Viruses can trigger psychiatric disorders, research suggests Date: August 9, 2018 Source: University of Würzburg Summary: Can viruses trigger psychiatric disorders? A new study suggests yes. Accordingly, special disorders are associated with a high rate of infection of a specific herpesvirus.
Immunofluorescence image from the cerebellar cortex region of bipolar patients that shows proteins of human herpesviruses (red) in Purkinje neurons. Astrocytes are stained green.
Credit: Photo by team Prusty
Purkinje cells are a central part of the human cerebellum, the part of the brain that plays an important role in motor learning, fine motor control of the muscle, equilibrium and posture but also influences emotions, perception, memory and language.
Scientists from the Institute for Virology and Immunobiology of the University of Würzburg and their US colleagues have now made a surprising discovery in these nerve cells. They found a high infection rate of Purkinje neurons with the human herpesvirus HHV-6 for the first time in patients with bipolar disorder and/or severe depression. The study was led by Dr. Bhupesh Prusty, group leader at the Department of Microbiology. The scientists have now published the results of their study in the journal Frontiers in Microbiology.
Virus-related inflammation in the brain
"Inherited factors have long been known to increase the risk of developing several types of psychiatric disorders including bipolar disorder, major depressive disorder and schizophrenia," Bhupesh Prusty explains. But there is also strong evidence that environmental factors, particularly those that lead to neuroinflammation early in life, might play an important etiologic role in the pathogenesis of these disorders as well. Viruses are such an environmental factor.
"Pathogens may disrupt neurodevelopment and cross talk with the immune system at key developmental stages," Prusty explains. Children that are infected at a young age usually recover without any late complications. However, the viruses lie dormant (latent) in various organs and tissues including the central nervous system and the salivary glands and can be reactivated under certain circumstances, even after years.
Increased infection rate in two psychiatric disorders
Prusty and his team suspected the human herpesviruses HHV-6A and HHV-6B to play a key role in the genesis of psychiatric disorders. So they studied two of the largest human brain biopsy cohorts from Stanley Medical Research Institute (USA) and what they found confirmed their assumption: "We were able to find active infection of HHV-6 predominantly within Purkinje cells of human cerebellum in bipolar and major depressive disorder patients," Prusty sums up the central result of their study. The results show for the first time that type HHV-6 viruses are capable of infecting neurons and possibly causing cognitive disturbances leading to mood disorder.
According to the scientists, the study disproves the belief that viruses which lie "dormant" and hidden in organs and tissues never cause any disease. "Studies like ours prove this thinking as wrong," Prusty says and he cites another study which shows that Alzheimer's disease can also be caused by human herpesvirus 6A.
In the next step, the Würzburg researchers want to figure out the molecular mechanisms behind HHV-6A mediated cellular damage to Purkinje neurons.
Story Source:
Materials provided by University of Würzburg. Note: Content may be edited for style and length.
Journal Reference:
Bhupesh K. Prusty, Nitish Gulve, Sheila Govind, Gerhard R. Krueger, Julia Feichtinger, Lee Larcombe, Richard Aspinall, Dharam V. Avlashi, Carla T. Toro. Active HHV-6 infection of cerebellar Purkinje cells in mood disorders. Frontiers in Microbiology, 2018 (accepted); DOI: 10.3389/fmicb.2018.01955
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University of Würzburg. "Viruses can trigger psychiatric disorders, research suggests." ScienceDaily. ScienceDaily, 9 August 2018. <www.sciencedaily.com/releases/2018/08/180809112440.htm>
Herpes virus: 8 types
The herpes family of viruses includes 8 different viruses that affect human beings. The viruses are known by numbers as human herpes virus 1 through 8 (HHV1 - HHV8).
Human herpes virus 1Human herpes virus 1 (HHV1) is also known as herpes simplex virus 1 (HSV1). It is typically the cause of cold sores around the mouth. HHV1 can also lead to infection in the genital area causing genital herpes usually through oral-genital contact, such as during oral sex. HHV1 infections are contagious and are usually spread from skin-to-skin contact with an infected person through small breaks in the skin or mucous membrane. The HHV1 virus is more likely to be spread through things like sharing eating utensils, razors, and towels from a person who has an active lesion.
Human herpes virus 2Human herpes virus 2 (HHV2) is also called herpes simplex virus 2 (HSV2). It typically causes genital herpes, a sexually transmitted infection. However, it can also cause cold sores in the facial area. Like HHV1, the HHV2 infection is contagious and is spread by skin-to-skin contact. The main route of transmission is through sexual contact, as the virus does not survive very long outside the body.
Human herpes virus 3Human herpes virus 3 (HHV3) is also called varicella-zoster virus. HHV3 causes chickenpox. It can also cause a recurrent virus infection of the skin, which is called herpes zoster or shingles. Shingles occurs when dormant varicella-zoster virus from an initial bout of chickenpox becomes reactivated. Like its close relative, HHV1, herpes zoster likes to infect skin cells and nerve cells. This virus may also recur along nerve fibre pathways, causing multiple sores where nerve fibres end on skin cells. Because an entire group of nerve cells is often affected, shingles is generally much more severe than a recurrence of herpes simplex. The lesions generally appear in a band-like or belt-like pattern occurring on one side of the body and are often accompanied by itching, tingling, or even severe pain. Healing usually occurs in 2 to 4 weeks, and scars may remain. Postherpetic neuralgia is a complication of shingles where the pain associated with the infection can persist for months and even years. Most people who experience shingles once do not experience it again.
Human herpes virus 4Human herpes virus 4 (HHV4) is also known as the Epstein-Barr virus. It is the major cause of infectious mononucleosis, or "mono" - the "kissing disease." It is a contagious infection and is transmitted through saliva. Coughing, sneezing, or sharing eating utensils with an infected person can pass the virus from one person to another.
Human herpes virus 5Human herpes virus 5 (HHV5) is the official name of cytomegalovirus (CMV). CMV is also a cause of mononucleosis. In people with healthy immune systems, the virus may not even cause any symptoms. It can be sexually transmitted, can cause problems to newborns, and can cause hepatitis. CMV can be transmitted through sexual contact, breast-feeding, blood transfusions, and organ transplants. CMV infection is one of the most difficult complications of AIDS. It may lead to diarrhea, severe vision problems including blindness, infections of the stomach and intestines, and even death. For a virus that barely causes a problem in most people with healthy immune systems, it can be amazingly nasty in people with damaged immune systems, such as people with AIDS.
Human herpes virus 6Human herpes virus 6 (HHV6) is a recently observed agent found in the blood cells of a few patients with a variety of diseases. It causes roseola (a viral disease causing high fever and a skin rash in small children) and a variety of other illnesses associated with fever in that age group. This infection accounts for many of the cases of convulsions associated with fever in infancy (febrile seizures).
Human herpes virus 7Human herpes virus 7 (HHV7) is even more recently observed and is closely related to HHV6. Like other human herpes viruses, HHV6 and HHV7 are so common that most of humankind has been infected at some point, usually early in life. HHV7 can also cause roseola, but it is not clear what other clinical effects that this virus causes.
Human herpes virus 8Human herpes virus 8 (HHV8) was recently discovered in the tumours called Kaposi's Sarcoma (KS). These tumours are found in people with AIDS and are otherwise very rare. KS forms purplish tumours in the skin and other tissues of some people with AIDS. It is very difficult to treat with medication. HHV8 may also cause other cancers, including certain lymphomas (lymph node cancers) associated with AIDS. The fact that these cancers are caused by a virus may explain why they tend to occur in people with AIDS when their immune systems begin to fail. The discovery also provides new hope that specific treatments for these tumours will be developed that target the virus. |
