H pylori Adherence Linked to Blood Group Antigens

Researchers developing a vaccine for the bacterium Helicobacter pylori, the primary cause of ulcers and a contributor to stomach cancers, have found that the organism has evolved a mechanism to enhance attachment to stomach tissues that depends on preferential binding to the most common blood group antigens in the host population.

Investigators at Washington University School of Medicine (St. Louis, MO, USA) were part of a multinational team seeking to develop a vaccine to prevent H pylori infection. In the current study, published in the July 23, 2004, issue of Science, they focused on differences in the attachment properties of North American strains of H pylori as compared to strains isolated from Amerindian groups in Latin America.


They found that more than 95% of strains that bind fucosylated blood group antigen bound A, B, and O antigens (generalists), whereas 60% of adherent South American Amerindian strains bound blood group O antigens (specialists). This specialization coincided with the unique predominance of blood group O in these Amerindians. Strains differed about 1500-fold in binding affinities, and diversifying selection was evident in babA sequences. BabA is one of several adhesions that modulate H pylori adherence to the stomach wall. BabA binds to the Lewis b antigen receptor.

"Most human populations have a mixture of people with blood types A, B, and O. When the bacteria spread from one person to another, they can not predict the next host's blood type, so they maintain a form of babA flexible enough to bind to all the different Lewis b receptors,” explained Dr. Douglas E. Berg, professor of genetics and of medicine at Washington University. "In Amerindian populations in Latin America, though, almost everyone has blood type O. If we can improve our understanding of how H pylori adheres to the stomach lining, we may be able to develop better ways to prevent or decrease infections. H pylori is a very clever pathogen, but its need to stick to the stomach lining may be its Achilles' heel.”




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