Researchers find link between Alzheimer's and herpes viruses
More and more people are suffering from Alzheimer's these days. Researchers have now found that the presence of herpes viruses in the brain appears to be linked to the development of Alzheimer's.
In their current study, the scientists at the Icahn School of Medicine at Mount Sinai in New York found that herpes viruses seem to favor the development of Alzheimer's disease. The doctors published the results of their study in the English-language journal "Neuron".
Do viruses affect Alzheimer's disease?
Viruses have long been suspected of influencing the development of Alzheimer's. Doctors have now attempted to analyze such a connection more closely. They found that virus strains are more common in the brains of those affected at an early stage of Alzheimer's disease. However, it is still uncertain whether the virus is a trigger or a symptom of the disease, the experts explain.
HHV-6A and HHV-7 were more common in Alzheimer's brains
The researchers found that traces of the HHV-6A and HHV-7 variants, which are remotely associated with cold sores and genital herpes, are more common in the brains of patients with Alzheimer's disease. The presence of these viruses in the brain has been linked to Alzheimer's disease, a finding that challenges conventional theories about dementia.
A new mechanism has been found
In their research, the scientists identified a mechanism by which viruses could cause damage to nerve cells typical of Alzheimer's. The results are based on tests of the brain tissue of a total of almost 1,000 test subjects. The two strains of herpes viruses mentioned above were much more common in the brains of people with early Alzheimer's compared to healthy controls, the study authors said. However, there is disagreement among experts as to whether the viruses are an active trigger of the disease or whether the brains of people who are already on the way to Alzheimer's disease are simply more susceptible to infections.
About a million people in Germany suffer from Alzheimer's
Alzheimer's is the most common form of dementia worldwide. Of course, there are also many people with Alzheimer's in Germany. Experts believe that around a million people in this country suffer from the disease. The early diagnosis of Alzheimer's disease is often problematic because the damage to the brain initially proceeds very slowly. As a result, the disease remains undetected for a long time.
Do herpes viruses affect the activity of different genes in the brain?
The viral genomes were detectable in approximately 30 percent of the brains of Alzheimer's patients. In comparison, viruses were practically undetectable in the brains of the healthy control group, explains study author Professor Sam Gandy from the Icahn School of Medicine at Mount Sinai in New York. The study also indicated that the presence of herpes viruses in the brain could affect or control the activity of various genes that are associated with an increased risk of Alzheimer's.
The scientists weren't actually looking for a link between viruses and dementia. Instead, they hoped to find genes that are unusually active in the brains of people with the earliest stages of Alzheimer's. But when they examined brain tissue more closely and compared people with early Alzheimer's and healthy controls, the most striking differences in gene activity were not found in human genes, but in genes that belong to two strains of herpes virus, HHV6A and HHV7.
Increased virus levels in the brain could trigger an immune response
The experts originally looked for molecular abnormalities in the development of Alzheimer's. To this end, four areas of the brain affected by the disease were examined more closely by humans. The medical team found that the genetic makeup of people with some form of dementia was more likely to contain type 6a and 7 human herpes viruses (HHV). An analysis of further data sets was also able to establish such a connection. At the beginning of the study, the experts did not actually search for viruses at all. But the viruses caught the eye, so to speak, explains study author Ben Readhead from the Mount Sinai School of Medicine in New York. The further investigation then showed that the viruses could influence the brain metabolism. An increased virus concentration in the brain could trigger an immune response that promotes the development or progression of Alzheimer's, the expert adds.
Results have been confirmed several times
The authors explain that the team was initially surprised and skeptical about the results. An attempt was made to interpret the results conservatively and to reproduce the results in three different brain banks. The results were also confirmed when the examination was repeated twice. The doctors could at least recognize that the diseased brains carry these viral genomes.
Herpes genes increase the activity of Alzheimer's genes
The scientists could not prove that viruses actively contribute to the onset of the disease, but they found a plausible mechanism for how this could happen. Some of the herpes genes have been found to increase the activity of several known Alzheimer's genes. Earlier studies suggested that viruses could be linked to Alzheimer's. But the current detailed analysis of human brain tissue continues this research and shows a relationship between the viruses and the activity of genes involved in Alzheimer's as well as the brain changes, molecular signals and symptoms associated with the disease, the experts explain .
Alzheimer's is not contagious
The viruses found are not the same as those that cause the known cold sores. They belong to much more common forms of herpes, which almost everyone carries. These forms of herpes usually don't cause any problems, doctors say. The study also does not suggest that Alzheimer's disease is contagious or how a virus can be transmitted from person to person. In addition, there was no evidence that the risk of developing dementia is increased by the appearance of cold sores. (as)