Some cases of schizophrenia may be caused by viruses activating ancient viral DNA lurking in our genome, claim researchers in the US. If so, it might be possible to treat or even prevent the disease with antiviral drugs.
We all carry around retroviral DNA from viruses that inserted themselves into the human genome millions of years ago. These 鈥渆ndogenous鈥� retroviral genes are similar to those of retroviruses such as HIV, but they are usually inactive and don鈥檛 cause problems.
Now David Yolken of Johns Hopkins University in Baltimore and his colleagues have found traces of active endogenous retroviruses in the cerebrospinal fluid of 10 out of 35 patients recently diagnosed with acute schizophrenia. A control group of people without schizophrenia showed no trace of these genes.
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Yolken says he thought retroviruses might be involved because schizophrenia seems to depend on both environmental and genetic factors. 鈥淚nfectious agents are only acting in the presence of a genetic disposition,鈥� he says.
Fever first
Support for the idea comes from anecdotal evidence that patients often suffer a fever immediately before the onset of schizophrenia. People with HIV can also develop schizophrenia-like symptoms that diminish when they are given antiviral drugs. 鈥淲e don鈥檛 know whether it鈥檚 one retrovirus, or more than one,鈥� Yolken says. He speculates that the activated viruses trigger schizophrenia by interfering with a specific gene.
But Yolken admits that the team鈥檚 work doesn鈥檛 show that endogenous retroviruses are to blame 鈥� their activation could be a side effect rather than a cause of the disease.
鈥淚t鈥檚 quite hard to prove,鈥� he says. 鈥淵ou have to show that if you modulate the infection, you can change the course of the disease.鈥�
But there鈥檚 no direct way to interfere with endogenous retroviruses, Yolken says. Instead, the team will soon start tests to see if herpes drugs can reduce the symptoms of patients with recently diagnosed schizophrenia.
While herpes isn鈥檛 a retrovirus, the researchers think it can activate retroviruses. They say there is evidence of past herpes infections in some patients.
More at: Proceedings of the National Academy of Sciences (vol 98, p 4634)