Blood is crucial to healthcare, and as the population of the world ages, more medical procedures are being performed and the demand for donor blood is rising. There are sugar groups or antigens on red blood cells that create different types of human blood known as A, B, AB, and O. The antigens determine which blood types are compatible with each other, and some cannot be mixed. Otherwise, a life-threatening immune reaction can happen if the wrong blood type is given to a person.
Healthcare facilities need an ample supply of different types of blood so that all patients can be helped when they need it. But once donor blood is screened for diseases and typed, it can only be stored under refrigeration for 42 days until it expires and cannot be used anymore. If a universal donor blood could be developed, it would reduce problems, costs, and challenges in the blood supply that come from needing four different kinds of blood; such as having enough of the rarer types for all patients. Universal blood could also cut down on waste.
Scientists have now identified enzymes that come from human gut bacteria, and can remove the sugar molecules that create the A and B antigens in human ABO blood types. The work has been reported in Nature Microbiology.
"For the first time, the new enzyme cocktails not only remove the well-described A and B antigens, but also extended variants previously not recognized as problematic for transfusion safety. We are close to being able to produce universal blood from group B donors, while there is still work to be done to convert the more complex group A blood," noted Professor Maher Abou Hachem of Denmark Technical University.
Now the researchers want to identify any potential obstacles and improve the enzymes so that universal blood can eventually be produced, added Hachem.
Researchers have been searching for decades to find the right enzymes to strip antigens from red blood cells and make universal donor blood. While some enzymes that are able to remove the A and B antigens have been identified, the enzymatic reactions are not efficient enough to completely remove the antigens and stop any and all immune reactions that can be triggered by the blood. So these enzymes are still not used in practice.
But a human gut microbe called Akkermansia muciniphila, which breaks down mucus, produces a combination of enzymes that are exceptionally good at removing sugar groups on intestinal mucosa. These groups are very similar to antigens on human blood cells, and the researchers suspected these enzymes might work to remove the A and B human blood cell antigens.
"This hypothesis turned out to be correct," said Hachem.
The investigators have already submitted a patent application on the process and are continuing to work on it. The concept will have to be tested in trials, but could eventually be used in healthcare.
Sources: Technical University of Denmark, Nature Microbiology
