Enzymatic Conversion of Human Blood Group a Kidneys to Universal Blood Group O

Abstract Introduction The ABO blood group restriction on allocation of donor organs leads to waiting time disadvantages for individuals of more restrictive blood types. Here, we outline the first preclinical use of two enzymes from Flavonifractor plautii to convert human blood group A kidneys to universal blood group O. Methods Six pairs of human kidneys rejected for transplantation and offered for research were used to in this study with approval from the National Research Ethics committee and Research and Development Office (NRES: 15/NE/0408). Three pairs were perfused for 6 h using normothermic machine perfusion (NMP), and three pairs were perfused for 24 h using hypothermic machine perfusion (HMP), with one kidney per pair randomised to enzyme treatment. Cortical biopsies collected throughout perfusion were examined for antigen loss using immunofluorescence microscopy. Results After 2hrs of NMP, a significant loss of 83.4±10.2% blood group A antigen expression was observed compared to pre-treatment levels (p=0.012), while no significant changes were observed in control kidneys (p=0.999). For HMP, a maximal loss of 71.2±21.9% was observed after 6 h (p=0.066), with no decrease observed in the contralateral controls (p=0.977). Haemodynamic perfusion parameters were stable in both cohorts, with no significant difference between control vs treated kidneys. Conclusion Our results show a loss of 70-80% of blood group A antigens in as little as 2 h of NMP and 6 h of HMP. These approaches pave the way for the first clinical studies that could herald the start of a new era that transforms donor organ allocation in kidney transplantation.