ABOUT HHV-6
Human Herpesvirus 6 (HHV-6) is an immunosuppressive and neurotropic virus that can cause encephalitis and seizures during a primary infection or when reactivated from latency in immunosuppressed patients. New research suggests that HHV-6 may play a role in several chronic neurological conditions including MS, mesial temporal lobe epilepsy, status epilepticus and chronic fatigue syndrome. There is an urgent need for more sensitive diagnostic assays and for studies that can prove or disprove the important disease associations that have been suggested. HHV-6 was discovered in 1986 in AIDS patients with cancer and lymphoproliferative disorders...MORE ON HHV-6 HERE
LATEST HHV-6 NEWS:
April 2011
HHV-6 reactivation in stem cell transplant patients associated with cognitive decline and delerium. Danielle Zerr and associates at University of Washington studied cognitive functioning in 315 transplant patients and found that those with HHV-6 detected in the plasma were more likely to develop cognitive problems or delerium by day 84. The virus affected characteristics of cognition such as attention, processing speed and concentration but not visuospatial perception, fine motor speed or coordination. Multivariate analysis indicated that HHV-6 reactivation could predict outcome on measures of cognitive flexibility/ divided attention. Abstract
Mesial temporal lobe epilepsy brain resections found to have HHV-6B DNA and elevated NF-κB expression. Min-Jin Li and colleagues from China have found that 28% of refractory epilepsy patients have high levels of HHV-6B DNA in their brain tissues when they have brain resections as a last resort to halt seizures. This study confirmed several earlier findings, including a 2007 study by NINDS investigators (Fotheringham 2007a). The group used immunohistochemistry, real time PCR and other techniques to demonstrate that the HHV-6 was found in the same cell locations as NF-κB, a key transcription factor associated with inflammatory responses. The subset of patients found with HHV-6-positive DNA had a history of febrile convulsions. Abstract.
HHV-6 DNA found in epilepsy patients with a history of encephalitis. Niehusmann and colleagues from Germany found HHV-6 DNA in 55% of the temporal lobe epilepsy patients with a history of encephalitis, and none of the controls, using nested PCR. Unlike the Li and Fotheringham studies featured above, they did not find HHV-6B in the subset of patients with a history of febrile seizures. The difference may be due in part to the fact that the Li and Fotheringham studies analyzed fresh rather than stored tissues. Abstract
HHV-6 integrates into the chromosome during latency and reactivates in response to chemical stimulation. Peter Medveczky and colleagues determined that HHV-6 uses a novel form of latency. The virus finds safe harbor inside the human chromosomes to evade the immune system. Medveczky made this surprising finding by studying patients who have a rare form of HHV-6. These patients are actually born with HHV-6 integrated into every cell of their body, and the virus is passed from parent to child. Many scientists believed that this integrated virus could not be reactivated, but Medveczky's group determined that chemical stimulation can cause the integrated virus to reactivate and start producing active virus. See Abstract from PNAS.
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