Virus infections When flu viruses make people depressed

Why you can get depressive moods through a flu
It has long been known that viral infections such as flu can cause depressive moods. Why this is so, researchers from the University of Freiburg have now found out. Among other things, a protein that controls the virus defense is responsible.

Influenza can cause typical behavior for depression
Influenza not only leads to physical symptoms such as fever, headache, body aches and insomnia, but can also have psychological consequences and trigger behavior typical of depression. So far, it was not clear how immune defense and mental changes are related. But researchers at the Freiburg University Hospital have now found out in mice why virus infections such as influenza can cause depressive moods. According to a press release of the clinic, among other things, the protein CXCL10 is responsible, which actually controls the virus defense.

Viral infections such as flu can not only lead to physical symptoms, but also trigger depressive moods. Researchers have now discovered why this is so. (Image: Laurentiu Iordache / fotolia.com)

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

Protein inhibits nerve cells
The researchers around Prof. Dr. Marco Prinz, Medical Director of the Institute of Neuropathology at the University Medical Center Freiburg, has shown 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 virus defense. The scientists now showed 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 as a function of their use is called neuronal plasticity and is reduced in the hippocampus even in depression. Interesting in this context is also a study that was published last year in the journal "Nature" and was concerned with whether depressions shrink the hippocampus or whether the disorder is present 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 cancers and autoimmune diseases. The experts now found that interferons act on the same newly described signaling pathway. In future studies, they want to investigate the molecular and cellular basics. "However, our data already suggest that blockade of CXCL10 or its receptors may prevent the first disease-related behavioral changes, at least at the beginning of a viral infection or type I interferon therapy," says Prof. Prinz.

Influence of virus infections on behavior
The research team investigated the influence of virus infection and type I interferons on the behavior of animals in established experiments, which measure learning processes as well as the mood of the animals. According to the data, animals with virus infection or type I interferons showed significantly reduced learning capacity and were less active than the control group, which is considered to be depression-like behavior. To exclude effects caused by the disease itself, the scientists also gave the rodents artificial virus genetic material as well as individual components of the virus. Both activate the immune system without rendering the animals sick. In both cases the mice showed a depression-like behavior. This can be attributed to the behavioral effect on the newly discovered signal path. (Ad)