The process is safe, efficient and cost-effective, researchers report.
By Thomas H. Maugh II
Times Staff Writer
April 2, 2007
Researchers have perfected an inexpensive and efficient way to convert types
A, B and AB blood into type O, the universal-donor blood that can be given to
anyone — an achievement that promises to make transfusions safer and to
relieve shortages of type O blood.
The team reported Sunday in the journal Nature Biotechnology that it isolated
bacterial enzymes that safely remove from red blood cells the sugar molecules
that provoke an immune reaction in the recipient.
Previous studies of type O blood produced from type B by a different method
have shown it to be both safe and effective, and the researchers are now
conducting clinical trials with the new product.
Mismatching of blood causes at least half of all transfusion-related deaths.
And the need for precisely matched blood is behind the costly and inefficient
process of shuttling blood units back and forth between regional blood banks
and hospitals to match daily requirements.
"Those issues could be largely resolved if there were a universally
transfusible blood supply," said Douglas L. Clibourn, chief executive of
ZymeQuest Inc. in Beverly, Mass., which is developing the technology.
The problem involves sugar molecules on the surface of red blood cells. Type A
blood has one set of sugars and type B has another, whereas type O has none.
People with type A blood have antibodies against the type B sugars, people
with type B have antibodies against type A, and people with type O have
antibodies against both.
If a person receives mismatched blood, the antibodies attack red blood cells,
producing a potentially fatal breakdown of the cells.
In the 1980s, researchers isolated an enzyme from coffee beans that could
convert type B to type O. Clinical trials of the enzyme-produced blood showed
it behaved no differently from normal blood in hospitalized patients.
But the enzymes involved were very expensive and had to be used under highly
acidic conditions that damaged the red cells. And the research team could not
able to find an enzyme that would convert type A to type O. So development was
halted.
ZymeQuest commissioned cellular biologist Henrik Clausen of the University of
Copenhagen to search for new enzymes to carry out the conversion.
Clausen and his team investigated more than 2,500 bacteria and fungi before
they identified the two candidates that were cited in the Nature Biotechnology
report.
The discovery could be a major breakthrough in improving the blood supply,
wrote Geoff Daniels of Britain's Bristol Institute for Transfusion Sciences in
an editorial accompanying the article.
The new enzymes are 100 to 1,000 times more potent than previously used ones
and, more important, they work at room temperature and neutral pH, which is
very good for blood cells, said Dr. Martin L. Olsson of Lund University in
Sweden, who is overseeing the clinical trials. In an hour, the enzymes remove
all the sugar molecules from the surface of red blood cells, after which they
can be easily washed away.
The team initially isolated blood from healthy individuals, converted the red
cells to type O and injected them back into the donors, said Olsson.
After that study showed no problems, they began a larger clinical trial using
donor blood. Olsson said there had been no adverse reactions to the product;
he would not comment further on the results.
Clibourn said he expected results from the trial to be available later this
year.
If the trials are successful, ZymeQuest will manufacture a system that can be
used by blood banks and hospitals to convert donor blood into type O as
necessary.
