The exact role of these two proteins in Alzheimer’s disease is still being debated, with drugs targeting plaque formation falling short of expectations. The fact that they are a feature of the condition clearly indicates that something has gone wrong.
Herpes simplex virus type 1 (HSV-1) and Alzheimer’s disease may be related. In addition to being present in large quantities in the brains of the elderly, HSV-1 has been linked to an increased risk of Alzheimer’s disease in persons who also carry the gene for the disease.
Varicella-zoster, the chicken pox virus that causes shingles, has a similar ability to the herpes virus to remain dormant in nerve cells for years.
Shingles are painful acute inflammation of the nerve ganglia, with a skin eruption often forming a girdle around the middle of the body. The same virus causes it as chickenpox.
Although shingles seldom occur more than once or twice in a lifetime, the ensuing inflammation may increase the risk of dementia. It was thought to be insufficient to cause Alzheimer’s.
However, there are good reasons to believe the two conditions are linked, as per the paper.
Vaccination against the reemergence of the varicella-zoster virus as shingles, for example, showed in population studies in Taiwan, the United Kingdom, South Korea, and the United States to reduce the risk of dementia.
Other experts caution
Some experts who were not involved in the study cautioned that the experiment does not prove that this interaction causes Alzheimer’s disease because creating brain-like tissue outside the human body is a fairly artificial environment.
They argue that the problem is caused by inflammation, a byproduct of viral infection, rather than the virus itself, and that other virus could be just as involved in the disease.
“These are laboratory findings and do not directly implicate these viruses as the main cause of Alzheimer’s disease, but the results are important and should continue to stimulate research,” said Paresh Malhotra, a neurologist at the Imperial College London.