Type A blood converted to universal-donor blood

Saturday, June 29th, 2019

To up the supply of universal-donor blood, scientists have tried transforming the second most common blood, type A, by removing its “A-defining” antigens:

But they’ve met with limited success, as the known enzymes that can strip the red blood cell of the offending sugars aren’t efficient enough to do the job economically.

After 4 years of trying to improve on those enzymes, a team led by Stephen Withers, a chemical biologist at the University of British Columbia (UBC) in Vancouver, Canada, decided to look for a better one among human gut bacteria. Some of these microbes latch onto the gut wall, where they “eat” the sugar-protein combos called mucins that line it. Mucins’ sugars are similar to the type-defining ones on red blood cells.

So UBC postdoc Peter Rahfeld collected a human stool sample and isolated its DNA, which in theory would include genes that encode the bacterial enzymes that digest mucins. Chopping this DNA up and loading different pieces into copies of the commonly used lab bacterium Escherichia coli, the researchers monitored whether any of the microbes subsequently produced proteins with the ability to remove A-defining sugars.

At first, they didn’t see anything promising. But when they tested two of the resulting enzymes at once — adding them to substances that would glow if the sugars were removed — the sugars came right off. The enzymes also worked their magic in human blood. The enzymes originally come from a gut bacterium called Flavonifractor plautii, Rahfeld, Withers, and their colleagues report today in Nature Microbiology. Tiny amounts added to a unit of type A blood could get rid of the offending sugars, they found. “The findings are very promising in terms of their practical utility,” Narla says. In the United States, type A blood makes up just under one-third of the supply, meaning the availability of “universal” donor blood could almost double.

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