How bacteria avoids human immune system: Revealed
Last Updated: Wednesday, March 31, 2010, 12:14
Washington: In a key breakthrough, scientists claim to have found how a major bacterial infection avoids the human immune system -- ironically, a trick which could help fight inflammation.

In its research, an international team, led by the University of Auckland in New Zealand and Aarhus University in Denmark, has revealed exactly how the superbug Staphylococcus aureus evades human body's key immune defences.

Lead scientist Prof John Fraser said the six-year-long research focuses on a small protein from the superbug called SSL7 (Staphylococcal Superantigen-like protein 7).

The scientists have shown how this protein binds to Immunoglobulin A (IgA), a special defence antibody in our gut and lung. The SSL7 protein also binds to complement C5, one of a series of proteins that "complement" the work of antibodies in destroying bacteria.

"We've created a structural model of the complex formed when SSL7 binds to IgA and C5. The model has enabled us to see how SSL7 cleverly uses IgA as a 'scaffold' to capture two molecules of C5.

"By doing this, the reaction that brings complement proteins together to destroy the bacteria's cell wall can't take place. By binding to IgA and C5 at the same time, the SSL7 protein simultaneously blocks several crucial parts of the body's immune defence against bacterial infection," Prof Fraser said.

According to the scientists, by knowing how S aureus works to block immune system, researchers can begin to develop therapeutic drugs that directly target proteins like SSL7.

"Remarkably, SSL7 highlights exactly where to pinpoint drugs designed to prevent the unwanted over-activation of C5 that normally leads to a serious inflammatory disorder," Prof Fraser said.

The findings have been published in the 'Proceedings of the National Academy of Sciences' journal.


First Published: Wednesday, March 31, 2010, 12:14

comments powered by Disqus