Genetic differences make some people susceptible to developing meningococcal meningitis and septicaemia, and others naturally immune, a new study has revealed.
The research, led by Imperial College London and the Genome Institute of Singapore, is the largest ever-genetic study of meningitis and septicaemia caused by meningococcal bacteria.
It suggests that people who develop these diseases have innate differences in their natural defences that leave them unable to attack meningococcal bacteria successfully.
The study compared the genetic makeup of 1,500 people who developed meningococcal meningitis, from the UK, Holland, Austria and Spain, with over 5,000 healthy controls from the Wellcome Trust Case Control Consortium.
Researchers looked at half a million common genetic variants scattered across each person's genome, and searched for differences between the patients with meningococcal disease and healthy controls.
The results revealed that those who had developed meningococcal meningitis had genetic markers in a number of genes involved in attacking and killing invading bacteria.
Professor Michael Levin of Imperial College (ICL) London said: "Although most of us have carried the meningitis bacteria at some point, only around one in 40,000 people develop meningococcal meningitis.
"Our study set out to understand what causes this small group of people to become very ill whilst others remain immune. Our findings provide the strongest evidence so far that there are genetic factors that lead to people developing meningitis."
The variations uncovered in the study were around the genes for Factor H and Factor H-related proteins. These proteins regulate a part of the body's immune system called the complement system, which recognises and kills invading bacteria.
Normally, Factor H and Factor H-related proteins ensure that the complement system does not cause excessive damage to the body's own cells. However, meningococcal bacteria can hijack the body's Factor H and use it to ensure that the body does not recognise the bacteria as foreign. The bacteria effectively use Factor H as a 'Trojan Horse,' enabling them to evade the body's defences and preventing the immune system from killing them.
The findings were published in Nature Genetics.