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Dr Julian Parkhill
The repeat sequences help the bacterium evade the immune system
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Wednesday, 29 March, 2000, 18:09 GMT
Meningitis bug success
Xavier Nassif
The "A" strain is the most common (Pic: Xavier Nassif)
Scientists have taken a major step forward in their search for more effective treatments for meningitis.

UK and German researchers have succeeded in mapping the entire genetic make-up of the A strain of the bacterium that causes the disease. This is the strain that results in the potentially lethal meningococcal meningitis.

The vast amount of information coming from bacterial pathogen sequencing will underpin almost all future research on these organisms

Dr Julian Parkhill, Sanger Centre
The development comes less than a fortnight after researchers announced they had sequenced the genome of meningitis B.

Meningitis A is the most common form of the bacterium (Neisseria meningitidis) and while it is relatively rare in the UK, this strain is responsible for epidemics in developing countries. In 1997, 500,000 cases of meningococcal meningitis were reported, half of them in Africa.

The work could pave the way for the development of a powerful new vaccine for the disease. At the moment, a vaccine does exist but it offers only limited protection to young children.

Vaccine candidates

The findings of the project, which took over two years and 30 people, at the Wellcome Trust's Sanger Centre in Cambridge, and the Max Planck Institute for Molecular Genetics in Berlin, are published in the journal Nature.

Dr Julian Parkhill, head of the research team at the Sanger Centre, told BBC News Online: "Having the complete genome will allow interested researchers and companies to rapidly find vaccine candidates on a scale not possible before."

There is also a vaccine for meningitis C and work is underway for a jab against strain B. But Dr Mark Achtman, of the Max Planck Institute, warns that a vaccine for meningitis A is still a long way off.

"These bacteria are extremely flexible in adapting to human defences. This will provide difficulties for vaccine development."

It is also hoped the genetic information will help researchers find new methods of detecting and treating infections.

Body's defences

"Bacterial genomics is at the beginning of an exponential curve," said Dr Parkhill. "The more we can find out about diverse pathogens at this fundamental level, the greater will be our understanding of different disease processes.

"The vast amount of information coming from bacterial pathogen sequencing will underpin almost all future research on these organisms."

One of the most interesting findings to come out of the research is that a large part (over 10%) of meningitis A's genome is made up of repeat sequences of DNA which appear to play an important role in helping the bacterium to evade the human immune system.

"We speculate that this repeat DNA is involved in allowing the bacterium to take up DNA from the environment and use it to modify its own surface," Dr Parkhill told the BBC.

"The DNA that Neisseria generally take up is from very closely related strains of Neisseria. So what it would be doing is effectively swapping one of its own genes for a similar but slightly different gene from another Neisseria, which will enable it to have a protein on the surface that has the same function but a slightly different response to the immune system."

The symptoms of bacterial meningitis are a very high temperature, stiff neck, and a blotchy red or purple rash that does not fade when the side of a glass is pressed against it.

The bacterium's genetic map, which has over 2,000 genes
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09 Mar 99 | Medical notes
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