The mechanisms leading to HHV-6A/B integration are a subject of intense research by several laboratories. A new paper in PLoS Pathogens provides some understanding as to how HHV-6A/B may integrate host chromosomes.
A Japanese group found that ciHHV6 genes encoding for immunoglobulins were decreased in ciHHV6 individuals, possibly modulating immune responses.
This multiplex qualitative test for cerebrospinal fluid helps physicians diagnose HHV-6 encephalitis quickly, but interpretation must take into account imaging, ciHHV-6 status and other markers.
Transplant patients born with chromosomally integrated HHV-6 have elevated levels of C-reactive protein and tumor necrosis factor receptor 1, both markers associated with increased risk of acute graft-versus-host disease.
A comprehensive study of DNA and RNA-Seq data demonstrated in vivo gene expression in many iciHHV-6 tissues, with strong expression of IE-1 and matching elevated antibody response in iciHHV-6 individuals compared to controls.
A genomic analysis of samples from 141,431 Chinese women found a highly significant association between ciHHV-6 and a variant in the MLCI-MOV10L region. The MLC1 gene is involved in myeloid cell differentiation and the MOV10L1 gene may allow for more efficient integration during spermatogenesis.
Inherited ciHHV-6 has been shown to activate under conditions of immunosuppression and and the pan-HDAC inhibitor TSA activates integrated ciHHV-6 in vitro. This is the first case report of HHV-6 activation in a ciHHV-6 patient who received a pan-HDAC inhibitor drug.
British researchers used molecular dating methods to determine that most strains of iciHHV-6 come from a small number of ancient human ancestors; the youngest found lived over 24,000 years ago. These ancient strains vary considerably from modern non-inherited strains of HHV-6A and appear just as likely to activate as their more modern cousins.
Investigators at Kings College London report that seropositivity for CMV, Herpes simplex 1 and HHV-6 are all associated with a significant shortening of telomeres over a three-year period. Furthermore, the magnitude of the changes was large. For example, CMV seropositivity was associated with the equivalent of almost 12 years of chronological age.
Sequencing of over 8,000 individuals were used to determined the prevalence of 94 different viruses. HHV-7 was the most common virus, with HHV-6B and HHV-6A 4th and 5th respectively.
A team in Japan has reports that ciHHV-6A prevalence is influenced by a “founder effect” and is likely derived from a common ancestor. All of the individuals in the small study were found to have HHV-6A integrated into the telomeric region of chromosome 22, a common site of integration.
A higher prevalence of inherited virus was found in patients
Investigators at Fred Hutchinson Cancer Center determined that transplant patients with inherited ciHHV-6 were twice as likely to develop acute graft vs host disease and three times more likely to develop high level CMV viremia. Transplant patients were also significantly more likely to have inherited ciHHV-6 than donors.
Most herpesviruses maintain latency by forming circular episomes in the nucleus of the cell. Investigators in Germany have provided further evidence that HHV-6A relies on their telomeres, not circular episomes, to maintain a persistent latent infection by integrating into the host chromosome.
A group led by Louis Flamand, PhD in Canada has developed a culture system that can be used to determine how the virus enters latency by integrating into the chromosome, and which drugs cause it to activate.
A new study shows that HHV-6A direct repeats can survive alone in an integrated state without the rest of the viral genome. The study also identified non-telomeric integration of HHV-6A in both in vitro cultured cells as well as one iciHHV-6A patient.