MONDAY, July 2 (HealthDay News) -- An international team of researchers has identified the first human antibodies capable of neutralizing different strains of the virus responsible for severe acute respiratory syndrome (SARS).
The SARS coronavirus (SARS-CoV) caused a worldwide epidemic in late 2002/early 2003, infecting 8,000 people and killing about 10 percent of them. A second outbreak occurred in the winter of 2003/2004, but only four individuals were infected.
This new discovery marks a major step towards developing specific drugs and vaccines should the deadly disease re-emerge, experts noted.
"One thing it means is, there's an actual promise of an effective therapeutic [approach] for SARS, which we currently don't have," said Dr. Brian Currie, medical director for research at Montefiore Medical Center in New York City. He was not involved in the study.
The research, conducted by scientists in the United States, Switzerland and Australia, appears in this week's early online edition of the Proceedings of the National Academy of Sciences.
In both SARS outbreaks, the virus' spread was apparently sparked by animal-to-human transmission, meaning future outbreaks are still possible.
The particular viral strain that caused the 2002 outbreak probably no longer exists in nature, the experts said, making it imperative that any vaccine or drug be effective against a variety of animal strains, not just against strains found in humans.
The authors of the study say they have identified two human antibodies that bind to a specific region of the SARS virus.
One of the antibodies, called S230.15, was discovered in the blood of a patient who recovered from SARS, while the other, m396, was taken from a library of human antibodies culled from the blood of 10 healthy volunteers.
The antibodies were tested in a mouse model and in lab tests. In both cases, they were found to neutralize samples of the virus left over from both outbreaks.
They also neutralized samples of the virus taken from wild civets (a cat-like mammal thought to have originally transmitted the virus to humans), although less effectively.
More tests suggested that m396 could neutralize all known forms of the SARS virus.
"These are human monoclonal antibodies that are directed against a protein on the surface of a virus that's actually the binding protein to the virus, so they can prevent, as well as ameliorate, infection," Currie explained.
"The problem in the past is there have been candidate monoclonal antibodies, but they didn't react with each one of the strains for each one of the SARS outbreaks," he continued. "You did not have a reliable candidate for treatment, so this is a big breakthrough. It will allow people to move ahead and actually make this into a treatment modality."
Another expert offered his take on the discovery.
"If there's never another outbreak of SARS, it's of no importance whatsoever," said Dr. Julian Leibowitz, a professor of microbial and molecular pathogenesis at Texas A&M Health Science Center College of Medicine, in College Station.
However, he added, the finding could be crucial in the event the virus re-emerges, since "this provides two antibodies that could be used clinically."
There's more on SARS at the World Health Organization.
SOURCES: Brian Currie, M.D., vice president/medical director, research, Montefiore Medical Center, New York City; Julian Leibowitz, M.D., Ph.D., professor, microbial and molecular pathogenesis, Texas A&M Health Science Center College of Medicine, College Station; July 2-5, 2007, Proceedings of the National Academy of Sciences