Further study revealed that the bacteria were binding to sLex antigen, which is rare on healthy cells but present on inflamed cells.
The investigators captured a fragment of the bacterial adhesin protein using a technique called receptor activity-directed affinity tagging, which they developed for the 1998 study. They then determined the amino-acid sequence of this fragment and used that to identify the gene encoding the protein. They called the new bacterial protein sialic-acid binding adhesin (SabA).
Last, the researchers developed a strain of H. pylori that lacked the SabA gene and found that those bacteria were unable to adhere to inflamed stomach lining, thereby confirming SabA was responsible for the observation that triggered the study.
Overall, the study suggests a dynamic and constantly evolving relationship between bacteria and host. Of the millions of H. pylori bacteria that live in an infected person's stomach, the researchers believe some reside for a time close to stomach cells, while others reside a short distance away in the film of mucus that protects stomach cells from the secreted acids in the stomach cavity. The bacterial population thereby achieves a beneficial trade-off: In any given patch of stomach tissue, bacteria sitting close to stomach cells are well nourished but are at higher risk of attack by the prowling immune cells, while bacteria lying farther away are less nourished and grow less rapidly, but also are less susceptible to immune-system attack.
"Our findings stress the importance of studying bacterial-host relationships as they exist during infection," says Born. "We must always correlate findings from the research laborator
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Contact: Darrell E. Ward
wardd@msnotes.wustl.edu
314-286-0122
Washington University School of Medicine
25-Jul-2002