By Sean Henahan, Access Excellence

BERLIN (3/26/95) Do domestic animals transmit a virus to humans that causes psychiatric disorders? An increasing body of research suggests this may indeed be the case.

The suspect virus, Borna disease virus (BDV), was first described a century ago. Named after the region in eastern Germany where it was first described, the virus can cause a fatal encephalitis in horses, cattle and sheep. BDV is a single-stranded RNA virus that established a persistent infection without directly damaging host cells.

Borna disease can also cause neurological symptoms in domestic animals, which is where it gets its nickname, 'crazy virus'. The neurological symptoms resemble those seen in humans with manic depression. (N.B. this is entirely separate from 'madcow disease'.)

It was these neurological symptoms that led researchers to study BDV more closely. Early research indicated that the virus has a tropism for a specific group of neurons in the limbic system, the part of the brain associated with moods and emotions. This in turn led to attempts to isolate the virus from humans with various psychiatric disorders.

About ten years ago, researchers did studies in a population of patients with schizophrenia and other psychiatric disorders and found higher levels of BDV antibodies in the blood of patients compared with controls. In that study, 20% of 70 psychiatric patients showed the presence of BDV antibodies. The highest percentage, 30%, was seen among patients with major depression, while the lowest rate, eight percent, was seen in patients with neurotic depression, a less severe disorder. BDV antibodies have been isolated in about two percent of normal populations.

Next, a German team used fluorescence activated cell sorting analysis of peripheral blood monocyctes to isolate BDV antigen-containing monocytes in patients during acute episodes of disease. Interestingly, these patients had no detectable anti-BDV antibodies.

In their most recent study, the same researchers report isolating BDV genetic material in patients with depression and panic disorders. The patients were drawn from a study group of 139 patients with acute or chronic psychiatric disease. The team isolated peripheral blood monocytes from two patients with chronic psychiatric disease (obsessive-compulsive disorder, organic mood disorder) and four with acute illness (major depression, panic disorder) and then looked for BDV antigen positivity and BDV DNA sequences.

The two chronic patients appeared to express viral activity continuously on repeated testing over a seven month period. The findings in the acute cases were less consistent. In two of the patients, the presence of the viral markers coincided with symptomatic episodes. The two other patients with acute disease did not show viral activity at first, but some weeks later BDV antigen was isolated . As viral activity declined, so too did the patients' symptoms.

"The presence of viral markers seems to coincide with acute disease episodes and to disappear during the patients' recovery or at least during decreases in symptoms. In contrast, a more or less continuous level of viral activity is seen in chronically infected patients," said Dr. Liv Bode, Koch Institute, Berlin, Germany.

The researchers hypothesize that BDV infection may contribute to depressive illness by altering neuronal cells in the limbic system. The leading hypothesis is that BDV, as it inserts itself into neurons, may compromise the function of those cells by binding to neurotransmitter receptors.

"This is the first definite proof of human infection with the animal virus or a related human BDV strain. Although definitive proof of active virus in these patients must await isolation of the virus, the demonstration of BDV DNA is exciting and important evidence supporting the ability of BDV to give rise to human neuropsychiatric disease," said Dr. Bode.

The cause of most of the common psychiatric disorders, including depression, manic depression, anxiety and schizophrenia, remains a mystery. In some cases, symptoms appear suddenly and follows a catastrophic course, while in other cases the disease may be intermittent. Despite a large amount of research, and a lot of familial association evidence, the search for causative genes has produced mixed results. This has helped fuel the search for other factors, such as viral infection.

One group of investigators at the National Institute of Mental Health is pursuing the hypothesis that schizophrenia might be caused by pestiviruses transmitted from household pets to pregnant women or young children. Another group of researchers at the University of Southern California is looking for a link between chronic fatigue syndrome and 'stealth viruses', i.e. viruses that have been incorporated into the host DNA and are no longer recognized by the immune system. These viruses cannot be detected by standard immunological methods or standard culture techniques. However, they can be detected with PCR based techniques, matching DNA sequences with known viral DNA.

Dr. Bode's research appeared in Nature Medicine, V.1, No.3, 3/95.

Science Updates Index

What's News Index

Feedback