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THURSDAY, Dec. 4 (HealthDayNews) -- A vaccine against severe acute respiratory syndrome (SARS) has proven successful in an animal model, scientists from the University of Pittsburgh report.

While cautioning that a human vaccine to protect against SARS is probably still years away from the market, the researchers say the tested vaccine looks promising.

"Many other groups are working on similar approaches, but this is the first [SARS] vaccine study that will be reported in a peer-reviewed journal," says Dr. Andrea Gambotto, assistant professor in the departments of surgery and medicine at the University of Pittsburgh School of Medicine and the project leader.

The research appears in the Dec. 6 issue of The Lancet.

Gambotto's team, working with colleagues from the U.S. Centers for Disease Control and Prevention, immunized six rhesus monkeys and administered a placebo vaccine to two control animals. Second doses were given at 28 days. Six weeks later, the researchers evaluated whether they had gotten an antibody response, which shows protection against the disease. All six animals that got the vaccine had detectable antibody levels but neither control animal did.

The animals that received the vaccine also had detectable levels of T-cells, a kind of white blood cell involved in the immune system response to foreign invaders.

SARS is caused by a coronavirus, called SARS-associated coronavirus, that scientists discovered months after SARS was first reported in Asia in February 2003. Before its containment earlier this year, the SARS epidemic of 2003 sickened about 8,098 people worldwide and killed 774 of them, according to the World Health Organization.

The new SARS vaccine was developed, Gambotto says, by first engineering a common cold coronavirus to express the SARS coronavirus antigens. (Antigens are substances such as toxins or bacteria that, when introduced into the body, stimulate the production of protective antibodies.) Then, when the vaccine is injected, it first infects cells and then stimulates an immune reaction to the SARS antigen. The bottom line is protection against the disease, the researchers say.

"These animals don't get SARS like humans, but they do have an antibody response," Gambotto says. "This antibody response was a very strong response. What we are now doing is following the animals to monitor their long-term response, to see how long the response will last."

The team also plans to study the vaccine in ferrets, which Dutch researchers have found do develop SARS symptoms after infection with SARS coronavirus.

Optimistically speaking, Gambotto says, human trials of the new vaccine might start in as little as six months or a year.

"The results are interesting and it's very encouraging," says Scott Winram, a project officer at the National Institute of Allergy and Infectious Diseases.

"One of the research difficulties, as the authors point out, is [having] a valid disease model of SARS," he says.

Winram notes that many other groups of scientists are also researching a SARS vaccine and are taking other approaches. Which vaccine will eventually prove best? "We'll have to wait and see," he says. "None are yet to clinical trials."

More information

For basic information on SARS, try the U.S. Centers for Disease Control and Prevention or the World Health Organization.

(SOURCES: Andrea Gambotto, M.D., assistant professor, departments of surgery and medicine, division of infectious diseases and the Molecular Medicine Institute, University of Pittsburgh School of Medicine; Scott Winram, Ph.D., product development project officer, National Institute of Allergy and Infectious Diseases, Bethesda, Md.; Dec. 6, 2003, The Lancet)

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