Meningitis bacteria dress up as human cells to evade our immune system

The way in which bacteria that cause bacterial meningitis mimic human cells to evade the body's innate immune system has been revealed by researchers at the University of Oxford and Imperial College London, using the European Synchrotron Radiation Facility (ESRF) to collect X-ray diffraction data for their experiment.

The study, published this week in Nature, could lead 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 the UK. Meningitis involves an inflammation of the membranes covering the brain and the spinal cord as the result of an infection. The infection can be due to a virus or bacteria, but bacterial meningitis is much more serious, with approximately 5% of cases resulting in death.

The bacterium Neisseria meningitidis is the most common cause of bacterial meningitis. The Oxford and Imperial research team, funded by the Wellcome Trust and Medical Research Council, used a combination of methods to look at how one protein in the outside coat of Neisseria meningitidis enables the bacteria to avoid being attacked and killed by part of the body's immune system.

The immune system is designed to attack all foreign bodies that come into contact with the blood. There are sugar molecules on the surface of the cells that flag them as being part of the body and stop 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. It makes the bacteria appear like human cells and so prevents any attack from the innate immune system.

The X-ray data for this experiment were collected at three macromolecular crystallography beamlines at the ESRF (ID14, ID29 and BM14) and at beamline ID3 at Diamond Light Source in the UK.

Reference:

M. Schneider et al., Nature, February 2009, doi:10.1038/nature07769;

Top image: Beamline ID29 where the X-ray results were obtained. All ESRF macromolecular crystallography beamlines have automated sample changers, which are particularly useful for examining tricky structures like the Neisseria protein.