Science News

E. coli vaccine?

Sat, 8th May 2010

Scientists have identified a number of fruitful vaccine targets capable of protecting against E. coli infections.

E. coli are common bacteria found loitering harmlessly in the insides of all of us as so-called commensal flora.  But some strains of the bug, like the potentially deadly E. coli O157, are much more malign and capable of causing significant disease including gastroenteritis and kidney failure.  Other pathogenic strains cause urine infections and some forms of meningitis.

Ideally doctors would like to prevent these virulent strains with a vaccine, but ideally without hitting their harmless commensal cousins, which actually help to protect us from disease by stopping other disease-causing bugs from gaining a toe-hold inside us.

Now an international team of researchers think they have found a way to do it.  Writing in PNAS, Novartis Italy scientist Danilo Gomes Moriel and his colleagues compared the DNA sequences of a meningitis-provoking E. coli strain with a series of harmless strains of the bug, reasoning that the genetic differences must account for the pathogenicity.  They found nineteen pathogenicity islands - genetic regions known to convey virulence - which were missing from the DNA of the commensal strains.

Then, by picking out genes that were linked to markers expressed on the surfaces of the bacteria, and which were absent from harmless strains, they identified over 230 "antigens" made by pathogenic strains but not by friendly forms of the bugs.

Nine of these turned out to be capable of working as vaccines to protect mice against lethal doses of the pathogens, but without affecting their ability to carry the harmless bugs. This suggests an anti-pathogenic E. coli vaccine could be around the corner...

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