Approximately 4% of patients who are candidates for blood transfusion have irregular antibodies in the serum that direct against red blood cell antigens that can cause an acute hemolytic transfusion reaction. This percentage may be as high as 38% in patients with specific pathologies or polytransfusion. Something similar occurs with 10% of pregnant women, who are at risk of becoming sensitized to erythrocyte antigens of the fetus inherited from the father. These women are at risk of inducing Hemolytic Disease of the Fetus or Newborn (EHFR), which in the most severe cases, requires transfusion of red blood cells in utero or postpartum.

To detect anti-erythrocyte antibodies before a transfusion and during gestation, to avoid these reactions in time, clinicians use panels of red blood cells that recognize these antigens, which proceed from well-characterized blood donors in a very meticulous work of analysis, selection, and panel constitution. This process is extremely laborious because the panel must include red blood cells that are capable of recognizing even the rare, low-incidence antigens, which are the most difficult to detect. Added to this complexity is the limited life of the red blood cells, which forces to fit the extractions of the donors in a pre-established calendar to include the different combinations of cells that make up a panel in adequate time for their use.

As a promising alternative, the Blood and Tissues Bank of Catalonia (BST) has undertaken the ID-VITRORED project, led by Dr. Núria Nogués, with the participation of Pablo Menéndez and his group from the Josep Carreras Institute. ID-VITRORED consists of developing a panel of induced pluripotency cell lines (iPSCs) from donors with selected phenotypes. That is to say, to have an inexhaustible bank of cells produced in the laboratory with the antigens that will recognize these antibodies, without the need to obtain them from donors.

The way to make these cells express the erythrocyte phenotype of interest is through gene-editing techniques such as the use of CRISPR-Cas9, which allows the genome of these cells to be corrected and edited accurately, quickly, and safely to generate, for example, null phenotypes or shallow incidence blood groups. This strategy will optimize the diagnosis of erythrocyte alloimmunization.

Since the beginning of its participation in the project, Menéndez's group has published two iPSC lines from donors with rare erythrocyte phenotypes, the most difficult to achieve because of their little or no representation in our donor population. "These lines have been extensively characterized with pluripotency markers, and we have already developed the erythroid lineage differentiation method," says Paolo Petazzi, a researcher in Menéndez's group. "Finally, the in vitro differentiation of these edited iPSCs will allow us to obtain erythrocytes suitable for use in antibody identification panels."

The ID-VITRORED project is funded by the RETOS program of the Spanish Government under the reference RTC-2017-6367-1. It expects to end on December 31, 2021.