Thursday, April 05, 2007

Blood shortages to be passé?

Hallelujah! Blood shortages may be passé!

Such were the headlines this past week with a flurry of news items about bacterial enzymes that can cut antigen-bearing sugar molecules from the surface of red blood cells. The enzymes can render A and B rbc into group O rbc, producing so-called "universal donor" cells that can be transfused to recipients of any ABO group, providing the rbc are Rh-negative and providing recipients lack unexpected antibodies.

The news was based on this recent publication by Danish researchers:

Was it really news given that the concept has been around for about 25 years? For example:

Editorials back then were similar to today:
Cowart VS. Green coffee beans may solve a blood bank problem. JAMA 1982 Jan 1;247(1):12.

Similar research followed in the 1990s:

Looking back, I think that I first became aware of the possibility of enzymes to cleave ABO blood group antigens in this 1994 paper and accompanying editorial:

These early papers made nice discussion papers for students as they dealt with enzymes from coffee beans, soybeans, and taro (novelty) and helped reinforce the sugars responsible for group A and B antigens.

My joke when teaching ABO blood group chemistry was that no one in the transfusion service ran around asking for a crossmatch for two alpha-D-galactose red cells. <8-)

One problem was that the research dealt with converting B cells into group O red cells (stripping the terminal alpha-D-galactose) and would be more useful if A rbc could be converted using a naturally occurring alpha-N-acetylgalactosaminidase, since group A has a higher frequency in Western Europe and North America.

Another was that the research could not be applied to large scale production despite in vivo studies such as this one:

In a way, the current headlines remind me of the unmet promise of "artificial blood substitutes" (perfluorocarbons and hemoglobin-based oxygen carriers) whose history dates back to the 1960s. We have been waiting a long time!

Many of the news items on the possibility of converting other blood groups to group O include precautions. As noted by Ian Franklin, the national medical and scientific director of the Scottish National Blood Transfusion Service, in the Scotsman:

Quite an understatement by Dr. Franklin. Moreover, the conversion process would need to be cost-effective when applied to large-scale production (millions of blood donors annually).

So, will blood shortages may be passé any time soon? My guess is that this French saying applies:

Keep on donating!

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1 comment:

  1. Anonymous1:45 AM

    I agree that this technique is a long way from being routine and used on a large scale. Clinical trials to assess the long term effects would also be important. Would antibodies be formed to neo-antigens due to the enzyme treatment?
    All other blood group antigens apart from the A/B will be present and so it will not reduce the incidence of alloimmunisation or delayed TR's for example. Plus, I think it will increase the BTS laboratory workload because all blood will need to be tested twice, before and after treatment, to ensure that no A/B antigens are left on the cells. Cost-effectiveness will need to be carefully assessed! Although even one fatality due to an ABO incompatible transfusion is one too many, if efforts (and money) are concentrated on training and education so that ABO typing is 100% guaranteed, then this may be a wiser distribution of funds!
    'ECO'cells would of course, be useful in emergency situations and in times of conflict/terrorist activities but it remains to be seen how easily the research will convert to rotuine preparation, even for these situations.

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