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Meta-analysis finds at least 8% of umbilical cord blood transplant patients develop HHV-6 encephalitis; calls for routine HHV-6 surveillance in all cases of UCBT

A group of international investigators have collaborated on a meta-analysis to determine the significance of HHV-6 encephalitis in cord blood transplant patients, which has been published this week in Bone Marrow Transplantation.  Reviewing the published literature on HHV-6 and stem cell transplantation (SCT), the group found that patients receiving umbilical cord blood as the stem cell source (UCBT) experienced elevated prevalences of both HHV-6 reactivation (72%) and HHV-6 encephalitis (8%) when compared to patients receiving traditional (non-UCB) hematopoietic stem cell transplantation (HSCT) (37% and 0.5%, respectively).  This finding is consistent with results from a large cohort study published earlier this year by Harvard, which reported that HHV-6 encephalitis might also be associated with a fatality rate of up to 50% among UCBT patients (Hill 2012)...  Read More

Epilepsy following HHV-6 Limbic Encephalitis in Pediatric Transplant Patients

A group from the Royal Children’s Hospital in Melbourne, Australia has reported the development of epilepsy after HHV-6 posttransplant limbic encephalitis (PALE) among children receiving stem cell transplantation with cord blood (CBT).  The group questions whether preemptive treatment is sufficient to prevent the high rate of death, epilepsy and permanent neurological deficits associated withHHV-6 PALE, and suggests that HHV-6 antiviral prophylaxis must be considered in all CBT patients.

Of 84 children who underwent CBT at their institution, 6 (7%) developed HHV-6 PALE, and three of these six developed symptomatic generalized epilepsy (SGE) after a silent period of 11-18 months.  SGE is a condition characterized by progressive, global cognitive impairment with generalized epilepsy, and represents the most severe endpoint of several epileptogenic processes within the brain...  Read More

HHV-6 Latent Infection Identified in Patients with Glioma

Investigators from Nanjing Medical University led by Dr. Kun Yao have found HHV-6 latent infection in glioma tissues, and have isolated a strain of HHV-6A from the glioma cyst, supporting earlier studies that suggest the involvement of HHV-6 in the pathogenesis of adult and pediatric gliomas. 

Using nested PCR and immunohistochemistry (IHC), Dr. Yao’s team identified HHV-6 DNA and protein in tissue from 42.5% of gliomas compared to 7.7% of normal brain tissue. In addition, elevated levels of several cytokines promoted by HHV-6 in astrocyte cultures (including IL-6, IL-8, and TGF-beta) were also observed in HHV-6-positive cyst fluid samples from glioma tissues... Read More

Group identifies HHV-6B-specific CD8+ T Cell response

A new study from the University of Munchen in Munich, Germany, has identified a subset of CD8+ T cells that specifically recognize HHV-6B and not HHV-6A.  The group is led by Dr. Andreas Moosman, who presented preliminary findings at the 7th International Conference on HHV-6 & 7 in 2011.  Their work demonstrates that a specific class of CD8+ T cells recognizes HLA-A2-restricted peptides from the viral structural proteins U54 and U11, and displays several antigen-specific antiviral effector functions.  HHV-6B-infected primary CD4+ T cells are recognized by these CD8+ T cells in an HLA-restricted manner, and furthermore produce antiviral cytokines, which contribute to the effective killing of infected cells.  HHV-6A infected cells, on the other hand, are not recognized by the CD8+ T cells... Read More