WASHINGTON - It may be possible to make a safe vaccine against the type of bacteria best known for causing "strep throat" and rheumatic fever, researchers at the University of California, San Diego are reporting today.
The little piece of the bacterium that causes serious disease can be altered slightly into a form that may work as a vaccine, according to a study in the journal Science.
Group A streptococcal infections affect more than 600 million people each year and kill 400,000 globally. Most infections cause strep throat, which is easily treated with antibiotics. But untreated strep throat infections can develop into rheumatic fever, an often deadly inflammation of the heart. In countries where antibiotics are not easily available, rheumatic fever remains common and can permanently weaken the hearts of survivors.
Group A streptococcus, or GAS, also can cause the "flesh-eating" syndrome called necrotizing fasciitis and blood-borne infections, including toxic shock syndrome.
It has been tricky to try to design a vaccine against GAS because the antigen - the piece of the bacterium most easily recognized by the body's immune system - is also the most dangerous part. It causes inflammation and the dangerous overreaction of the immune system that leads to heart damage.
Partho Ghosh and colleagues at UCSD managed to get an image of this tiny structure, called M1 protein, and then created a version of M1 that showed potential as a vaccine in mice.
"Using X-ray crystallography, we determined that M1 protein has an irregular, unstable structure," Ghosh said in a statement. "We created a modified version of M1 with a more stable structure, and found that it is just as effective at eliciting an immune reaction, but safer than the original version of M1, which has serious drawbacks to its use in a vaccine."
Vaccines use antigens to prime the immune system to react against various invaders, by teaching immune cells to look for certain structures or proteins.
