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Cholera sickens 3 million to 5 million people around the world every year, leading to 100,000 to 120,000 deaths, many of them in the Indian subcontinent, where cholera has been endemic for centuries.
People with blood type O often get more severely ill from cholera than people of other blood types. In people with blood type O, scientists found that cholera toxin hyperactivates a key signaling molecule in intestinal cells. High levels of that signaling molecule lead to excretion of electrolytes and water – in other words, diarrhea. Cholera is marked by severe diarrhea that can lead to dehydration, shock and even death.
The researchers confirmed their results in an intestinal cell line originally derived from a person with blood type A. The cell line was modified to produce the type O antigen instead. They found that cholera toxin induced roughly double the amount of the key signaling molecule in cells with type O antigen than in those with type A.
Fleckenstein isn’t sure why cholera toxin induces different responses in cells with different blood group antigens on their surfaces.
“The cholera toxin is known to bind weakly to the ABO antigens, so they may be acting as decoys to draw the toxin away from its true target,” Fleckenstein said. “It may be that the type O antigen just isn’t as good of a decoy as the type A antigen.”