Virus infections: When flu viruses make people depressed

Virus infections: When flu viruses make people depressed

Why you can get depressed moods from flu
It has long been known that viral infections such as the flu can trigger depressive moods. Researchers at the University Hospital Freiburg have now found out why. Among other things, a protein that controls the virus defense is responsible.

Flu can trigger typical behavior for depression
Flu not only causes physical symptoms such as fever, headache, body aches and insomnia in patients, but can also have psychological consequences and trigger behavior typical of depression. So far it has not been clarified how immune defense and psychological changes are related. But now researchers at the University Medical Center Freiburg have found the reason why mice infections like influenza flu can trigger depressive moods in mice. According to a press release from the clinic, the protein CXCL10, which actually controls the virus defense, is responsible, among other things.

Findings could help patients in the future
According to the information, the protein inhibits a brain region that is also less active in depression during cognitive processes. According to the scientists, the findings could help patients in the future who suffer from depressive moods after a viral infection or after immunotherapy. The results of the work were published in the specialist magazine "Immunity", which belongs to the Cell group. "We have now been able to identify the mechanisms by which the immune system influences the state of mind," said lead author Dr. Thomas Blank, biologist at the Institute for Neuropathology at the University Medical Center Freiburg.

Protein inhibits nerve cells
The researchers led by Prof. Dr. Marco Prinz, Medical Director of the Institute for Neuropathology at the University Hospital Freiburg, demonstrated that the blood vessel cells in the brain play an important role in mediating between the immune and nervous systems. According to the information, these so-called endothelial and epithelial cells form the protein CXCL10, which was previously known to attract immune cells and thus contribute to the virus defense. The scientists have now shown that the protein also inhibits nerve cells in the hippocampus and thus also the cellular basis of learning. As stated in the communication, this property of individual synapses and nerve cells to change depending on their use is called neuronal plasticity and is reduced in the hippocampus even with depression. Also of interest in this context is a study that was published last year in the specialist magazine “Nature” and dealt with whether depressions reduce the size of the hippocampus or whether the disorder exists before depression.

Symptoms of depression can be caused by immune proteins
According to the Freiburg scientists, symptoms of depression can also be caused by immune proteins, so-called type I interferons. These proteins are used to treat hepatitis C, certain types of cancer and autoimmune diseases. The experts have now found that interferons work via the same, newly described signaling pathway. In future studies, they want to examine the molecular and cellular basis. "However, our data already suggests that at least at the beginning of a virus infection or with type I interferon therapy, a blockade of CXCL10 or its receptors can prevent the first disease-related behavior changes," said Prof. Prinz.

Influence of viral infections on behavior
The research team investigated the influence of virus infection and type I interferons on the behavior of animals in established experiments in which learning processes, but also the mood of the animals are measured. Animals with viral infection or type I interferons were reported to have significantly impaired learning ability and were less active than the control group, which is considered depression-like behavior. In order to rule out effects caused by the disease itself, the scientists also gave the rodents artificial virus genetics and individual components of the virus. Both activate the immune system without making the animals sick. In both cases the mice showed a depression-like behavior. The behavioral effect can thus be traced back to the newly discovered signal path. (ad)

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