A comprehensive, large-scale analysis has provided strong evidence of a causal association between HHV-6A and Alzheimer’s Disease. Not only was HHV-6A (and HHV-7) viral load found to be higher, but transcription of HHV-6A genes was also increased among AD patients, and this was observed across multiple brain regions and multiple cohorts. Importantly, host genes affected by HHV-6A were all associated with AD traits and risk genes.
A new meta-analysis published in Blood shows that transplant patients who reactivate with HHV-6 are 2-3 times more likely to develop acute GVHD.
Using a novel serological assay that can differentiate HHV-6A from HHV-6B, investigators found HHV-6A immediate early antibodies to be associated with an increased risk of non-Hodgkin lymphoma.
In 2016, Italian investigators found HHV-6A in the uterus of 43% of women with unexplained infertility but 0% on controls. Now, a second study found localized HHV-6 infection in women with recurrent implantation failure, but not in controls.
German investigators conducted a broad scale analysis of CD8 T cell responses to HHV-6B, identifying novel epitopes with potential for immunotherapy or vaccines. The strongest responses were directed against an epitope from IE-2.
Investigators at the University of Minnesota found that cord blood transplant cancer patients with HHV-6B reactivation in the first 28 days are almost 4x more likely to relapse in the first two years compared to those with no early reactivation.
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.
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.
The authors discuss how HHV-6 may contribute to the progression of reactive lymphoproliferative disorders by spurring a dysfunctional immune response.
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.
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.
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.
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.
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.
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.