Toward Universal Whole Blood in the Battlefield

Blood transfusions are an essential part of modern medicine and have saved countless lives. They are used as support for a number of medical operations, but most dramatically they are essential in cases of severe blood loss caused by traumatic injuries. In military situations, the major cause of preventable loss of life is through blood loss from serious wounds, requiring replacement of lost fluid. Fresh whole blood transfusions are the best way to do so, and have a long history in medical care on the battlefields, starting in 1917 and continuing in the Second World War with Field Blood Banks that allowed donation of fresh whole blood from other Soldier donors close to the point of injury. This practice has continued, with some modifications, in all subsequent conflicts.

However, blood must be transfused with great care, as there are four major types — A, B, AB, and O — and, in general, blood of a particular ABO type must be given only to a person of the same blood type. While other blood groups exist, the ABO types are the most critical. If blood of the wrong type is transfused, this can lead to serious consequences, including red blood cells bursting, and blood thickening — fatal in 10 percent of cases, even in a hospital setting. The only exception to this rule is O-type blood, which can be given to people of all blood types. It is thus known as 'universal donor' blood and is used in emergency situations when the blood type of the patient is not known.

The underlying cause of blood-type differences is a set of sugar molecules known as antigens, which are attached to the surface of the red blood cell. A-type blood has a specific sugar (GalNAc), whereas B-type blood has a similar but different sugar (Gal). O-type blood has neither. Thus, if the GalNAc or Gal sugars could be removed from their surfaces, the A- and B-type red blood cells would be converted to O-type red blood cells and could be used as 'universal donor' blood.

Our laboratories have discovered enzymes within the human gut microbiome that can do exactly this. They act like precise molecular scissors that cut off just these sugar molecules, and thus can be used to convert A and B red blood cells to O-type. We plan to use these enzymes to convert whole blood in this way by simply adding them to the blood collection bag. We shall then explore the properties and safety of this converted blood to make sure it does not result in any bursting of red blood cells when mixed with other blood or change its blood clotting properties.

Before this converted blood can be transfused into a patient, we need to remove the added enzymes. To do this we shall develop and thoroughly test a capture device to specifically bind to the enzyme molecules and immobilize them on its surface. This capture device will be placed within the tubing leading from the bag to the patient.

Equipped with these modified blood conversion bags containing our enzymes and capture device, the field medic could harvest blood from any fit Soldier, regardless of blood type, and convert it to O-type. This could then be transfused safely to any injured Soldier without the medic needing to know his or her blood type. This technology would also find application in civilian settings, in situations where there is no time, or capability, to determine blood types, such as after gunshot wounds or car crashes. The approach has the potential to save countless lives.