Meningitis bacteria mimic human cells to trick immune system

February 20th, 2009 - 6:56 pm ICT by IANS  

London, Feb 20 (IANS) Reserchers have stumbled upon the deviousness of bacteria that causes meningitis in mimicking human cells to evade the body’s immune system.
The study could open the way to the development of new vaccines that give better protection against meningitis B, the strain which accounts for the vast majority of cases of the disease in Britain.

Meningitis involves an inflammation of the membranes covering the brain and the spinal cord as a result of the infection. The infection can be due to a virus or bacteria, but bacterial meningitis is much more serious with approximately five percent of cases resulting in death.

The disease mainly affects infants and young children, but is also often found in teenagers and young adults. Bacterium Neisseria meningitidis is the most common cause of bacterial meningitis.

Oxford University and Imperial College research team looked at how one protein in the outside coat of Neisseria meningitidis enables the bacteria to avoid being attacked and killed by the complement system, part of the body’s innate immune system.

The complement system is designed to attack all foreign bodies that come into contact with the blood. We have particular sugar molecules on the surface of our own cells that flag them as being part of our body and save them from being attacked and killed.

This system works through factor H, a molecule that circulates in the blood and binds to the sugars on the surface of our cells, preventing any immune response.

Critically, the protein on the outside of Neisseria bacteria also binds factor H. Called factor H binding protein, it makes the bacteria appear like human cells and so prevents any attack from the innate immune system.

Researchers, led by Susan M. Lea of the Sir William Dunn School of Pathology at Oxford and Christoph M. Tang of the Centre for Molecular Microbiology Imperial College, determined the structure of human factor H attached to factor H binding protein on the meningitis bacterium.

They found that the protein in the bacterial coat mimicked the sugars on the surface of human cells precisely, enabling the bacteria to bind factor H in the same way as human cells.

“It’s like the bacteria have stolen someone’s coat and put it on in an effort to look like them,” said Lea, who led the work.

These findings were published in Nature.

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