SARS Vaccine Passes Crucial Test
DNA Vaccine Protects Mice -- But Will It Work in Humans?
March 31, 2004 -- An experimental SARS vaccine works in mice and scientists hope it will also pass the test in humans.
When SARS first emerged as a new and deadly human disease, rapid public health efforts avoided a major worldwide catastrophe. Most experts agree that if SARS comes back, we might not be so lucky a second time. That's why Gary Nabel, MD, PhD, director of the Vaccine Research Center at the National Institutes of Health, has pushed forward SARS vaccine research.
Nabel's team has developed a DNA vaccine that carries a SARS gene. The gene encodes one of the surface molecules on the SARS virus. In a major breakthrough, they now report that three doses of this vaccine fill mice with anti-SARS antibodies. After having SARS virus sprayed into their noses, the vaccinated mice get a million times less virus in their lungs than unvaccinated mice.
"DNA vaccination with the [SARS gene] results in protective immunity," Nabel and colleagues write in the April 1 issue of Nature."
The SARS virus is a coronavirus. There's never been a human coronavirus vaccine. Attempts to vaccinate cats against a deadly feline coronavirus ended up making the disease worse, not better. This didn't happen in mice that got the SARS DNA vaccine. But nobody knows what will happen in people.
Nabel and colleagues say that human tests are needed -- not only to find out if the vaccine is safe, but to find out how well it works. And that's complicated, because DNA vaccines are very new. Only a few experimental DNA vaccines have ever been tested in humans. None has yet been shown to protect against human disease, although most researchers consider this to be simply a matter of time.
"It will be necessary to test potential SARS vaccine candidates for their immunogenicity, safety, and efficacy in humans in the event of future outbreaks," Nabel and colleagues write.
SOURCE: Yang, Z.-Y. Nature, April 1, 2004; vol 428: pp 561-564.