Can our gut bacteria create a universal blood type?

In the UK, approximately 1.5 million red blood cell (RBC) donations are collected each year and used in blood transfusions, despite this impressive number there is still a shortage as demand outstrips supply and most donations are unusable for those in immediate need. The solution could be from an unexpected source – could bacteria found in our gut help blood shortages be a thing of the past?

Donations are hugely important in saving and improving countless lives each year all, but maintaining supplies is incredibly difficult and giving someone the wrong blood type can be life-threatening.

blood-compatibility-chart
Blood compatibility chart, Canadian Blood Services

Donated blood is used in numerous areas, from treating medical conditions like cancer and blood disorders, to surgery, blood loss after childbirth and in research. Many people who have no cure to their illnesses need regular transfusions to remain healthy, like those suffering with Diamond-Blackfan syndrome, a form of anaemia.

Type O- in particular is in high demand due to it being the universal donor, meaning people of any blood type can take a type O- transfusion without their immune system reacting.

As well as the 4 main groups (A, B, AB, and O), the Rhesus system overlays this.ABO System

Each refer to the antigens on the blood surface, these are carbohydrate structures and each group has a different oligosaccharide ending. Those with group A blood have N-acetylgalactosamine at the end of the chain, group B have Galactose, and O lacks these so terminates in fucose. You can also either be Rh+, meaning you have the Rh antigen on the surface, or Rh-, meaning you don’t.

These antigens mean people can accept only certain blood transfusions otherwise it will lead to an immune reaction in which the foreign RBC’s agglutinate (clump) and lysed (destroyed), leading to acute intravascular haemolytic transfusion reaction.

Because of this high risk, O- blood is used in emergency situations when the recipients blood type is not known. This rapidly depletes already low stocks of type O-, so researchers have been looking into ways to bypass the ABO system.

The idea of stripping the RBC’s of their antigens to create type O- blood is not a new proposition, unfortunately previous enzymes have been found to be expensive and inefficient. Now, however, a research team at the University of British Columbia may have found a good candidate.

Steve Withers, professor of glycolysis and ­lead researcher, knew that our gut wall is coated in structures (called mucins) that are made up of the same sugar molecules as the RBC antigens. He hypothesised that there could be bacteria in the human gut that had evolved the capacity to cleave the sugars to derive energy for themselves.

Instead of painstakingly culturing each microbe found in the gut, Wither’s and his team employed a process called metagenomics. This allows you to collect all the DNA for all the microorganisms at once, and then use this to select for genes that code for enzymes that cleave mucins. Over 20,000 DNA samples were taken, and from this 12 enzymes were found that qualified, and some that can cleave type A blood up to 30 times more effectively than the previous candidates.

The team combined their newly discovered enzymes with previous enzymes that cleave type B antigens, and now they had a tool that could convert A, AB and B blood into type O, a huge step forward.

Researchers have attempted to make enzyme-altered blood before, and there was even a human trial in 2000, but the enzyme used could only convert type B blood and was found to be too expensive and inefficient for widespread use. These glycosidases are highly efficient, meaning less is required so the cost is hugely reduced, and then less has to be filtered out during the processing.

To prevent spreading infectious diseases, RBC donations are never pooled and treated en masse, so altering the blood would need to happen one donation at a time. This has proved to be another issue for previous candidates, but Withers’ enzymes could be added directly to the donation bag. It can then get to work while it is sitting in the donation bank, and then removed during the processing step.

To create a truly universal blood type, the Rh antigens must also be removed, but this technique shows really exciting potential.

The demand for blood is higher during the festive period, so please take some time out of your day to make someone else’s 😊

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