 |  | 
Published online: 1 April 2007; | doi:10.1038/news070326-17
Blood made suitable for allStripping blood of antigens means it can be given to anyone.Alison Abbott 
| Anyone can receive O type blood, but stocks constantly run low. Getty |
|
Scientists
have discovered enzymes that can efficiently convert blood groups A, B
and AB into the 'universal' O group — which can be given to anyone but
is always in short supply.
The
two novel glycosidase enzymes were identified in bacteria by an
international team led by Henrik Clausen of the University of
Copenhagen in Denmark. The researchers hope that the enzymes will both
improve the erratic supplies of blood around the world, and also the
safety of transfusions. Clinical trials to test the safety and
effectiveness of their converted blood are being planned.
The
ABO blood-type system is based on the presence or absence of the
sugar-based antigens 'A' and 'B' on red blood cells. Type O blood cells
have neither A nor B antigens, so may be safely transfused into anyone.
But types A, B and AB blood do, and cause life-threatening immune
reactions if they are given to patients with a different blood group.
The bacterial glycosidase enzymes strip these antigens away from A, B
and AB blood.
The
idea of such antigen-stripping goes back to the early 1980s, with the
discovery of an enzyme in coffee beans that removes B antigens from red
blood cells1. Early-stage clinical trials
showed that the converted blood could be safely transfused into
individuals of different blood groups; no traces of enzyme or antigen
remained to cause reactions2. But the enzyme reaction was far too inefficient to make large-scale conversion practical.
Clausen's
team screened 2,500 extracts from different bacteria and fungi for
their ability to cleave off A and B antigens. The newly discovered
bacterial 'B' enzyme is nearly 1,000 times more efficient then the
coffee-bean B enzyme — the additional discovery of an enzyme to remove
A antigens means that all blood types can now be converted. The work is
reported in Nature Biotechnology3.
 The biggest advantage [is] eliminating incidents of giving the wrong blood  |
Martin Olsson, Lund University Hospital Blood Centre
|
|
| | |
Common stock
Type
O is the most common blood group, but stocks constantly run low because
it is used in all emergency situations where there is no time to
determine the patient's own group.
An
additional pressure on type-O blood, particularly in the United States,
comes from the mismatch between blood donors and recipients. Most US
donors are Caucasian, amongst whom 45% of people are blood group O. But
more than half of African Americans, and nearly all native Americans
are O, and so require type-O blood.
Also
the donor population is shrinking as fears of transfusion-transmitted
infections of new diseases such as SARS, mad-cow disease and West Nile
disease remove from the pool donors who may have been exposed.
"Restrictions
are getting almost comical," says Martin Olsson, head of the Lund
University Hospital Blood Centre in Sweden, and a member of the
international team. "At different times, the US excluded from donation
those who had recently visited Europe in case they had contact with
BSE, and Europe has excluded those who recently visited the US where
they perceive a higher risk of HIV."
Yet
in practice the greatest risk in blood transfusion is not the
transmission of disease but the accidental transfusion of the wrong
blood group, he says. "As a clinician, I see the biggest advantage of
the new enzyme technology as eliminating incidents of giving the wrong
blood."
The
Boston-based company ZymeQuest is developing the enzyme technology for
commercial use in blood centres. Early-stage clinical trials are
underway. If all goes well, blood centres could be using the
technologies in just a few years.
References
- Goldstein J., et al. Science,
215
.
168
-
170
(1982). | Article | PubMed | ChemPort |
- Lenny L. L., et al. Transfusion,
35
.
899
-
902
(1995).
- Liu Q. P., et al. Nature Biotechnol., doi:19.1038/nbt1298 (2007).
|
| | |
| |
|
