Objective: Xenotransfusion using genetically engineered (GE) pig red blood cells (pRBCs) offers a potential solution to blood shortages, particularly in emergencies. This study aimed to evaluate the suitability of brain-dead human subjects as a preclinical model for xenotransfusion by comparing their hematological and immunological profiles with those of acute blood loss (ABL) patients and assessing the feasibility, safety, and immunological responses to GE pRBCs in a brain-dead human subject.
Methods: Comprehensive evaluations were conducted on hematological, biochemical, electrolyte, coagulation, and inflammatory markers, arterial blood gas parameters, and immunological profiles in brain-dead subjects (n=179) and ABL patients (n=104) requiring transfusion. In vitro assessments of anti-triple-knockout (TKO; lacking Gal, Neu5Gc, and Sda antigens) pig RBC responses were also performed in brain-dead subjects (n=31) and compared to those of ABL patients (n=102).
RBCs from TKO pigs expressing human CD55 (housed under pathogen-free conditions) were labeled with CFSE for tracking. A single brain-dead human subject received a transfusion of GE pRBCs, with pre-transfusion treatments including an anti-C5 inhibitor, corticosteroids, and antihistamines. Monitoring included continuous vital sign tracking, hematological and immunological assessments, complement activation assays, and pathogen screening.
Results: Comparative analysis revealed similar pathophysiological and immunological profiles between DBD and ABL patients, supporting the former’s relevance as a xenotransfusion model.
GE pRBCs exhibited survival rates of 50% at 24 hours, 15% at 48 hours, and were cleared by 72 hours. Pre-transfusion anti-pig IgM levels were low, transiently decreased post-transfusion, and rebounded by day 3. Anti-pig IgG levels, initially undetectable, significantly increased by day 7, accompanied by heightened complement-dependent cytotoxicity and hemagglutination. Both classical and alternative complement pathways were activated but moderated by regulatory mechanisms. No pig-derived pathogens were detected.


Conclusion: Brain-dead human subjects closely replicate the clinical conditions of ABL, providing a valuable preclinical model for xenotransfusion research, particularly in settings where nonhuman primate models have limitations. This study establishes the feasibility and safety of GE pRBC xenotransfusion, offering critical insights into immune responses and pathogen safety. The absence of zoonotic transmission and the manageable immune profile observed in this first-in-human trial underscore the potential of xenotransfusion as a promising solution to global blood shortages in critical care.