According to the ABO blood group system, there are four main blood types in humans. These are A, B, AB, and O.
Of these, only O is a "universal donor," meaning that a person with this blood type can safely donate blood to all the other groups.
Otherwise, people with type A can only donate to people with types A and AB, type B to types B and AB, and type AB only to other ABs.
Blood type compatibility is therefore very important in cases of mass disasters, when those affected need a constant supply of blood from compatible donors.
If there was an appropriately large supply of the "universal donor," however, this would make it easier to attend to anyone in urgent need of a transfusion.
For years, researchers have been looking into effective ways of converting other blood types into type O by developing enzymes that would remove the antigens that make blood types A, B, and AB so "discriminating."
Now, researchers from the University of British Columbia — with branches in both Vancouver and Kelowna, Canada — have presented the results of a new study at the 256th National Meeting & Exposition of the American Chemical Society, held in Boston, MA.
They explained that they may have found an effective and safe way of converting blood types A and B into type O: by using certain enzymes found in the gut.
"We have been particularly interested," says study co-author Stephen Withers, "in enzymes that allow us to remove the A or B antigens from red blood cells," adding:
"If you can remove those antigens, which are just simple sugars, then you can convert A or B to O blood."
Gut enzymes that can 'transform' blood
Withers and team used a method called "metagenomics" to identify promising enzymes that may be able to act on blood in such a way as to render it universally safe and useable.
"With metagenomics," he points out, "you take all of the organisms from an environment and extract the sum total DNA of those organisms all mixed up together."
Next, the researchers used the bacterium Escherichia coli to determine which types of DNA were able to code enzymes able to remove simple sugars, such as the blood-type specific antigens (immune-triggering substances) that determine blood group incompatibility.
"This is a way of getting that genetic information out of the environment and into the laboratory setting and then screening for the activity we are interested in," notes Withers.
The scientists' analysis revealed that certain enzymes found in human gut microbiota are able to turn blood types A and B into type O by removing their specific antigens. These enzymes, they add, act with 30 times more efficiency than others previously considered for the same purpose.
Withers and colleagues explain that the gut wall in humans hosts a special type of protein called "mucins," which contain simple sugars that allow gut bacteria to attach.
Some of these sugars, they explain, are similar to the antigens found in blood types A and B. To find the enzymes that would help them remove the blood antigens, the researchers looked at which enzymes gut bacteria used to absorb the mucin sugars.
'A very interesting candidate'
At present, Withers and colleagues are looking to test the isolated enzymes on a larger scale, with a view to eventually setting up clinical trials.
"I am optimistic that we have a very interesting candidate to adjust donated blood to a common type," explains Withers.
"Of course," he goes on, "it will have to go through lots of clinical trials to make sure that it doesn't have any adverse consequences, but it is looking very promising."
Below, you can watch a presentation explaining why it is important to find an effective means of converting other blood types into type O, and how the researchers went about conducting their recent study.