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Human CD55 Expression and C1 Inhibition Partially Protect Gene-Edited Pig Red Blood Cells From Human
Akihiro Maenaka1, Maho Terashita1, Kohei Kinoshita1
1Center for Transplantation Sciences, Department of Surgery, Massachusetts General Hospital/Harvard Medical School, Boston, Massachusetts, USA.
Xenotransplantation
|June 10, 2025
Summary
Gene-edited pig red blood cells (pRBCs) expressing human CD55 show reduced complement-mediated hemolysis. Combining CD55 expression with a C1-esterase inhibitor (C1-INH) further enhances protection, suggesting improved xenotransfusion survival.
Area of Science:
- Immunology
- Transplantation Biology
- Genetic Engineering
Background:
- Gene-edited pigs are explored as a source for xenotransplantation organs and potentially pig red blood cells (pRBCs).
- Human complement system poses a significant barrier to the survival of xenotransplanted cells and organs.
- Investigating methods to inhibit human complement activation on pRBCs is crucial for advancing xenotransfusion.
Purpose of the Study:
- To evaluate the in vitro efficacy of human CD55 expression on gene-edited pRBCs in inhibiting human complement.
- To assess the protective effect of a C1-esterase inhibitor (C1-INH) against complement-mediated damage to pRBCs.
- To determine the combined potential of CD55 expression and C1-INH for enhancing pRBC survival in xenotransfusion.
Main Methods:
- pRBCs were obtained from gene-edited pigs (10 gene-edits [10GE]) engineered for human complement regulatory protein expression.
- Flow cytometry was used to measure human CD46 and CD55 expression, anti-pRBC antibody binding, and C3b/iC3b deposition.
- Hemolysis assays were performed to quantify complement-dependent cytotoxicity (CDC), with and without the addition of C1-INH.
Main Results:
- Low-level expression of human CD55 was detected on 10GE pRBCs, while human CD46 was not expressed.
- 10GE pRBCs exhibited significantly reduced hemolysis (26.2% ± 3.8%) and C3b/iC3b deposition compared to TKO pRBCs (57.3% ± 2.2%).
- C1-INH administration markedly decreased hemolysis (from 18.6% ± 2.3% to 7.0% ± 1.1%) and C3b/iC3b deposition on pRBCs.
Conclusions:
- Even minimal human CD55 expression on pRBCs offers partial protection against complement-mediated hemolysis.
- C1-INH provides partial protection against hemolysis and complement component deposition, indicating its therapeutic potential.
- Enhanced human CD55 expression combined with complement inhibition strategies may be essential for successful clinical xenotransfusion of pRBCs.
