 56 evaluated patients (50%), HHV-6 reactivation was detected after transplantation. In a multivariate analysis, cord blood as the stem cell source was the only significant factor associated with HHV-6 reactivation (odds ratio, 8.6; 95% confidence interval, 2.3 to 32.6; P < .01). When evaluated in the recipients of cord blood transplantation (CBT), the anti-HHV-6 antibody level before transplantation was significantly lower in the patients with HHV-6 reactivation compared with those without (sample positivity index: median, 2.04 [range, 0.95 to 5.98] versus 4.15 [range, 3.93 to 5.65]; P < .05). The anti-HHV-6 antibody level was significantly decreased at 3 months post-transplantation compared with before transplantation (P < .01). Such differences were not observed in other stem cell sources. Our results demonstrate that the low anti-HHV-6 antibody level before transplantation was associated with the reactivation of HHV-6 after CBT, and that the anti-HHV-6 antibody level was significantly decreased specifically after CBT. These results suggest that HHV-6-specific humoral immunity plays a role in HHV-6 reactivation after CBT., (Copyright © 2020 The American Society for Transplantation and Cellular Therapy. Published by Elsevier Inc. All rights reserved.)

Human herpesvirus 6 (HHV-6) encephalitis has a high mortality rate. Among those who survive, ~80% develop some type of permanent neurologic disorder. Early diagnosis and treatment may help prevent long-term sequelae. There have been several case reports as well as retrospective and prospective studies associating HHV-6 encephalitis with some form of sodium imbalance, either hyponatremia or hypernatremia; however, the exact frequency post-HCT is unknown, with reports ranging from 30% to 100%. We performed a systematic review of the literature and found 34 cases of HHV-6 encephalitis reported in conjunction with sodium imbalance that documented the timing of that imbalance relative to the onset of encephalitis. Sodium imbalance occurred before or at the onset of HHV-6 encephalitis in all but 2 cases (94%). This finding supports previous suggestions that sodium imbalance can be considered an early indicator of the potential development or presence of HHV-6 encephalitis in at-risk patient populations., (Copyright © 2020 American Society for Transplantation and Cellular Therapy. Published by Elsevier Inc. All rights reserved.)

A 46-year-old female patient underwent a cord blood transplantation (conditioning regimen: fludarabine/busulfan4/melphalan80; graft-versus-host disease (GVHD) prophylaxis: tacrolimus + mycophenolate mofetil) for acute myeloid leukemia (AML) with her 1st hematological complete response to induction therapy (idarubicin 3 days+cytarabine 7 days). She lost her consciousness due to human herpesvirus 6 (HHV-6) encephalitis on day 31, and therefore, we increased the foscarnet dosage (from 120 mg/kg to 180 mg/kg). Her consciousness level improved after treatment. However, 8 hours of sudden hypothermia occurred with hyperhidrosis, hypertension, and subsequent hyperglycemia on day 34. Her condition did not improve even after administration of anticonvulsant, steroid pulse, or intravenous immunoglobulin. A total of 75 attacks were observed until she was discharged on day 471. She has not shown chronic GVHD or relapsed AML since then. However, HHV-6 caused prolonged damage to her hypothalamus as observed through magnetic resonance imaging (MRI) and single-photon emission computed tomography (SPECT) using 99m Tc ethyl cysteinate dimer even when the virus was not detected from her cerebrospinal fluid. This damage can be responsible for the hypothermia attacks. This is the first case report of prolonged series of hypothermia attacks for over a year as a sequela of HHV-6 encephalitis after a cord blood transplantation for AML.

Human herpesvirus (HHV)-6B encephalitis has been increasingly recognized as an important central nervous system (CNS) complication after allogeneic hematopoietic stem cell transplantation. In this review, the best way to diagnose and treat this devastating complication is described. Diagnostic pitfalls: HHV-6B encephalitis should be diagnosed based on the presence of CNS symptoms, positive results for HHV-6 DNA in the cerebrospinal fluid (CSF), and exclusion of other causes of CNS symptoms. There are potential pitfalls when diagnosing HHV-6B encephalitis. Moreover, false-positive detection of HHV-6 DNA in the CSF can occur. Pleocytosis is observed in few patients, and CSF protein levels are often normal. Limbic encephalitis findings are not commonly detected through a brain MRI at the time of development. Prevention: Neither routine monitoring nor routine prophylactic antiviral therapy is recommended to prevent the development of HHV-6B encephalitis. Treatment: Empiric therapy should be started immediately after HHV-6B encephalitis is suspected. The Guideline Committee of the JSHCT recommends full-dose foscarnet (180 mg/kg/day) for the treatment of HHV-6B encephalitis. Therapeutic effect of anti-HHV6 therapy is assessed based on CNS symptoms and HHV-6 DNA in the CSF, which should be evaluated 1-2 weeks after initiating treatment. Even in patients exhibiting good therapeutic effects, antiviral treatment should be continued for at least 3 weeks.

In this retrospective analysis using the Transplant Registry Unified Management Program, we identified 145 patients with human herpesvirus (HHV)-6 encephalitis among 6593 recipients. The cumulative incidences of HHV-6 encephalitis at 100 days after transplantation in all patients, recipients of bone marrow or PBSCs and recipients of cord blood were 2.3%, 1.6% and 5.0%, respectively. Risk factors identified in multivariate analysis were male sex, type of transplanted cells (relative risk in cord blood transplantation, 11.09, P<0.001; relative risk in transplantation from HLA-mismatched unrelated donor, 9.48, P<0.001; vs transplantation from HLA-matched related donor) and GvHD prophylaxis by calcineurin inhibitor alone. At 100 days after transplantation, the overall survival rate was 58.3% and 80.5% among patients with and without HHV-6 encephalitis, respectively (P<0.001). Neuropsychological sequelae remained in 57% of 121 evaluated patients. With both foscarnet and ganciclovir, full-dose therapy (foscarnet ⩾180 mg/kg, ganciclovir ⩾10 mg/kg) was associated with better response rate (foscarnet, 93% vs 74%, P=0.044; ganciclovir, 84% vs 58%, P=0.047). HHV-6 encephalitis is not rare not only in cord blood transplant recipients but also in recipients of HLA-mismatched unrelated donors. In this study, development of HHV-6 encephalitis was associated with a poor survival rate, and neurological sequelae remained in many patients.

Human herpesvirus-6 (HHV-6) encephalitis and myelitis following allogeneic hematopoietic stem cell transplantation (HSCT) is frequently life-threatening. We retrospectively evaluated the clinical significance of hyponatremia in cases of HHV-6 encephalitis/myelitis. Using an institutional database and medical records, we identified and retrospectively analyzed 16 cases of HHV-6 encephalitis and/or myelitis after allogeneic HSCT. HHV-6 encephalitis and myelitis were defined as the symptoms/signs with HHV-6-DNA in the cerebrospinal fluid. Seizure and memory disorder were defined as symptoms/signs of encephalitis, and dysesthesia and vesicorectal disorder as those of myelitis. Five patients developed encephalitis with or without myelitis, and 11 patients developed myelitis alone. Hyponatremia (median 129.1 mEq/L; range 125.9-130.1) was observed in all five patients with HHV-6 encephalitis at diagnosis, and values were significantly lower than those in patients with HHV-6 myelitis alone (median 137.6; range 134.0-142.2; P < 0.01). In three of the five patients with encephalitis, the decrease in sodium level preceded the clinical onset of encephalitis by one or two days. These results suggest that hyponatremia may be an important manifestation of HHV-6 encephalitis, but not of myelitis, and could be a useful tool for the early prediction or diagnosis of HHV-6 encephalitis.

Competing Interests: Conflict-of-interest disclosure: The author declares no competing financial interests.

Objective: To investigate the clinical significance of PCR detection of human herpesvirus 6 (HHV6) in gastro biopsy on the course of diarrhea in patients with severe diarrhea after allogeneic hematopoietic stem cell transplantation (HSCT) . Methods: Data from a cohort of 45 HSCT recipients (including age, sex, transplantation conditions, graft-versus-host disease, treatments, clinical signs, outcome, HHV6, and other infections) performed between 2015 and 2016 were collected. Univariate analysis was used to evaluate influences between the different parameters. Results: Of the 45 enrolled recipients, 21 patients (46.7%) presented HHV6 positive in gastro-biopsy during the analyzed period. The incidence of CMV viremia in the positive HHV6 group was comparable with that in the negative HHV6 group. But the incidence of EBV viremia in the positive HHV6 group was significantly higher than in the negative HHV6 group ( P =0.028) . 44 out of 45 patients with severe diarrhea were given antiviral treatment with foscarnet and/or ganciclovir, the latter didn't influence the course of the diarrhea. Conclusions: Positive PCR results in GI tract samples didn't necessarily reflect reactivation of HHV6. Further studies are needed to define the significance of HHV6 for GI tract symptoms after allo-HSCT.

A 26-year-old, otherwise healthy man presented with visual abnormality followed by loss of consciousness and convulsion. The patient then developed headache and fever 14 days later. Brain MRI showed hyperintensities in the left cingulate cortex. The cerrebrospinal fluid examinations showed mononuclear pleocytosis and positive PCR results for human herpesvirus 6 (HHV-6). A diagnosis of HHV-6 encephalitis and symptomatic epilepsy was made. The patient's clinical symptoms improved promptly following acyclovir treatment. However, 3 months later the patient noticed dysesthesia in the trunk, the left upper limb and the right lower limb. Brain and spine MRI showed multiple brain white matter lesions, the middle cerebellar peduncle and cervical spinal lesions. The symptoms resolved following methylprednisolone pulse therapy only. We report an adult patient with HHV-6 encephalitis followed by acute disseminated encephalomyelitis whose initial presentation was epilepsy. HHV-6 encephalitis should be included in the differential diagnosis of encephalitis of unknown etiology in an immunocompetent adult.

We present a case report of a meningoradiculopathy associated with human herpesvirus 7, with long-term motor neurologic sequelae. It is important to consider human herpesvirus 7 as a potential pathogen of severe neurologic disease and sequelae in immunocompetent children, especially in older patients presenting neurologic signs.

Multiple sclerosis (MS) is a multifactorial disease resulting from complex interactions between predisposing genetic and environmental factors. Among the many potential environmental risk factors, several common infectious agents such as Epstein-Barr virus (EBV), human herpesvirus-6 and Chlamydia pneumoniae(C. pneumoniae) have been causatively implicated in the onset of MS. However, with the exception of EBV, consistent data are yet to be obtained regarding the involvement of infectious agents. With respect to the Japanese population, we found that EBV infection is a risk factor for the subgroup of Japanese MS patients not harboring the HLA-DRB1*0405 allele, a known genetic risk factor for MS in this ethnic group. By contrast, bacterial infections such as Helicobacter pylori and C. pneumoniae are risk factors for Japanese neuromyelitis optica, especially in patients with anti-aquaporin 4 antibodies.

Primary human herpesvirus 6(HHV-6) and HHV-7 infections cause exanthem subitum. The disease is common febrile illness in infants, indeed these viruses rarely cause encephalopathy. Recently, various types of encephalopathy have been reported in the patient with HHV-6. Therefore, appropriate treatment should be developed for each type of the encephalitis. Recent data suggest that HHV-6 reactivation is associated with encephalitis, which occurred in immunocompromised patients. Typical clinical features of HHV-6 encephalitis in transplant recipients were amnesia and MRI findings in the hippocampus. Thus, HHV-6 is considered to be etiological agent for post-transplant acute limbic encephalitis. It has been suggested that either ganciclovir or foscarnet has anti-viral effect against HHV-6 in vitro. Therefore either of the two anti-viral drugs might be useful for treatment of HHV-6 encephalitis.

Human herpesvirus 6 is a ubiquitous Herpesviridae infecting patients during childhood. Its role in ocular disorders is mostly unknown. We report the case of a 47-year-old woman with a history of rheumatoid arthritis (treated with etanercept) and tuberculosis, who presented with sudden unilateral panuveitis. The patient was initially treated with ganciclovir, as the polymerase chain reaction in the aqueous humor was positive for HHV6, and with pyrimethamine and sulfadiazine because a toxoplasmic co-infection was highly suspected, which was biologically confirmed. Management of HHV6 in a nervous system disorder is challenging because its replication has been proved but its role remains unclear. HHV6 may be pathogenic by itself but can facilitate co-infection as can etanercept., (Copyright © 2010 Elsevier Masson SAS. All rights reserved.)

Human herpesvirus 6 (HHV-6) and CMV reactivation were monitored in a cohort of 72 consecutive haematopoietic stem cell transplant (HSCT) patients using RQ-PCR and antigenaemia assay, respectively. The association between acute GVHD (aGVHD) and HHV-6B/CMV was evaluated. We found that on day 100 the cumulative incidence of grades I-IV aGVHD, grades II-IV aGVHD and grades III-IV aGVHD was 55.6, 27.8 and 13.9%, respectively. Multivariate analysis indicated that HHV-6B reactivation was closely correlated with a higher probability of grade II-IV aGVHD by day 30 (Hazard ratio (HR), 8.9; 95% confidence interval (CI), 2.6-31.0; P=0.0006), by day 50 (HR, 6.1; 95% CI, 2.1-17.8; P=0.0010) and by day 100 (HR, 4.8; 95% CI, 1.7-13.6; P=0.0028). However, CMV reactivation did not significantly affect the development of aGVHD by day 50 (HR, 0.8; 95% CI, 0.1-6.7; P=0.8236) and by day 100 (HR, 0.5; 95% CI, 0.1-4.4; P=0.5330) after HSCT. In conclusion, this study demonstrated that active HHV-6B infection, but not CMV, is significantly associated with an increased risk of aGVHD development after HSCT.

Angioimmunoblastic T-cell lymphoma (T-AIL) is a peripheral T-cell lymphoma of unknown etiology. Previous clonality studies have shown a heterogeneous composition of this disease with varying restrictions of B- and T-cell populations in the tumour. For the first time in a single study and in the same pathological materials, we have analysed, lymphoid cell clonality and occurrence of human herpes viruses and Epstein Barr virus. Of 18 cases 12 (66.6%) had clonal T- and three (16.6%) had clonal B-cells. Presence of the lymphotropic viral genome of HHV6 was detected in four of 18 lymph node biopsies from T-AIL patients (22%), all were TCRgamma clonal. No HHV8 were found. Epstein Barr genome was found in 40% of cases. There was no significant association between T-cell clonality and HHV-6 or EBV infection, or between B-cell clonality and any virus infection. We conclude that T-AIL is a biologically and clinically heterogeneous entity whose true nature remains to be clarified., (Copyright 2005 John Wiley & Sons, Ltd)

When a six year-old immunocompetent child affected by encephalitis was subjected to virological studies, human herpesvirus 6 variant B2 resulted to be the cause of illness. Laboratory diagnosis based on the finding of human herpesvirus 6 genome in the cerebrospinal fluid of the patient both at the beginning of the disease and on the occasion of a relapse which occurred forty days after the patient's hospital discharge. The presence of high-avidity IgG to human herpesvirus 6 detected in the patient's serum at the time of the first hospital admission proved that he had suffered from a past infection by human herpesvirus 6. In the consequence of this, the human herpesvirus 6 DNA finding in the patient's cerebrospinal fluid was to ascribed to virus reactivation. In the light of virological and serological results, the clinical case described underlines the ability of human herpesvirus 6 to cause neurological disorders not only during primary infections but also during infections supported by rescued virus.

Objective: To study the infection of human herpesvirus 6(HHV-6) in NPC and its role in the carcinogensis of NPC., Methods: By using polymerase chain reaction (PCR) and in situ hybridization (ISH) HHV-6 and EBV DNA to from the paraffin-embedded tissues of normal nasopharynx precancerous nasopharynx and nasopharyngeal carcinoma. EBV LMP1 was also detected in 36 tissues of NPC by immunohistochemistry (IHC)., Results: HHV-6 DNA PCR were detected in 30.9% (13/42) of tissues of NPC, 4.7% (1/21) of precancerous nasopharynx and non in the normal nasopharynx. Within the same tissues, EBV DNA positive rates were 95.2% (40/42), 66.6% (14/21) and 25.9% (7/27), respectively. By using ISH, HHV-6 DNA were detected only in 11 NPC tissues out of 13 HHV-6 DNA positive NPC cases and EBV DNA were detected in 47.6% (10/21) of precancerous nasopharynx tissues and 85.7% (36/42) of NPC cases. EBV LMP1 expression were detected in 47.2% (17/36) of NPC tissues., Conclusion: NPC tissues can be infected with both HHV-6 and EBV, HHV-6 infection is correlated with the expression of EBV LMP1, suggesting that HHV-6 plays a direct/or indirect role in carcinogenesis of NPC via upregulating the expression of EBV LMP1.