This situation is often faced by patients when they are rushed to a hospital for a blood transfusion — they don’t have their blood type. Scientists have been trying to solve this problem since many years, and now they have finally made a breakthrough. By making alterations to an enzyme to cut off the antigens from types A and B blood, scientists have managed to make it more like the universal donor type O. Read the complete study in the Journal of the American Chemical Society.
Basically A and B antigens are sugars that are conveyed to the surface of red blood cells—it’s their combination—with blood cells encompassing one, all, or none of these antigens—that generate the four main blood types: A, B, AB, and O. And this in turn determines which blood you can accept and who you can give blood to. As type O have neither antigen it can be injected to anyone, but all other types can trigger life-threatening immune reactions if injected to the wrong patient.
Back in 1980s a team in New York was able to show that an enzyme extracted from green coffee beans was able to remove B antigens from red blood cells; so, the idea of converting blood types has existed since decades. Via clinical trials scientists confirmed that blood could be safely transfused to people of a different blood group; but, the enzyme reaction lacked the efficiency needed, requiring a very huge volume at too high a temperature to convert all the blood cells to make the process viable.
Nonetheless, the enzyme developed by scientists from the University of British Columbia could potentially solve this problem. The enzyme simply cuts off the problem antigens, to effectively turn A and B blood into type O. Steve Withers, one of the researchers explains it like this:“The concept is not new but until now we needed so much of the enzyme to make it work that it was impractical. Now I’m confident that we can take this a whole lot further.”
The process employed to create the enzyme is called “directed evolution”. A method of protein engineering, it hinges on natural selection, letting a user evolve a protein, such as an enzyme, towards a desired goal. Scientists first took an original enzyme, and then inserted mutations into the gene that codes for it. By picking the mutants that were most efficient in removing the antigens, and repeating the process again and again, the researchers managed to make the enzyme 170 times more effective over just five generations.
“We produced a mutant enzyme that is very efficient at cutting off the sugars in A and B blood, and is much more proficient at removing the subtypes of the A-antigen that the parent enzyme struggles with,” said David Kwan, the lead author of the study and a postdoctoral fellow in the Department of Chemistry.
Their work is not over yet. Although the enzyme managed to remove the vast majority of antigens from type A and B blood, it was not able to remove all of them. Since our immune system is highly sensitive to blood groups—so much so that even small amounts of residual antigen can trigger an immune response— the scientists first of all have to be sure that all antigens are absent.