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Gut Microbes Converted Type A Into Universal Donor Blood

Scientists from the University of British Columbia (UBC) have found a way to nearly double the amount of universal donor blood available. They discovered microbes in the human gut that produce two enzymes which efficiently strip type A blood of its antigens, transforming it into type O. This process could ease blood shortages and revolutionize blood donation and transfusion.

Blood shortages are a constant burden to many healthcare organizations. Just in the United States, hospitals use up about 16,500 liters of donated blood for emergency surgeries, scheduled operations, and routine transfusions every day. Occasionally, situation gets critical since patients can’t take just any blood. For a transfusion to be successful, the patient and donor blood types must be compatible. Otherwise, if a person gets the “wrong” type the reaction can be fatal. Now, researchers analyzing bacteria in the human gut have discovered enzymes that can convert the common type A into a universal donor type, O.

“This is a first, and if these data can be replicated, it is certainly a major advance,” Harvey Klein, a blood transfusion expert at the National Institutes of Health’s Clinical Center in Bethesda, Maryland, said for Science.

People can have one of four blood types: A, B, AB, or O. This difference is defined by sugar molecules, or blood antigens, on the surface of the red blood cells. If a person with blood type A receives a type B transfusion, their immune system will notice type B antigens and attack the red blood cells. Type O cells lack these antigens so anyone can receive it. In emergency rooms, doctors often do not have time to determine the patient’s blood type so universal donor blood is irreplaceable in these situations.

Short shelve life of donated blood contributes to the threat of shortage. The collected blood is often stored in a blood bank as separate components. The longest shelf life used for platelets is seven days. Red blood cells, the most frequently used component, have a shelf life of 35-42 days at refrigerated temperatures. Plasma can be stored frozen for up to one year, so at least here situations is a little better. Vrh obrazca

“Around the United States and the rest of the world, there is a constant shortage,” said Mohandas Narla, a red blood cell physiologist at the New York Blood Center in New York City.

Everybody would benefit the most from the increase in the supply of universal blood. Therefore, scientists have tried transforming the second most common blood, type A, by removing its “A-defining” antigens. Enzymes that were used to strip the red blood cell of the respective sugars were not efficient enough to do the job economically.

 A team led by Stephen Withers, a chemical biologist at the University of British Columbia (UBC) in Vancouver, Canada, gave up after years of trying to improve on those enzymes and looked for a better match among human gut bacteria. Some of these microbes “eat” the sugar-protein combos called mucins. Mucins’ sugars are similar to the type-defining ones on red blood cells. In a study published in the journal Nature Microbiology, he presented promising findings.

Peter Rahfeld, UBC postdoc, collected a human stool sample and isolated its DNA with the hope it contains genes, that encode the bacterial enzymes that digest mucins. He chopped this DNA up and loaded different pieces into copies of bacterium Escherichia coli. The researchers hoped to get the microbe produced proteins with the ability to remove A-defining sugars. After they tested two of the resulting enzymes at once, the sugars came right off. The enzymes originally come from a gut bacterium called Flavonifractor plautii.

“The findings are very promising in terms of their practical utility,” said Narla. 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.

For now, researchers will focus their effort on only converting type A since it is more common than type B blood. The team plans to conduct further studies to ensure the process removes all the blood A antigens. Also, scientists need to make sure the microbial enzymes have not accidentally altered anything else on the red blood cells.

Learn more about this game-changing discovery in the video below:

By Andreja Gregoric, MSc

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