Scientists have discovered enzymes that can make blood of any group universal in transfusion

A group of researchers from Sweden and Denmark identified a mixture of enzymes capable of converting blood of any group — A (II); B (III) or AB (IV) — to the O (I) group suitable for transfusion.

The research was published in the scientific journal Nature Microbiology.

A mixture of enzymes produced by bacteria from the human gut, when mixed with red blood cells, can destroy antigens A or B, converting red blood cells into the universal type O.

Blood type is determined by molecules of two different types that can be present on the surface of red blood cells. These molecules-antigens are conventionally designated A and B. Typical combinations of antigens form four blood groups: O (I), A (II), B (III), AB (IV). Type O blood has neither A nor B.

These antigenic molecules determine compatibility between donor and recipient for safe blood transfusion and organ transplantation.

Immune systems that have never seen A or B antigens will attack and destroy these cells as soon as they enter the body in a transfusion. This can lead to serious consequences for the recipientʼs health and even death. Because type O (I) blood does not have any of these antigenic molecules, it is suitable for transfusion to almost anyone.

Because of this versatility, the blood supply of group O (I) is quickly exhausted, so it is often in short supply, in particular in emergency cases, when doctors must act immediately without knowing the patientʼs blood group.

The conversion of red blood cells to universal type O is not a new idea. For the first time, such a technique was presented back in 1982, when scientists discovered an enzyme extracted from green coffee beans that could deprive erythrocytes of group B of their antigen.

But this enzyme did not seem to be very effective, which made the wide application of this method impractical. In addition, there were doubts about the safety of this method. For unknown reasons, donor blood sometimes remained incompatible with recipients, even though the donor cells were devoid of almost all antigens.

Subsequently, scientists returned to researching this method and in 2019 discovered other enzymes produced by intestinal bacteria.

Based on previous work by other teams, the researchers selected several candidate enzymes produced by the intestinal bacterium Akkermansia muciniphila. Danish and Swedish researchers tested 24 enzymes, treating hundreds of blood samples with them. Enzymes have proven to be extremely effective and have shown good results in research.

The Scandinavian researchers note that more work needs to be done to improve the destruction of antigen A. In addition, scientists have yet to understand why a small proportion of red blood cells still cross-react with group O (I) plasma.

• In 2022, researchers used a similar strategy (with different enzymes) to convert the blood type of donor lungs from A (II) to universal O (I) in the laboratory.