H. pylori use the same molecules to fasten themselves securely to the stomach walls, using special "adhesin" proteins that bind with the sugars, researchers report. Thus, the bacteria can co-opt the body's defense system for their own hostile purposes.
"The bacteria are exceedingly adaptive," Born said.
Interestingly, the two adhesins discovered thus far belong to a group of proteins that seem to be unique to H. pylori.
"The bacteria's ancestor seems to have come up with these proteins all by itself," Born said.
This uniqueness bodes well for a vaccine "cocktail" of adhesin proteins, since a common obstacle to vaccines is that they aren't specific enough to be effective, Born explained.
Born and other researchers had previously identified another adhesin protein, called "BabA," on H. pylori's surface, that binds to the sugar molecule "Leb."
To investigate whether the bacteria used other adhesins for similar purposes, the Science authors generated a mutant form of the bacteria lacking the BabA gene. They named the sugar to which it bound, "sdiLex."
Using biopsies from humans and a rhesus monkey, the researchers found that the mutant bacteria were binding to mucus membrane cells of infected individuals, and not those of healthy individuals. The membrane cells seemed to be "shooting themselves in the foot," so to speak, by displaying more sugars once they were under siege by H. pylori.
With the assistance of the sequenced H. pylori genome, the researchers identified the gene encoding the bacterial adhesin protein, which they called "SabA" (for Sialic acid binding Adhesin).
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Contact: Lisa Onaga
lonaga@aaas.org
202-326-7088
American Association for the Advancement of Science
25-Jul-2002