Researchers Discover Gut Bacterial Enzymes that Convert Type A to ‘Universal’ Type O Blood

By Rajaneesh K. Gopinath, Ph.D.

In a major breakthrough, researchers from the University of British Columbia in Vancouver, identify an enzyme pair from an obligate anaerobe through their functional metagenomic screening of the human gut microbiome. The discovery is expected to significantly impact blood transfusion procedures in the future.

The World Health Organization (WHO) reports that about 117.4 million blood donations are collected worldwide and there has been a considerable increase in the number of blood donors over the past decade. This only reaffirms the fact that blood transfusions continue to be pivotal for the majority of clinical procedures. However, only a very few of the eligible population volunteer to donate and the shortage of blood and blood components (especially platelets) still exist.

The ABO blood group

Just like so many other genetic traits, we inherit blood type from our parents. The terminal sugar molecules (antigens) present on our RBCs determine our blood type and it governs donor compatibility in the event of a lifesaving blood transfusion procedure. ABO and Rh are the two main blood group systems among which the former has four main types; type A, B, AB or O. While individuals with blood type A and B contain their respective antigens, the type O has neither and hence becomes a universal donor. When blood from a type O individual is transfused to a recipient of the same rhesus type (Rh + or -), no immune reactions are incited and is therefore much sought after.

The ECO‐RBC concept

In order to solve the problem of blood shortage in an emergency and to minimize the time consumed because of blood typing, scientists have labored over three decades to find ways to eliminate blood group antigens. Of the three main antigen‐modulation strategies undertaken, the manipulation of the ABO system is the most preferred. As early as the 1940s, scientists discovered that certain microbes displayed enzymatic activity that could alter the ABO blood type.

However, only in the 1980s a practical technology called ‘Enzyme Converted group O Red Blood Cell’ (ECO‐RBC) concept was developed by Goldstein and Lenny of the New York Blood Center for enzymatic conversion of the A and B antigen. More recently, ZymeQuest did a mass screening of bacterial and fungi extracts and identified the enzymes N‐acetylgalactosaminidase derived from Elizabethkingia meningoseptica and a α‐galactosidase derived from Bacteroides fragilis for the conversion of type A and B into O respectively.

The New Study

At this juncture, researchers from the lab of Stephen G. Withers at the University of British Columbia (UBC), Canada have now identified an enzyme pair, a N-acetylgalactosamine deacetylase and a galactosaminidase from the gut bacteria Flavonifractor plautii. The authors demonstrate that the new found enzymes are 30% better in converting type A to type O blood as compared to the ones previously identified. Nevertheless, it requires further research to improve its efficiency and advance it to practical use. The study was published in the journal Nature Microbiology and coincidentally falls close to the eve of world blood donor day on June 14th.

References

1. https://www.nature.com/articles/s41564-019-0469-7
2. https://onlinelibrary.wiley.com/doi/full/10.1111/j.1365-2141.2010.08561.x
3. https://www.nature.com/articles/nbt1298
4. https://onlinelibrary.wiley.com/doi/full/10.1111/j.1423-0410.2007.01003.x
5. https://www.sciencemag.org/news/2007/04/not-your-type-dont-sweat-it

Author

Rajaneesh K. Gopinath