Scientists are closing in on a way to transform any type of donated blood into type O, the universal blood type that can safely be given to any patient.
Researchers have created a special enzyme that can shear off the substances on red blood cells that are responsible for potentially fatal immune reactions if a patient receives the wrong type of blood, according to a new study.
The enzyme is not yet effective enough to allow for large-scale processing to convert type A or type B blood into type O, said lead author David Kwan, a postdoctoral fellow of chemistry at the University of British Columbia's Centre for Blood Research in Vancouver, Canada.
"We're not there yet. This is really a step towards that," Kwan said. "The big thing is that we've shown that it's feasible to improve these enzymes."
The effect of a technology that could convert any blood type to the universal donor type O would be "transformational" for the world's blood supplies, said Dr. Richard Benjamin, chief medical officer for the American Red Cross.
Blood banks tend to lean heavily on donors who are type O, particularly if their blood also is RH-negative, Benjamin said. Type O, RH-negative blood can be used by anyone, regardless of their blood type.
About 11 percent of hospital transfusions involve donated type O, RH-negative blood, even though only about 6 percent of the population carries that specific blood type, Benjamin said.
"We are in constant short supply of that type, and we are frequently going to those donors and asking them to give blood," Benjamin said. "We've pestered them a lot, actually."
Blood types are determined by antigens, which are sugars on the surface of red blood cells. These antigens can cause an immune system reaction if a person's body recognizes them as foreign, and that's why a person with blood containing type A antigens cannot donate to a person with type B blood.
A process that uses enzymes to strip away these antigens has been around for about 15 years, Benjamin said, but until now the process has not proven effective enough. Clinical trials from the early 2000s found that blood treated with the enzymes still contained enough antigens to produce a muted immune response.
Kwan and his colleagues performed directed evolution on the enzyme, generating mutant versions and selecting the ones that did the best job of stripping away blood antigens.
In just five generations, the enzyme became 170 times more effective -- not yet effective enough to solve the problem, the researchers said, but improved enough to show that the process of improving the enzyme does work.
"We're not ready to use this on a practical clinical scale yet," Kwan said. "You need to nearly completely remove all of the antigens. We can get most of them off of the blood cells, but if you have a mismatched blood type you still will have an immune reaction."
It will take years at least to develop the enzyme enough to create type O blood from type A or type B, he said.
And once they have an optimized system for converting blood, they will need to go through clinical trials in the United States and get a license from the U.S. Food and Drug Administration, Benjamin said.
"If they're not in the clinic yet, that's a five- to 10-year horizon," he said.
Once perfected, the same process might also be turned toward helping bodies accept other donations, such as organ transplants, Kwan said.
"These same antigens we're trying to cleave off of red blood cells are also present on other tissues and organs that can be transplanted," he said.
However, there is one big difference -- organs are living tissues, and they might regenerate any antigens that can be stripped by the enzymatic process, Kwan said.