Body: Serum from patients with previous transplants, transfusion, and pregnancies may contain multiple HLA-specific antibodies recognizing various functional epitopes or eplets. For these patients, current PRA calculation leads to low transplant probability. Eplet-based PRA calculation allows for increased transplantation probability and eplet matching with donors allows for improved transplantation outcomes and reduced immunosuppression dosage. Identifying DSA eplets in these cases holds clinical significance, with tools like HLAMatchmaker and adsorption and elution with crossmatch cells (AXE) developed for this purpose. In a case study, in conjunction with the above tools, MagSort beads targeting A*01:01, A*02:01, A*68:01, B*13:01, B*44:02, B*57:01, C*01:02, C*02:02, C*04:01, and C*05:01 were used to isolate DSAs from high PRA patient serum. LABScreen assays was performed on the serum and the isolated DSAs. HLAMatchmaker analysis of the pre-treatment serum binding pattern identified 33 potential eplets. MagSort DSA isolations narrowed down these possibilities. A*02:01, A*68:01, and B*57:01 beads confirmed 62GE and 144TKH eplets, while C*02:02, C*04:01, and C*05:01 beads confirmed 80K eplet, and B*13:01 and B*44:02 beads confirmed 80TLR and 45KE eplets. A*01:01 beads showed a binding pattern toward B*15:12, B*44:02, B*44:03, B*45:01, B*50:02, and B*82:01. Multiple sequence alignments identified putative 163R/L 167G/S eplet consistent with reports describing this same reactivity pattern. The isolated A*01:01-specific DSA binding pattern was confirmed with AXE using recombinant cells expressing A*01:01, and EBV-immortalized human cells were utilized for adsorption and elution.
Conclusion: In this case study, employing various tools has led us to narrow down the DSA eplet possibilities to five potential eplets. This selection of possible eplets may allow for higher transplant probability using eplet-based PRA calculations. This binding pattern suggests that there are additional eplets to be identified. To validate this novel putative eplet further, ongoing investigations into A*01:01 mutations are underway.
