The Telegraph
Since 1st March, 1999
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Breakthrough in blood conversion
- Scientists transform A and B into universal using ‘molecular scissors’

New Delhi, April 2: Using bacterial enzymes as molecular scissors, scientists have developed a technology for efficient conversion of blood groups A and B into the universal which can be given to anyone.

An international research team today announced that it has used novel bacterial enzymes to develop a simple process to produce red blood cells of the universal group , a feat that promises to alleviate blood shortages.

Although conversion of blood from one group into another was first proposed more than 25 years ago — and even routinely demonstrated in the laboratory — the conversion of blood groups for transfusions has remained impractical. Now Henrik Clausen of the University of Copenhagen and his colleagues have identified enzymes called glycosidases from two species of bacteria that can do the job quickly and efficiently.

In a report published in the journal, Nature Biotechnology, the researchers said enzyme-converted universal red blood cells could “improve the blood supply and enhance the safety of transfusions”.

“We believe this is very important for transfusion medicine because there’s usually a shortage of blood,” said Gerlind Sulzenbacher, a biophysicist at the University of Marseilles in France.

Blood cells gain their identity as A, B, AB, or through chain-structured sugar molecules that stick out of the cell surfaces and have unique terminal ends. The removal of the terminal ends of the sugar chain from A or B converts it into .

The conversion, however, does not alter another surface molecule — the Rh factor — which is also important for transfusions. Blood transfusions have to be compatible in terms of both ABO groups and Rh factor, which can be positive or negative.

While blood group can be given to anyone, the transfusion of A or B to patients who have antibodies to these groups can trigger severe, sometimes fatal, reactions.

The scientists screened 2,500 fungi and bacteria and identified two species — Elizabethkingia meningosepticum and Bacteroides fragilis — that make enzymes that can function like scissors to cut off the terminal ends of A and B.

“The glycosidase enzymes chop off the terminal ends very efficiently,” Sulzenbacher told The Telegraph.

Her role in the project was to determine the 3-D structure of the enzymes. “Although conversion of blood groups has been shown earlier, the significance this time is efficient conversion technology,” Sulzenbacher said.

A US-based company, ZymeQuest Inc, which collaborated in the research, has developed technology that allows each blood unit to be completely transformed.

The blood gets converted after it is “incubated” with the enzyme for about an hour, Sulzenbacher said.

The process also removes the enzyme after conversion to ensure that recipients will get blood with no trace of the enzyme.

Transfusion medicine experts said the technology appears a “big step” towards alleviating blood supply shortages, but cautioned that clinical trials would need to be done to establish safety and efficacy of the converted blood.

“Scientifically, it would be a major feat, but I think we’ll have to wait a while to determine its impact on clinical practice,” Dr Anna Thomas, a senior blood bank officer at the Breach Candy Hospital in Mumbai, said.

Scientists had first demonstrated conversion of blood to group in 1982, using enzymes from green coffee beans. However, the process was inefficient and too impractical to be used on the scale required for transfusion medicine.

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