ABO gene editing for the conversion of blood type A to universal type O in Rhnull donor-derived human-induced pluripotent stem cells.

The limited availability of red cells with extremely rare blood group phenotypes is one of the global challenges in transfusion medicine that has prompted the search for alternative self-renewable pluripotent cell sources for the in vitro generation of red cells with rare blood group types. One such phenotype is the Rhnull , which lacks all the Rh antigens on the red cell membrane and represents one of the rarest blood types in the world with only a few active blood donors available worldwide. Rhnull red cells are critical for the transfusion of immunized patients carrying the same phenotype, besides its utility in the diagnosis of Rh alloimmunization when a high-prevalence Rh specificity is suspected in a patient or a pregnant woman. In both scenarios, the potential use of human-induced pluripotent stem cell (hiPSC)-derived Rhnull red cells is also dependent on ABO compatibility. Here, we present a CRISPR/Cas9-mediated ABO gene edition strategy for the conversion of blood type A to universal type O, which we have applied to an Rhnull donor-derived hiPSC line, originally carrying blood group A. This work provides a paradigmatic example of an approach potentially applicable to other hiPSC lines derived from rare blood donors not carrying blood type O.

Impact of ABO incompatibility on allogeneic peripheral blood progenitor cell transplantation after reduced intensity conditioning.

BACKGROUND: Most studies indicate that ABO incompatibility has no effect on the clinical outcome after allogeneic peripheral blood progenitor cell (PBPC) transplantation (allo-PBPCT). However, it carries additional risks of hemolytic reactions, delayed red blood cell (RBC) engraftment, and pure red cell aplasia (PRCA). Data on these events after reduced intensity conditioning (RIC) regimens are limited, but recent studies have suggested a higher transplant-related mortality (TRM) and morbidity in this setting. STUDY DESIGN AND METHODS: We investigated the impact of ABO-matching on the outcome of 77 patients included in a prospective RIC allo-PBPCT protocol, focusing on engraftment, transfusion requirements, graft-versus-host disease, TRM, and survival. RESULTS: There were 17 (22%) minor and 8 (10%) major ABO-incompatible transplants. No graft failures were observed. After major ABO-incompatible grafts, RBC engraftment was delayed, longer thrombocytopenia periods were documented, and transfusion requirements increased. A transient mild hemolysis occurred in 10 patients, 7 (41%) minor and 3 (37%) major ABO-mismatched. A PRCA was observed in a O+ patient with a pretransplant anti-Jka, grafted from an A + Jka+ donor. Graft-versus-host disease, disease progression, and TRM were not affected by ABO matching. CONCLUSION: ABO incompatibility was not associated with clinically relevant hemolysis after the RIC protocol used and did not impair the clinical outcome. PRCA was only observed in one patient, with a non-ABO RBC allo-antibody.