Although depleting naïve T cells has been successful in preventing acute graft vs host disease in several studies, investigators from Spain reported an unexpectedly high incidence of HHV-6 encephalitis in a cohort of haploidentical transplant patients.
Many institutions are now using a new multiplex qualitative assay to get rapid diagnosis in encephalitis cases in the clinic. Unfortunately, this system cannot identify cases of inherited chromosomal integration, which creates confusion.
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.
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.
Investigators in Japan studied 145 patients who developed HHV-6 encephalitis. At 100 days after transplantation, the overall survival rate was just 58.3%, compared with 80.5% for patients who did not develop encephalitis. High-dose antiviral therapy was shown to mitigate high mortality rates in these patients.
A young woman on rituximab and two other immunomodulatory agents for the treatment of dermatomyositis developed encephalitis with severe anterograde amnesia. As the use of biologic treatments for refractory autoimmune disease has been increasing, physicians are advised to consider HHV-6 and offer prompt antiviral therapy to limit irreversible morbidity.
Latvian researchers studied autopsy material from the olfactory bulb in patients with HHV-6 encephalopathy vs. controls and reported surprising differences.
A new point-of-care assay from bioMérieux can simultaneously and rapidly detect 14 pathogens typically found in encephalitis. The machine is designed to be at the clinic or in the emergency room and can be operated by unskilled technicians. In a study of 1,560 immunocompetent patient samples, a total of 1.35% were positive for HHV-6, or about twice the expected rate of 0.8% found with the inherited chromosomally integrated HHV-6.
A fifth case of limbic encephalitis associated with GAD antibodies and HHV-6 infection has been reported, this time in an immunocompetent woman with chromosomally integrated HHV-6, epilepsy, and psychosis. The patient’s condition improved (with a drop in GAD antibody titers and stabilization of psychotic symptoms) in response to three weeks of antiviral therapy but relapsed when antiviral therapy was withdrawn.
Autopsy brain samples from 51 controls and 57 patients who died with encephalopathy of unknown origin were tested for HHV-6 & HHV-7 using immunohistochemistry, nested and real time PCR.
A prospective study authored by Joshua Hill and Danielle Zerr determined that higher than average HHV-6B DNA levels increased the odds of developing delirium after cord blood transplantation (CBT) by almost three fold. Patients with DNA loads in the top quartile had a 4.5 fold increase in delirium.
Two new reviews conclude that HHV-6 acute necrotizing encephalopathy is tied to a mutation of the RANBP2 gene.
Tehran University of Medical Sciences reports HHV-6 DNA in cerebrospinal fluid (CSF) samples of 8.8% of 114 infants suspected of encephalitis.
Experts emphasize need for larger studies to determine the impact of ciHHV-6 on patient outcomes
Edaravone shows promise for reducing oxidation and neuronal damage in AESD.
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