Although millions of liters of blood are donated worldwide every year, not every patient can benefit immediately because of blood groups. Blood group O however, as a universal donor is, therefore, particularly in demand. Researchers from Canada have now succeeded for the first time in generating blood group O from blood group A using microbial enzymes.
A recent study presented a possible way to produce the universal blood group O donor simply from blood group A in the future. Bacteria from the intestinal microbiome provide everything it apparently needs to do this.
The ABO blood group system contains the blood groups A, AB, B, and O, which are mainly characterized by certain glycosylated protein chains on the surface of erythrocytes. Since people of blood group A, for example, have antibodies against the surface molecules of blood group B, their blood samples cannot be substituted. For this, the same blood groups or the "emergency blood group" O are required, the latter being regarded as a universal blood donor.
It has been known for quite some time that bacteria in the human intestine have very similar surface characteristics that may allow them to interact with blood groups. The intestinal bacterium Flavonifractor plautii also contains two enzymes that are able to split blood group-defining surface molecules, according to the researchers of the current studies from Canada.
These enzymes are not primarily blood group antigen splitting enzymes, but they are "accidentally" able to degrade the glucosamines (N-acetylgalactosamine) of blood group A in the laboratory. In the end, this degradation resulted in blood group O, the so-called H antigens.
It is interesting to note that the enzymes can be easily removed from the blood products even after work is done so that no uncontrolled reaction in the recipient organism is to be feared. Such conversion from blood group A to blood group O would also be a very advantageous option if it were possible to avoid a shortage of blood reserves of the universal donor group O in the future. Approximately 40% of people carry blood group O, and another 40% have blood group A.
Rahfeldt P et al., An enzymatic pathway in the human gut microbiome that converts A to universal O type blood. Nature Microbiology 2019.