Herpes Simplex May Play a Role in Some Alzheimer's Cases


SALZBURG, AUSTRIA – Herpes simplex virus-type 1 may be the root cause of some cases of Alzheimer's disease, according to research presented at an international conference on Alzheimer's and Parkinson's diseases.

Dr. Matthew Wozniak and Dr. Ruth Itzhaki of the University of Manchester (England) found that human neural cells infected with HSV-1 had contained far more amyloid β than had uninfected cells. “We've examined both neuronal and glial cells, and the increase occurs in both cell types,” said Dr Wozniak.

HSV-1 causes several diseases, including cold sores and herpes simplex encephalitis. Most humans are infected, usually in infancy, and in some the virus is woken from its dormant phase in times of stress.

Previously, researchers from Dr. Itzhaki's laboratory demonstrated that HSV-1 DNA is present in brain tissue and that antibodies to the virus can be found in the cerebral spinal fluid in a high proportion of patients with Alzheimer's disease (AD) and elderly patients who do not show signs of the disease (J. Med. Virol. 2005;75:300–6). The study included 27 AD patients and 13 age-matched controls. Importantly, these same markers are generally absent in the brains of younger people.

Subsequently, the researchers increased the study population to 61 AD patients and 48 age-matched controls (Lancet 1997;349:241–4). They found that HSV-1 DNA in the brain and possession of an apolipoprotein E-α4 allele is a strong risk factor for AD (odds ratio 12).

More recently, the researchers demonstrated that HSV-1 infection decreases the concentration of full length amyloid precursor protein, Dr. Wozniak explained.

“A role for HSV-1 in AD points to the use of antiviral agents as a treatment for the symptoms of the disease,” he suggested.

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