Cultured brain receives Alzheimer’s from herpes virus



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Researchers have seen, among other things, how the cultured mini-brain loses nerve cells when infected with cold sores. The left image shows healthy brain tissue, the right infected.

Photo: Dana M. Cairns / TT

Researchers have seen, among other things, how the cultured mini-brain loses nerve cells when infected with cold sores. The left image shows healthy brain tissue, the right infected.

A new study reinforces the suspicion that the common cold sore virus can reach the brain and cause Alzheimer’s disease.

For several years now, more and more have been pointing out that there is a link between the cold sore virus and Alzheimer’s disease. However, the causal link is unclear. The researchers have referred to population studies and simple cell cultures, or genetically altered animal models. But now, a group of American scientists has investigated how the virus affects a three-dimensional “mini-brain”, which is cultivated by stem cells. In this way, they can see how the virus affects healthy brain tissue, which strengthens suspicions.

– It is a very well done and interesting study. And it’s a complex model with nerve cells and glial cells, so they also get part of the brain’s immune system, says Hugo Lövheim, a researcher at the Geriatric Center at Norrland University Hospital in Umeå.

He is not involved in the new study, but has previously investigated the link between the cold sore virus and Alzheimer’s disease in population studies.

Clear signs of disease

When American researchers infected the mini brains with the herpes simplex virus type 1, which is called the mouth sore virus, they saw several clear signs associated with Alzheimer’s disease. The groups of small cells, among other things, developed beta-amyloid plaque, which is one of the main characteristics, and the signaling decreased among the nerve cells. In addition, around 40 genes that are linked to Alzheimer’s were activated.

“Never have so many signs of disease been detected in a laboratory experiment,” researcher David Kaplan said in a study news release, which is published in Science Advances.

Hugo Lövheim points out that the new study shows how Alzheimer’s can develop in brain tissue that doesn’t have an inherited risk of the disease, unlike many other experiments done on cell cultures with genetic predispositions to Alzheimer’s.

Hidden in the nerve

But how could a virus that causes cold sores affect the brain? This is probably due to the fact that the virus is hidden in the large nerve of the face, the trigeminal nerve, between the outbreaks, and from there it can reach the brain, explains Hugo Lövheim.

– Trigeminus not only irrigates the face, but also the meninges in the lower part of the brain. Therefore, although it has not yet been proven, it is likely that the virus can cross into the brain and establish itself there.

According to the study of the EE. In the USA, an incredibly small amount of virus is enough to overcome the blood-brain barrier that will protect the brain from infection. In the experiments, the researchers found that a dose of infection corresponding to a single virus particle per 10,000 brain cells was sufficient to cause extensive symptoms of Alzheimer’s.

Upset lip

Anyone who gets infected with a cold sore virus gets a chronic infection; The virus is very adept at staying away from the body’s immune system and generally stays there throughout its life. In some people, the infection occasionally flourishes and causes the typical blisters in the mouth and often a tingling sensation on the lips. According to Hugo Lövheim, it may be that the virus will later flourish in the brain, if it has managed to establish itself there.

– Beta-amyloid is probably part of the brain’s defense against infection, which could explain the increase in plaque due to the virus. A single infection probably doesn’t hurt, but the cold sore virus produces a low-grade, long-lasting infection, which is in good agreement with how the disease develops over a long time, says Hugo Lövheim.

TT: Is there anything you can do to protect yourself?

– From middle age, it may be convenient to consider treatment when this type of recurrent cold sores occurs, to suppress the virus and prevent it from reaching the brain. So it must be in pill form, so that you are infected with the viruses found in the nerve, because the ointments only bite the viruses that are present on the lips, says Hugo Lövheim.

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