Human Herpesvirus 6 DNA Research Articles

Valganciclovir for Suppression of Human Herpesvirus–8 Replication: A Randomized, Double‐Blind, Placebo‐Controlled, Crossover Trial

Human herpesvirus-8 (HHV-8) replication is critical in the induction and maintenance of Kaposi sarcoma, primary effusion lymphoma, and some cases of Castleman disease. In vitro and observational studies suggest that ganciclovir inhibits HHV-8 replication, but no randomized clinical trials have been conducted. A total of 26 men infected with HHV-8 were randomized to receive 8 weeks of valganciclovir administered orally (900 mg once per day) or 8 weeks of placebo administered orally. After a 2-week washout period, participants in each group received the study drug they had not yet taken (either valganciclovir or placebo), for 8 additional weeks. Oral swab samples were collected daily during the study, and HHV-8 and CMV DNA were quantified by real-time PCR. A total of 16 human immunodeficiency virus (HIV)-positive men and 10 HIV-negative men enrolled in and completed the study. Of the 3,439 swab samples that participants had been expected to provide, 3029 (88%) were available for analysis. HHV-8 was detected on 44% of swabs collected from participants who were receiving placebo, compared with 23% of swabs collected from participants who were receiving valganciclovir (relative risk [RR], 0.54 [95% confidence interval {CI}, 0.33-0.90]; P = .02). Valganciclovir reduced oropharyngeal shedding of cytomegalovirus by 80% (RR, 0.20 [95% CI, 0.08-0.48]; P < .001). Shedding of HHV-8 and shedding of cytomegalovirus were independent. Hematologic, renal, or hepatic toxicities were no more common among participants who received the active drug, compared with those who received placebo, though participants who received valganciclovir reported more days of diarrhea. Valganciclovir administered orally once per day is well tolerated and significantly reduces the frequency and quantity of HHV-8 replication.

Combined Cytomegalovirus Prophylaxis in Lung Transplantation: Effects on Acute Rejection, Lymphocytic Bronchitis/Bronchiolitis, and Herpesvirus Infections

Lung transplantation recipients are at high risk for herpesvirus infections. We evaluated the effect of combined cytomegalovirus (CMV) prophylaxis on CMV pneumonia, acute rejection episodes (ARE), lymphocytic bronchitis/bronchiolitis (LB), and obliterans bronchiolitis (OB) diagnosed in 180 transbronchial biopsies (TBB) of lung transplant recipients. At our center, 25 patients (control group; 1999–2002) received acyclovir for 12 months and 21 recipients (study group; 2003–2007) received combined CMV prophylaxis consisting of CMV-IG (Cytotect Biotest) for 12 months and ganciclovir or valganciclovir from postoperative day 21 for 3 weeks. Among the study group (since 2005), CMV shell vial viral culture and Epstein-Barr virus (EBV), human herpesvirus-6 (HHV-6), and HHV-7 DNA were determined on BAL specimens. In the study group, the number of LB was significantly lower than in the control group (2% vs 11%; P = .04). Similar results were obtained for ARE (6% vs 17%; P = .04). No difference was observed in OB (5% vs 5%; P = .53, NS). A reduction trend was found in CMV pneumonia (2% vs 7%; P = .23, NS). Logistic regression analysis showed a relationship between prophylaxis and a reduced prevalence of ARE (odds ratio [OR] 3.25, confidence interval [CI] 1.12–9.40; P = .03). Finally, in the study group, BAL EBV-DNA positivity and EBV-CMV coinfections were low (6% and 0%, respectively) compared with other herpesviruses and with the literature. Our data suggested the efficacy of combined CMV prophylaxis to prevent ARE and LB, 2 risk factors for chronic rejection, and a possible role to reduce the trend toward CMV pneumonia and EBV infections.

Predicting the evolution of Kaposi sarcoma, in the highly active antiretroviral therapy era

The outcome of Kaposi sarcoma varies. While many patients do well on highly active antiretroviral therapy, others have progressive disease and need chemotherapy. In order to predict which patients are at risk of unfavorable evolution, we established a prognostic score. The survival analysis (Kaplan-Meier method; Cox proportional hazards models) of 144 patients with Kaposi sarcoma prospectively included in the Swiss HIV Cohort Study, from January 1996 to December 2004, was conducted. OUTCOME ANALYZED: use of chemotherapy or death. VARIABLES ANALYZED: demographics, tumor staging [T0 or T1 (16)], CD4 cell counts and HIV-1 RNA concentration, human herpesvirus 8 (HHV8) DNA in plasma and serological titers to latent and lytic antigens. Of 144 patients, 54 needed chemotherapy or died. In the univariate analysis, tumor stage T1, CD4 cell count below 200 cells/microl, positive HHV8 DNA and absence of antibodies against the HHV8 lytic antigen at the time of diagnosis were significantly associated with a bad outcome. Using multivariate analysis, the following variables were associated with an increased risk of unfavorable outcome: T1 [hazard ratio (HR) 5.22; 95% confidence interval (CI) 2.97-9.18], CD4 cell count below 200 cells/microl (HR 2.33; 95% CI 1.22-4.45) and positive HHV8 DNA (HR 2.14; 95% CI 1.79-2.85). We created a score with these variables ranging from 0 to 4: T1 stage counted for two points, CD4 cell count below 200 cells/microl for one point, and positive HHV8 viral load for one point. Each point increase was associated with a HR of 2.26 (95% CI 1.79-2.85). In the multivariate analysis, staging (T1), CD4 cell count (<200 cells/microl), positive HHV8 DNA in plasma, at the time of diagnosis, predict evolution towards death or the need of chemotherapy.

Detection and quantitative analysis of human herpesvirus in pilocytic astrocytoma

We investigated the hypothetical role of human herpesviruses (HHVs) in tumour formation of the cerebellum. Thirty-five samples of pilocytic astrocytoma and 10 control samples of cerebellum from patients who died of unrelated diseases were examined. Presence of the 8 known HHVs was first studied using specific real-time quantitative Polymerase Chain Reaction (qPCR) targeting viral DNA polymerase. HHV's DNA polymerase was found present in 20 samples (7 controls, 13 astrocytomas) and was absent in 25 samples (3 controls, 22 astrocytomas). DNA polymerase of Epstein–Barr Virus (EBV) was present in 16 samples, 7/10 controls (70%) and 9/35 astrocytomas (26%). HHV-1 and Varicella–Zoster virus were detected only twice and HHV-2, Cytomegalovirus, HHV-7 and HHV-8, only once. HHV-6 was not detected. In all cases, the gene copy numbers of DNA polymerase were low (< 100/100 ng DNA). A second approach was to search for novel HHVs, using consensus- degenerated hybrid oligonucleotide primers (CODEHOP) PCR: no sequence indicative of a new HHV was detected. In summary, EBV was the most frequent HHV detected in pilocytic astrocytoma, but at very low levels. According to the actually accepted threshold the results suggest that EBV cannot be considered responsible for tumorigenesis of pilocytic astrocytoma.

DNA microarray technology for simultaneous detection and species identification of seven human herpes viruses

The aim of the study was to develop a multiplex PCR-based DNA microarray technology for simultaneous detection and species identification of seven human herpes viruses, namely herpes simplex virus type 1, type 2 (HSV-1, HSV-2), varicella-zoster virus (VZV), Epstein-Barr virus (EBV), cytomegalovirus (CMV), and human herpes virus 6 (HHV-6A, HHV-6B), and to apply this technology to accurate diagnosis of herpesvirus-associated diseases. Primers and oligonucleotide probes were designed and synthesized based on the highly conserved regions of the DNA polymerase gene in human herpes viruses. DNA microarrays were made by printing the oligonucleotide probes onto special glass slides. After amplification and labeling with CY5, the PCR products were hybridized with the DNA microarrays and species identified. Sixty-one cerebrospinal fluid (CSF) and 132 blood specimens were analyzed by this technique, and the results were compared with those of TaqMan PCR. Several specimens were sequenced further after cloning. The PCR products of the seven human herpes viruses ranged from 224 to 252 bp, and could be species identified with DNA microarrays. The detection limits were 10(1) copies/microl for each virus. And the test showed no cross-reaction to DNA extracted from S. aureus, E. coli, hepatitis B virus, Cryptococcus neoformans, Candida albicans and human genome. Among 132 blood and 61 CSF specimens, 55 were tested positive for human herpes virus DNA. Compared with the results of TaqMan PCR, the sensitivity and specificity of the DNA microarray technology was 96.2% and 99.3%, respectively. This multiplex PCR-based DNA microarray technology, which is rapid, specific and sensitive, serves as an effective technique for simultaneous detection and species identification of seven human herpes viruses.

Detection of human herpesvirus-6, Epstein-Barr virus and cytomegalovirus in formalin-fixed tissues from sudden infant death: A study with quantitative real-time PCR

Background The role of viruses in the context of sudden infant death in early childhood is still unclear, although there are many findings pointing to a viral infection possibly leading to death. Objectives To analyse the prevalence and viral loads of human herpesvirus-6 (HHV-6), Epstein-Barr virus (EBV), and cytomegalovirus (CMV), three viruses that have been previously detected in some cases of sudden death in infants, in tissues from sudden infant death syndrome (SIDS) patients and controls. Materials and methods Thirty-nine formalin-fixed paraffin-embedded tissue sections of eleven consecutive cases of SIDS, and thirty-nine formalin-fixed paraffin-embedded tissue sections of nine control cases were analysed by a specific quantitative real-time PCR for the detection of HHV-6, EBV, and CMV. Results The comparison of the whole viral DNA prevalence in cases and tissue sections between SIDS and controls showed a statistical significance (72.7% vs. 22.2%, p = 0.025; 41.1% vs. 10.3%, p = 0.001, respectively); in particular, we found a statistical significant difference for the EBV DNA prevalence among cases ( p = 0.042) and tissues ( p = 0.048), and a statistical significant difference for the HHV-6 DNA prevalence among cases ( p = 0.017). Conclusions This is one of the first studies using quantitative real-time PCR for virus detection in cases of SIDS, and the results suggest that some herpesvirus infections, and particularly those caused by EBV and HHV-6 could be related with some cases of SIDS. Further studies will be necessary to understand the real significance of these findings in the context of SIDS.

Use of multiplex PCR and real-time PCR to detect human herpes virus genome in ocular fluids of patients with uveitis

Aim:To measure the genomic DNA of human herpes viruses (HHV) in the ocular fluids and to analyse the clinical relevance of HHV in uveitis.Methods:After informed consent was obtained, a total...

Effect of phosphorylation on the transactivation activity of Epstein–Barr virus BMRF1, a major target of the viral BGLF4 kinase

Modification of human herpesvirus DNA polymerase processivity factors (PFs) by phosphorylation occurs frequently during viral lytic replication. However, functional regulation of the herpesvirus PFs through phosphorylation is not well understood. In addition to processivity, the PF BMRF1 of Epstein-Barr virus can function as a transactivator to activate the BHLF1 promoter within the lytic origin of replication (oriLyt), which is assumed to facilitate DNA replication through remodelling viral chromatin structure. BMRF1 is known to be phosphorylated by the viral BGLF4 kinase, but its impact on BMRF1 function is unclear. Seven candidate BGLF4 target sites were predicted within a proline-rich region between the DNA-processivity and nuclear-localization domains of BMRF1. We show that four of these residues, Ser-337, Thr-344, Ser-349 and Thr-355, are responsible for the BGLF4-induced hyperphosphorylation of BMRF1. In functional analyses, a phosphorylation-mimicking mutant of BMRF1 shows similar nuclear localization, as well as DNA-binding ability, to the wild type; however, it displays stronger synergistic activation of the BHLF1 promoter with Zta. Notably, BGLF4 downregulates BMRF1 transactivation and enhances the transactivation activity of Zta and the synergistic activation of BMRF1 and Zta on the BHLF1 promoter. Our findings suggest that BGLF4 may modulate the activation of the oriLyt BHLF1 promoter coordinately through multiple mechanisms to facilitate optimal oriLyt-dependent viral DNA replication.

Relationship among human herpesvirus 6 reactivation, serum interleukin 10 levels, and rash/graft-versus-host disease after allogeneic stem cell transplantation

The relationship between herpesvirus reactivation and graft-versus-host disease (GVHD) after allogeneic stem cell transplantation (allo-SCT) is unclear. We sought to examine the relationship between human herpesvirus (HHV) reactivation and rash/GVHD after allo-SCT by prospective evaluation. Fifteen patients who had received allo-SCT underwent prospective serial examinations for human herpesvirus 6 (HHV-6), HHV-7, cytomegalovirus, and Epstein-Barr virus DNA in the blood by polymerase chain reaction and real-time polymerase chain reaction. Serum interferon gamma, interleukins 4 and 10, tumor necrosis factor alpha, and soluble interleukin 2 receptor (sIL-2R) were also measured. In 10 of 15 patients, macular/papular eruptions were seen after allo-SCT and GVHD was diagnosed. In 8 patients with rash, HHV-6 DNA levels correlated with the cutaneous manifestation. Interleukin 10 and sIL-2R also increased in association with rash. The number of patients in our study was relatively small. Not all patients were examined for cytokines and sIL-2R. HHV-6 reactivation may be involved in the pathogenesis of rash/GVHD after allo-SCT.

High prevalence of Human Herpes Virus 8 (HHV-8) in patients with Warthin's tumors of the salivary gland

Background Warthin's tumor is a common benign neoplasm of the salivary gland. Human Herpes Virus 8 (HHV-8) is the etiologic agent for all forms of Kaposi's sarcoma (KS), and HHV-8 DNA is present in saliva, suggesting that non-sexual transmission is associated with latent infection of the salivary gland. Objectives To provide insights into the HHV-8 cell tropism, the presence of HHV-8 was investigated in a series of Warthin's tumors of the salivary gland and corresponding adjacent normal tissue. Study design Forty-three patients with Warthin's tumors (cystadenolymphoma) were tested for the presence of HHV-8 DNA, and corresponding adjacent normal tissue samples were obtained from 15 patients. DNA was extracted from the paraffin-embedded tissues. A nested polymerase chain reaction (PCR) assay was applied, and the positive samples were confirmed by direct sequencing. Results HHV-8 DNA was detected in 19 out of 43 (44%) salivary gland tumor samples. Among the 15 cases with paired samples, 9 were HHV-8-positive for both samples, 4 were HHV-8-negative for both samples while in two cases HHV-8 was detected only in the tumor specimens. Conclusions HHV-8 is frequently detected in adenoid salivary neoplasms, suggesting a significant role of the virus in the etiopathogenesis of the disease. Larger studies are required to investigate the role of HHV-8 in the development or progression of Warthin's tumors.

Toxic Epidermal Necrolysis Due to Zonisamide Associated With Reactivation of Human Herpesvirus 6

Recently, human herpesvirus 6 (HHV-6) reactivation has been frequently observed in patients with drug-induced hypersensitivity syndrome or drug rash with eosinophilia and systemic symptoms but not in patients with other types of drug eruptions, eg, Stevens-Johnson syndrome and toxic epidermal necrolysis (TEN). This finding suggests that there is a close relationship between HHV-6 reactivation and drug-induced hypersensitivity syndrome. A 71-year-old man who was not immunocompromised developed TEN because of zonisamide therapy. After the onset of the rash, significant increases in HHV-6 IgG titers and HHV-6 DNA levels were observed in the patient's whole blood samples, indicating that an HHV-6 reactivation had occurred. Furthermore, the patient's clinical manifestations of TEN appeared to recur concurrently with HHV-6 reactivation. Conclusion Our case suggests that HHV-6 reactivation may also occur in several types of drug eruptions, including Stevens-Johnson syndrome and TEN.

Characterization of a cidofovir-resistant HHV-6 mutant obtained by in vitro selection

Cidofovir (CDV) was used for in vitro selection of a human herpesvirus 6 (HHV-6) mutant with decreased susceptibility to this drug. The resulting mutant was highly resistant to CDV as compared to its sensitive counterpart (inhibitory concentration 50% (IC 50): 213 μM versus 1.8 μM). Its replication fitness was not impaired. Genotypic characterization of the resistant virus revealed a mutation in the U38 gene encoding the viral DNA polymerase. The resulting R798I amino acid change was located in the conserved domain VII close to the highly conserved motif KKRY interacting with the DNA primer–template duplex, and is likely responsible for the high-level resistance to CDV, even though a definite virological and/or biochemical confirmation is required. The possible emergence of such changes in HHV-6 DNA polymerase in patients receiving CDV therapy should be taken into account in the treatment of HHV-6 infections.

A Case of Drug-induced Hypersensitivity Syndrome

Drug-induced hypersensitivity syndrome (DIHS) is a rare but severe disease associated with multiorgan failure. The association of DIHS with human herpes virus 6 (HHV-6) has recently been reported. We report on an 89-year-old woman with allopurinol-induced DIHS diagnosed on the basis of symptoms and laboratory examinations. A rash appeared as erythema on the trunk and extremities and edematous erythema on the face. Renal dysfunction, leukocytosis, eosinophilia, and atypical lymphocytes were also present. An elevated titer of antibodies against HHV-6 and HHV-6 DNA in the blood were observed during the course of the disease (1 : 20 to 1 : 1280). Discontinuation of allopurinol administration and systemic corticosteroid treatment led to an improvement, but symptoms worsened when the corticosteroid dosage was tapered. An elevated titer of antibodies against cytomegalovirus was detected during the course of the disease. The patient died of pneumonia, most likely related to cytomegalovirus. This case indicates that, in addition to the reactivation of HHV-6, reactivation of cytomegalovirus may modify clinical disease activity.

Incidence of human herpes virus-6 and human cytomegalovirus infections in donated bone marrow and umbilical cord blood hematopoietic stem cells

This study examined the incidence of human herpes virus-6 (HHV-6) and human cytomegalovirus (HCMV) infections that are potentially transmitted to haematopoietic stem cells (HSC) transplant recipients via bone marrow (BM) or umbilical cord blood (UCB). Bone marrow progenitor cells were collected from 30 allogenic BM donors. UCB HSC were collected from 34 subjects. The extracted DNA was then processed using nested polymerase chain reaction (nPCR) technique. HCMV and HHV-6 serological status were determined by enzyme immunoassay (EIA). Nested PCR identified HCMV in 22 (73%) of 30 samples of BM progenitor cells but in only eight (23.5%) of 34 samples of UBC HSC ( P = 0.001). HHV-6 DNA was detected in 11 (36.6%) of 30 BM progenitor cells and in only one (2.9%) of 34 UBC cells ( P = 0.002). Both HHV-6 and HCMV infections were determined in nine (26.5%) of 34 bone marrow samples. The results indicate that, the risk of HCMV and HHV-6 via BM progenitor cells is higher than transmission by UCB cells ( P= 0.04).

Human herpesvirus-6 DNAemia in immunosuppressed adult patients with leukemia at risk for mold infection

Little is known about human herpesvirus-6 (HHV-6) in leukemia patients. We prospectively followed 37 leukemia patients at risk for mold infection. HHV-6 DNA was detected from whole blood specimens in 11 patients (30%). History of granulocyte transfusions (p=0.05) and prior relapse of leukemia (p=0.07) were the only independent predictors of HHV-6 DNAemia.

Detection of HHV-8 and HPV in laryngeal carcinoma

Objective In this study we aimed to investigate the presence of human herpesvirus 8 (HHV-8) and human papillomavirus (HPV) in laryngeal carcinoma. Materials and methods Fifty patients operated on because of laryngeal carcinoma were included in the study. Forty-seven had squamous cell carcinoma (SCC) whereas three had verrucous carcinoma. Fresh tumoral tissues, or tumoral tissues obtained from archival paraffin-embedded blocks, were examined. HHV-8 DNA and HPV DNA were detected using polymerase chain reaction (PCR) and viral genotypes of HPV were determined via the hybrid capture method. The presence of HHV-8 DNA and HPV DNA were also investigated in normal appearing laryngeal tissue collected from 50 cadavers at autopsy. Results HPV DNA was detected in seven patients (7/50; 14%) (5 out of 47 patients with SCC (5/47; 10.6%) and two out of three patients with verrucous carcinoma). HHV-8 DNA was detected in five patients and they all had SCC (5/47; 10.6%). One case had both HHV-8 and HPV DNA. None of the control samples from cadavers harbored HHV-8 DNA, or HPV DNA. There was a statistically significant correlation between HHV-8 DNA and HPV DNA positivity and laryngeal SCC (Fisher exact test; p = 0.023 for each). No statistically significant correlations were found between the presence of HHV-8 and/or HPV and age, gender, tumor stage, differentiation, the site of the tumor, smoking and alcohol use. Conclusions The findings of the present study suggest that beside HPV, HHV-8 might have a role in laryngeal carcinogenesis. Further investigations are necessary to clarify the exact role of these viruses in laryngeal carcinoma.

CNS Complications of Primary Human Herpesvirus-6 Infection

Central nervous system manifestations of primary human herpesvirus-6 (HHV-6) are described in 9 children, ages 3 to 24 months, with HHV-6 DNA in the cerebrospinal fluid, in a prospective study at the University of Helsinki, and other centers in Finland.

Human herpesvirus 8 presence and viral load are associated with the progression of AIDS-associated Kaposi's sarcoma

We present the largest longitudinal study to date that examines the association between Kaposi's Sarcoma (KS) disease progression and the presence and viral load of human herpesvirus 8 (HHV-8). Ninety-six men were enrolled at HIV clinics in Atlanta, Georgia, who had KS (n = 47) or were without KS but seropositive for HHV-8. Visits occurred at 6-month intervals for 2 years at which the patient's KS status was evaluated and oral fluid and blood were collected for quantification of HHV-8 DNA and antibodies. The presence of HHV-8 DNA in blood was more common (P < 0.001) and the viral load higher (P < 0.001) in men with KS in comparison with men without KS. Mean HHV-8 viral loads in blood and oral fluids were associated with disease status, being highest among patients with progressing KS, intermediate among patients with stable KS, and lowest among patients with regressing KS. Consistent with our previous report high antibody titers to HHV-8 orf 65 were inversely associated with HHV-8 shedding in oral fluid. We observed a significant association between changes in KS disease severity and the presence and viral load of HHV-8. HHV-8 viral load in blood may provide useful information to clinicians for assessment of the risk of further disease progression in patients with KS.

Rapid detection of human herpesvirus 8 DNA using loop-mediated isothermal amplification

The reliability of a loop-mediated isothermal amplification (LAMP) method for the detection of human herpesvirus 8 (HHV-8) DNA was evaluated. Although LAMP products were produced with the DNA sample extracted from BCP-1 cells, LAMP products were not produced with the DNAs from seven other human herpesviruses. The detection limit of the HHV-8 LAMP method was 100 copies of target sequence/tube. To determine whether the HHV-8 LAMP method could be used to quantify viral DNA, threshold times, which are defined as the time (in s) it takes to reach the threshold turbidity level (0.1), were measured for the amplification of serial dilutions of a DNA plasmid containing the target sequence. The standard curve possessed a correlation coefficient of 0.9428 with a slope of −84.079 and y-intercept value of 1936.2. Additionally, an attempt was made to detect viral DNA in 17 specimens collected from Kaposi's sarcomas and two cell lines obtained from primary effusion lymphomas. HHV-8 DNA was detected in 14 of the 17 Kaposi's sarcoma tissue samples and both of the primary effusion lymphoma cell lines. Viral DNA was not detected in HHV-8 LAMP-negative samples using the real-time PCR method.

Association of Human Herpesvirus-6B with Mesial Temporal Lobe Epilepsy

BackgroundHuman herpesvirus-6 (HHV-6) is a β-herpesvirus with 90% seroprevalence that infects and establishes latency in the central nervous system. Two HHV-6 variants are known: HHV-6A and HHV-6B. Active infection or reactivation of HHV-6 in the brain is associated with neurological disorders, including epilepsy, encephalitis, and multiple sclerosis. In a preliminary study, we found HHV-6B DNA in resected brain tissue from patients with mesial temporal lobe epilepsy (MTLE) and have localized viral antigen to glial fibrillary acidic protein (GFAP)–positive glia in the same brain sections. We sought, first, to determine the extent of HHV-6 infection in brain material resected from MTLE and non-MTLE patients; and second, to establish in vitro primary astrocyte cultures from freshly resected brain material and determine expression of glutamate transporters.Methods and FindingsHHV-6B infection in astrocytes and brain specimens was investigated in resected brain material from MTLE and non-MTLE patients using PCR and immunofluorescence. HHV-6B viral DNA was detected by TaqMan PCR in brain resections from 11 of 16 (69%) additional patients with MTLE and from zero of seven (0%) additional patients without MTLE. All brain regions that tested positive by HHV-6B variant-specific TaqMan PCR were positive for viral DNA by nested PCR. Primary astrocytes were isolated and cultured from seven epilepsy brain resections and astrocyte purity was defined by GFAP reactivity. HHV-6 gp116/54/64 antigen was detected in primary cultured GFAP-positive astrocytes from resected tissue that was HHV-6 DNA positive—the first demonstration of an ex vivo HHV-6–infected astrocyte culture isolated from HHV-6–positive brain material. Previous work has shown that MTLE is related to glutamate transporter dysfunction. We infected astrocyte cultures in vitro with HHV-6 and found a marked decrease in glutamate transporter EAAT-2 expression.ConclusionsOverall, we have now detected HHV-6B in 15 of 24 patients with mesial temporal sclerosis/MTLE, in contrast to zero of 14 with other syndromes. Our results suggest a potential etiology and pathogenic mechanism for MTLE.