US researchers said on Tuesday they had found an antibody that could help prevent infection with the SARS virus.
They found the monoclonal antibody -- a specialized immune system protein -- by looking through a library of existing antibodies.
They said their approach, described in this week's issue of the Proceedings of the National Academy of Sciences, might be used against other newly emerging diseases as well.
"This is really a proof of principle for responding to emerging infectious diseases," Dr. Wayne Marasco of the Dana-Farber Cancer Institute and Harvard Medical School in Boston, said in a statement.
"If the international community works together, it can make a serious dent in the time it takes to develop protective treatments against these threats."
SARS first was seen in November 2002 and between then and June 2003 infected more than 8,000 people globally and killed nearly 800. This year, four people have been diagnosed with SARS in the Chinese mainland.
Severe Acute Respiratory Syndrome is caused by a new virus from the family of coronaviruses that cause the common cold and a range of animal illnesses.
Marasco and colleagues at Dana-Farber, Brigham and Women's Hospital, the US Centers for Disease Control and Prevention, and Children's Hospital Boston tested the antibody in lab dishes of cells and found it blocked the virus from infecting cells.
"It was one of those Eureka experiences," Marasco said. 'It was pretty dramatic."
Antibodies are proteins that either flag or outright destroy invaders such as viruses and bacteria.
Monoclonal antibodies are used to treat disease, including cancer, but have not been developed to protect against disease. It would take years more work to develop this protein as a weapon against SARS, but the researchers said studying its structure may offer a shortcut to developing a drug or vaccine to fight SARS.
Passive immunization -- in which antibodies are infused into a patient's blood -- may also offer a short-term treatment for those sickest with SARS, they said.