Enzymes Allow Type A Blood to be Converted to a Universal Donor for Use in Hospitals

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The World Health Organisation estimates that 100 000 000 blood bags are required worldwide for blood transfusions every year. Transfusions are essential in restoring a patient’s red blood cell count which is important when treating a medical condition like anemia, during surgery or after childbirth.

However, transfusions can run into complications if the blood of the donor doesn’t match the blood of the recipient; this means the blood contains different types of antigens and will react with antibodies found on red blood cells if they are mixed, which causes an allergic response and the blood to clot together. To overcome this, all donor blood is tested beforehand, and a patient is only given the same blood type as their own. The only type of blood which is safe to give to any patient, even if their blood type is unknown, is O negative: the universal blood type.

O negative blood contain no antigens, meaning antibodies on red blood cells from the recipient’s blood have nothing to bind to and won’t cause any adverse reaction. This is especially useful in an emergency where there is no time to check blood type, as O negative can be given and there won’t be a risk of reaction. However only 13% of donors for the NHS are O negative, which means it isn’t available for universal use; this limits the supply drastically, and the NHS state that it’s a “constant challenge” to collect enough to meet the demand. In contrast blood type A is the second most common blood type and A positive makes up 30% of donors. Due to being readily available, there has been substantial work focused on removing the antigens found in type A blood in order to convert it into a universal donor blood type.

Biochemist Stephen Withers and Postdoctural researcher Peter Rahfeld from UBC, concluded the best place to find something to break down human blood was within humans. Thus, they investigated the gut microbiome community in humans using a technique called functional metagenomics. Bacteria in the gut gain most of their energy by cleaving large glycoproteins called mucins- a similar structure to A-defining antibodies. Withers and Rahfeld screened the enzyme activity of the bacteria in the gut with a mucin-like substrate that produced fluorescence when cleaved; this identifies which bacteria contain enzymes able to cleave the glycoprotein. This screening found two enzymes that originated from the gut of the bacteria Flavonifractor plautii, that were able to cleave the sugars and have since been proven to cleave antibodies in human blood as well. This research was theorized and attempted for years before Withers and Rahfeld executed it and is now being credited as a major breakthrough in the medical field as statedĀ  by blood transfusion experts like Harvey Klein.

However some scientists remain more skeptical and are keen to see the long term effects of this research in medicine. A risk with recent studies like this one is how little we know about other possible long term effects, something that is acknowledged by Withers. Withers recognizes the potential of other molecules being removed from the blood cells by the enzymes as a side effect and how we currently cannot determine possible effects of this. Despite concerns, the potential this research has unlocked is undeniable; work can now be focused on altering other blood types such as type B and type AB to be universal donors too. Before Withers and Rahfeld’s study, this wasn’t a possibility, but further clinical testing and screening will decide how many applications their work has in the world of medicine.

Read more about their work in the original article by Elizabeth PennisiĀ  here, and the original journal article from Nature Microbiology here.

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