Hospitals must always maintain a supply of the various blood types that patients might need, and right now there is a critical shortage; the Red Cross is asking for donors. About 16,500 liters are used every day in the United States. Now researchers have found a way to convert type A blood to type O, the type that’s most universally accepted. Two microbes that typically live in the human gut were found to produce enzymes that can make the conversion, which could help build a bigger supply of useful blood. The findings have been reported in Nature Microbiology.
“This is a first, and if these data can be replicated, it is certainly a major advance,” Harvey Klein, a blood transfusion expert with the National Institutes of Health’s Clinical Center who was not involved with the work told Science.
Molecules on the surface of red blood cells called antigens are what gives a person a blood type. There are four major blood types - A, B, AB and O. If type B blood is given to a person with type A blood, or vice versa, the recipient’s immune system will launch an attack against the donated red blood cells, which can be deadly. Red blood cells from a type O donor don’t have the antigens to stimulate such an attack and can therefore be used as a donor for recipients with any blood type.
In the emergency room, clinicians often don’t have time to check for a person’s blood type before giving them a blood transfusion, so universally compatible type O blood is important to have on hand. Type A blood is more common than type B, and scientists have tried to remove antigens from type A blood before in an effort to generate more universal donor blood, but previous efforts haven’t been efficient.
Scientists in the lab of Stephen Withers, a chemical biologist at the University of British Columbia (UBC) started looking to the many microbes that inhabit the human gastrointestinal tract to find a good enzyme that can remove type A antigens. Microbes in the gut are known to generate enzymes that chomp on molecules that are similar to red blood cell antigens.
A metagenomic screen revealed a pair of enzymes that the gut microbe Flavonifractor plautii produces. Very low levels of the enzyme were able to convert type A blood to type O blood.
Additional work will be required before this process can be implemented. The researchers have to ensure that the offending type A antigens have been removed entirely, which has been another problem that hampered previous work. They also have to check the red blood cells completely to be sure that nothing else has been changed.
Learn more about the current shortage of blood, and how blood donors save lives from the video.