HHV-6 and EBV identified as risk factors in Alzheimer’s Disease
Researchers from the University of Bologna, Italy, have published data suggesting that HHV-6 and EBV are associated with Alzheimer’s Disease (AD) in elderly persons. Previous work has shown that herpes simplex virus type 1 (HSV1) is a risk factor for the development of AD in the brains of people who possess specific genetic factors, and furthermore show that HSV1 can cause specific pathologies that contribute directly to AD disease progression (Lin 2002, Wozniak 2009, Wozniak 2011). Based on these findings, many experts have begun to speculate that other neurotropic herpesviruses could similarly contribute to the pathological mechanisms involved in AD.
In the present study, DNA from peripheral blood leukocytes (PBL) and brain samples were analyzed for the presence of CMV, EBV, or HHV-6. While all tested samples were negative for CMV, EBV positivity was 6% in AD brains, and 45% of PBL samples from AD patients (compared to 31% from controls) were positive for EBV (p = 0.05). HHV-6 was detected in 23% of PBL samples from AD patients and only 4% of controls (p = 0.002). In addition, 17% of AD brains were HHV-6 positive.
The group also followed a population of elderly individuals for 5 years, and found that EBV-positive or HHV-6–positive PBL samples increased significantly among those in the population who developed clinical AD. Further serological analysis revealed increased IgG levels for CMV and EBV antigens in those subjects who developed AD during the follow-up. These detailed findings suggest that EBV and HHV-6 may be environmental risk factors for cognitive deterioration and progression to AD in elderly persons.
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