Research presented at the national meeting of American Chemical Society this week could put an end to worldwide blood shortages. 

A team at University of British Columbia have isolated an enzyme from human gut bacteria which can strip antigens from red blood cells, producing the universal donor type O blood. Stephen Withers, who led the team at UBC, revealed that this technique can produce type O blood up to 30 times more efficiently than previous methods.

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To understand how this technique works, it helps to know the science behind the ABO blood grouping system. Each letter stands for a different antigen, a sugar molecule present on the outer surface of red blood cells. Our immune systems recognise antigens and can mount a defensive response if they identify unfamiliar ones such as those found on invading pathogens or non-self blood. This causes problems during transfusions: people with blood type A cant receive type B, and vice versa, without invoking a potentially fatal immune attack. 

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Red blood cells (erythrocytes) and their antigens. 

Image: Australian Academy of Science

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The solution lies with blood of type O. Because it's free from antigens, this universal brand can be given to virtually anyone without triggering an immune response. This is why Withers' technique of producing type O on demand from type A and B stocks holds such promise. He believes it will prove most useful in emergencies, remote communities, or armed conflicts--situations where the universal donor blood is great demand.

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To find this enzyme, the team at UBC searched in bacteria residing in the human gut. “We knew that those same sugars that are on our red blood cells are also produced on the lining of the gut wall,” Withers told NewScientist. By extracting the gene sequences of bacteria in faeces, and then inserting the genes into Escherichia coli, the researchers were able to identify a new family of sugar-stripping enzymes. These enzymes usually enable gut bacteria to harvest sugars from gut wall proteins called mucins, but when combined with type A blood they were shown to remove the antigens, resulting in type O blood.

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In addition to being much faster than previous methods, Withers' process can be applied to whole blood (i.e. blood bags) and should remain cost efficient for large scale applications, although there is one caveat. Type A blood cells can also display a non-sugar antigen, called rhesus D (Rh), so in order to produce truly universal blood, you'd need to start with Type A (Rh-) negative, or develop another technique capable stripping the Rh antigen.

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Withers admits they're still a long way from developing this method for clinical application, but the early results look promising. “We need to ascertain that no adverse changes to the red blood cell take place,” says Withers, describing the first obstacle. Next, the team will have to prove that they can remove all traces of the enzyme before transfusion, to prevent cross-reaction with the recipients own blood, or other cells. They hope to begin trialling the treatment in the clinic soon after these checkpoints have been cleared.

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“I think this is really exciting,” says David Kwan, biologist and previous colleague of Withers. “I might be biased, but I’ve been around this research for several years now, and I think the approach they are using in their lab with these enzymes is improving more and more. It’s showing real promise.”

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Cover image: Unsplash.com