A new study suggests that a low-level central nervous system (CNS) infection could play a role in chronic fatigue syndrome (ME/CFS) particularly in relation to cognitive and mood related symptoms.
The study conducted at Jikei University Medical School in Tokyo, Japan, has identified a novel human herpesvirus-6 (HHV-6) protein present in ME/CFS patients which they did not find in healthy controls. They believe it may contribute to cognitive and psychological symptoms often associated with ME/CFS as well as other chronic illnesses.
Common symptoms of ME/CFS which are most likely to have a direct link to the activity of the HHV-6 virus include poor concentration, short-term memory loss, mental exhaustion and depression.
Dr. Kondo, who conducted the study and has spent 20 years trying to identify the latent protein responsible for chronic CNS disease and mood disorders said at a recent conference that the "causes of many chronic diseases are unknown and chronic viral infection is one of the most suspected candidates."
Other researchers speaking at the same conference presented findings which support Dr. Kondo's work. Jose Montoya from Stanford University reported that the antiviral drug Valcyte, shown to be effective against HHV-6, resulted in an improvement in the cognitive functioning of ME/CFS patients, but was less effective at tackling the physical fatigue. According to Dr. Kondo, drugs like Valcyte combat active replication but can't completely control low-level smoldering. "To cure the diseases, we have to reduce the latently infected virus or prevent its reactivation," he explained.
Dr. Kondo identified the protein associated with latent (non-replicating) HHV-6-infected nervous system and immune cells and found that antibodies against it were present in 71% of /MECFS patients with psychological symptoms and none of the healthy controls he tested. Further tests indicated that 53% of depression and 76% of bipolar depression patients possessed the antibody.
Researchers have suspected that central nervous system infections could contribute to psychological and central nervous system disorders, and patients with CFS have a much higher than average rate of depression. This virus spreads cell-to-cell instead of releasing viral particles into the bloodstream. This has hampered efforts to demonstrate that the virus plays a role in CNS disease.
"This virus persists in the brain and other tissues, but not the blood, which is where investigators have looked," says Kristin Loomis, Executive Director of the HHV-6 Foundation. "Indeed, standard serum PCR DNA for direct evidence of the virus are useless," she added. New ultra-sensitive assays are under development, she reports, "but currently the best way to identify patients with smoldering HHV-6 infection is to look for elevated IgG antibody titers."
Dharam Ablashi, the co-discoverer of the HHV-6 virus, and the HHV-6 Foundation's Scientific Director warns that the test won't be available in the near future. "It may take years to get the assay validated and into commercial production, but will be worth the wait. This assay could identify large numbers of patients with CNS dysfunction who could benefit from antiviral treatment. The HHV-6 Foundation is working hard to help scientists like Dr. Kondo develop better assays," says Ablashi.
Source: HHV-6 Foundation
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