One step closer to the solution of Alzheimer’s disease puzzle – herpes virus, our hidden enemy

Sharing a momentAlzheimer’s disease is the most common condition of the central nervous system responsible for the symptoms of dementia. This defect is clearly associated with age and more often manifests itself in women. The reason of the disease is not fully understood. It is known that the pathogenesis involves accumulation of insoluble protein Aβ in the brain. Recent years brought growing interest in Alzheimer’s disease and scientists have put forward assumptions that the HSV1 virus infection may be associated with this condition. Researchers from Umea University in Sweden have conducted a prospective study in order to prove this relationship.

Approx. 90% of people are infected with Herpes Simplex Virus (HSV1). HSV has a tendency to attack the nervous system and withdraw itself into the ganglia – state of latency. Recurrences of symptoms are peculiar to herpes. They occur during declines in immune resistance.

Hypothetically in old age, when the immune system is weakened, HSV infection can reach the brain (in asymptomatic way). Chronic inflammation leads to changes in the brain cells, which increase the production of protein Aβ. This protein forms the so-called amyloid plaques that cause degeneration of nerve tissue and lead to Alzheimer’s disease.

3432 people of different age and sex took part in this prospective study. Average follow-up duration was 11.3 years. During the period of participation each patient’s blood was tested for the presence of anti-HSV IgG and anti-HSV IgM. The presence of only the first antibody is a proof of the latent state of the virus whereas the presence of the latter is a sign of an active infection. Absence of both antibodies is an evidence of no HSV infection. In order to evaluate dementia, researchers conducted tests which assessed different types of memory, speed of thinking, decision-making and problem solving.

7.6% of patients with IgG antibodies developed Alzheimer’s disease. However, this information turned out to be not important for the study because it has been proven that in patients without any identified anti-HSV antibodies incidence of this disease was similar. In contrast, up to 15% of patients with positive IgM developed symptoms of Alzheimer’s disease.

The final analysis of the results of the study of Swedish researchers has shown that people with active HSV infection have two times greater risk of suffering from Alzheimer’s disease. It turned out that the latent (controlled by the immune system) form a herpes virus has no effect on the incidence of the disease. Large number of participants, long duration and the prospective nature of the study provided high value results. This discovery sheds new light on Alzheimer’s disease and may in the future be used in its prevention.

Written by: Katarzyna Godzisz, Michał Godzisz, Krzysztof Grzechnik

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Would you like to know more? Watch on Alzheimer disease – Histopathology – Brain

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