Potential Biological Marker for Schizophrenia Identified
Nov. 19, 1999 (New York) -- Elevated levels of an enzyme associated with a particular viral infection have been found in patients experiencing their first episode of schizophrenia, adding further support to the theory that there is a genetic-viral link in schizophrenia, according to a recent presentation at the Fifth Annual Symposium on the Neurovirology and Neuroimmunology of Schizophrenia and Bipolar Disorder.
The cause of schizophrenia is unknown but a genetic component has long been established. Environmental causes have also been suspected due to associations seen between maternal infections during pregnancy and subsequent development of schizophrenia in the child. However, researchers have not been able to pinpoint a link between the mental disorder and a particular type of virus. This study is the first to identify a potential biological marker to help identify people at risk of developing schizophrenia.
Researchers at the Stanley Neurovirology Laboratory, associated with Johns Hopkins University, are focusing on the role of genetic material from retroviruses that was integrated into the human DNA millions of years ago. Retroviruses are a type of virus that can only live by incorporating part of their genetic material into the host, or human DNA.
Schizophrenia may result from activation of the retroviruses, according to co-author Robert Yolken, MD, director of the Stanley Neurovirology Laboratory. "Why they get activated, we don't know," he tells WebMD. Suggested activators include another virus, such as the flu, or an environmental factor present during life in the womb or infancy.
Retroviruses cannot reproduce by themselves. They exploit living host cells and use the enzyme reverse transcriptase (RT) to replicate. High RT levels, therefore, are presumed to reflect retrovirus activation. In previous research, Frances Yee, PhD, and her co-investigators found that the brain tissue of schizophrenics yielded higher levels of RT activity than people without schizophrenia.
In the current study, Yee, working with collaborators in Germany, compared RT activity levels in the fluid surrounding the brain and spinal cord of 18 hospitalized patients with a recent onset of schizophrenia to 18 people without schizophrenia. RT levels in the schizophrenia group were almost four times that of the other group. RT levels in patients with long-term schizophrenia were much lower than in patients who had been recently diagnosed with the disease. "Finding this activity in [the fluid] could give us the first real tool for identifying patients with schizophrenia," says Yee.
"This data is very provocative. It definitely indicates that there is a connection between retroviruses and the disease [schizophrenia]," Erik Lillehoj, PhD, tells WebMD. Lillehoj is director of research at Roveko Ltd., in Gaithersburg, MD. Lillehoj was not associated with Yee's investigations.
Interest in the association between viral infections and mental illness has grown in recent years. "There was some speculation by people decades ago that infectious agents were linked to serious mental illnesses, such as schizophrenia and bipolar disorder [manic depression]. That theory was not generally accepted. Now, there is evidence coming in from researchers from independent labs ... that there could be an association between viruses and these [mental illnesses]," Darrenn J. Hart, PhD, of Tulane University School of Medicine, tells WebMD in an interview seeking objective commentary. In his work, Hart has found evidence of antibodies against retrovirus in the blood of half of the patients he tested who were diagnosed with schizophrenia and bipolar disorder.