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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.

Yolken says he thought retroviruses might be involved because schizophrenia
seems to depend on environmental as well as genetic factors. 鈥淚nfectious agents
are only acting in the presence of a genetic disposition,鈥� he says.

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鈥攖heir 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
诲颈蝉别补蝉别.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.