Late HHV-6B reactivation after 60 days was an independent risk factor for mortality in Japanese pediatric hematopoietic cell transplant recipients. Older children and those with hematologic malignancy were 10x more likely to develop late reactivation.
Does HHV-6B reactivation impair thymic function leading to delayed immune reconstitution?
HHV-6B directly infects thymocytes, presumably affecting thymopoeisis. A review in Bone Marrow Transplantation explores the intriguing relationship between HHV-6B, T-cell reconstitution and aGVHD after allogenic hematopoietic cell transplantation.
HHV-6 and lymphoproliferative syndromes: a review
The authors discuss how HHV-6 may contribute to the progression of reactive lymphoproliferative disorders by spurring a dysfunctional immune response.
HHV-6 viremia impairs late T-cell reconstitution in HCT
Dutch investigators found that hematopoietic cell transplant patients with high levels of HHV-6 viremia have reduced late immune reconstitution while early reconstitution was not affected.
Large scale sequencing effort of HHV-6B defines global diversity, finds new genes, and identifies changes due to viral culture
A gigantic sequencing effort by investigators at University of Washington has provided a wealth of new information about the HHV-6B genome, including important flaws of the reference strains currently in use.
High rate of HHV-6 end-organ disease and mortality in pediatric transplant patients
Stanford investigators found that high levels of HHV-6 viremia following allogeneic stem cell transplants were associated end organ disease and greater non-relapse mortality.
Foscarnet prophylaxis reduces severity but does not prevent HHV-6 encephalitis
A Japanese trial of foscarnet prophylaxis in cord blood transplant patients was successful in reducing severity and mortality as well as suppressing high viral loads, but it failed to prevent encephalitis. The authors note that the blood brain barrier must be inflamed to allow effective penetration of the drug into the central nervous system and speculate that the prophylaxis may have protected the meninges.
HHV-6A sequences found in ovarian cancer tissues but not in controls
A broadscale investigation of the ovarian cancer oncobiome using a microarray system PathoChip found HHV-6A sequences at or near genes associated with tumorigenesis in ovarian cancer tissue samples.
Dense infection of the hippocampus in primary HHV-6B encephalitis
The autopsy of an infant with HHV-6B encephalitis showed a 4-5 fold increase in the viral load of the hippocampus compared to other parts of the brain. Neurons, oligodendrocytes and vascular endothelial cells were infected, but not astrocytes or microglia.
HHV-6 infection of NK cells causes dramatic changes in miRNA and transcription factors that govern immune function
Italian investigators showed that HHV-6A and -6B infection of natural killer cells have a remarkable effect on the expression of miRNAs and transcription factors, which in turn control natural killer cell development, maturation and function.
Deep sequencing analysis finds HHV-6, CMV and EBV in a subset of stomach and colon cancers
A team at University of Pittsburgh analyzed a large database of deep sequencing data from tumor and control tissues to look for viral sequences in 22 different cancers. They were surprised to find several herpesviruses in gastrointestinal cancers but not in control tissues.
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HHV-6 acute liver failure in an immunocompetent child: case report
HHV-6 is rarely identified as the cause of liver dysfunction in immunocompetent children, in part because HHV-6 is not included in routine testing, and HHV-6 infections can be highly localized to the liver. In this case, an alert team in Arizona identified HHV-6 by needle biopsy.
HHV-6 myelitis after cord blood transplantation
Japanese investigators described HHV-6 myelitis in patients who had received cord blood transplantations and report that where HHV-6 reactivation is suspected, early antiviral intervention can dramatically improve patient outcomes.
HHV-6B reactivates first, proceeds to end organ disease faster in transplant patients
Investigators at Fred Hutch Cancer Research Center found that HHV-6B is the first DNA virus to reactivate at a median of 3 weeks, compared to CMV, EBV and Adenovirus at 5-6 weeks. HHV-6B also peaked rapidly, unlike other DNA viruses that took 3-6 weeks to reach peak viral load. HHV-6B reactivation resulted in increased mortality after 100 days.