March 7 (HealthDay News) -- A stabilized form of a protein found on streptococcus bacteria may provide protection against strep infections, a new study suggests.

A team led by University of California, San Diego (UCSD), researchers developed the first detailed description of the structure of the streptococcal M protein, which plays a critical role in the virulence of Group A Streptococcus (GAS), which causes a number of diseases, including strep throat, rheumatic fever and necrotizing fasciitis ("flesh-eating" disease).

The researchers conducted tests using M1 protein, the version of the M protein present on the most common disease-associated GAS strains. They also produced a variant of M1 that stimulates the immune system in mice, without causing any of the negative health effects of the natural M1 protein.

These investigations, described in the March 7 issue of Science, may help scientists develop M1 protein-based vaccines against GAS, the researchers said.

"Using X-ray crystallography, we determined that M1 protein has an irregular, unstable structure. 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 as a vaccine," Partho Ghosh, a professor of chemistry and biochemistry in UCSD's Division of Physical Sciences, said in a prepared statement.

"Certain antibodies that are produced by the immune system against M1 protein have been shown to cross-react with normal human tissues, including heart muscle, potentially triggering the serious autoimmune disease known as rheumatic fever," said Victor Nizet, a professor of pediatrics and pharmacy at the UCSD School of Medicine and the Skaggs School of Pharmacy and Pharmaceutical Sciences.

"M1 protein can also act as a toxin, producing clotting abnormalities and lung injury when injected into mice. Therefore, our results with modified M1 provide very novel insight about the role of M proteins in invasive GAS disease and rheumatic heart disease," Nizet said in a prepared statement.

Each year, strep infections afflict more than 600 million people worldwide and kill 400,000, according to background information in a news release about the research.

SOURCE: University of California, San Diego, news release, March 6, 2008