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bioRxiv · 10.1101/2025.07.16.665074

Donor-Targeted Anti-HLA-A2 Antibody Shows Nanogram-Level Efficacy in a Novel GVHD Mouse Model

Niizuma, K.·Chang, A. H.·Kim, J. S.·Busque, S.·Majeti, R.·Nakauchi, H.·Nakauchi, Y.
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Abstract

Acute graft-versus-host disease (GVHD) remains a life-threatening complication of allogeneic hematopoietic stem cell transplantation (allo-HSCT), with limited treatment options for steroid-refractory cases. Current therapies broadly suppress immune responses, increasing infection risk and impairing graft function. We hypothesized that selective depletion of donor immune cells through HLA allele-specific targeting could offer a safer and more precise alternative. To test this, we developed a monoclonal antibody (AN7) against HLA-A2 by immunizing HLA-A24 transgenic mice with recombinant HLA-A2 tetramers, followed by hybridoma screening. AN7 specifically recognized HLA-A2 and HLA-A68, and was reformatted into murine IgG2a and human chimeric IgG1 recombinant antibodies. These retained binding specificity and mediated robust complement-dependent cytotoxicity (CDC), antibody-dependent cellular cytotoxicity (ADCC), and antibody-dependent cellular phagocytosis (ADCP) against HLA-A2+ target cells. To evaluate therapeutic potential, we established a fully MHC-mismatched allo-HSCT model using HLA-A2 transgenic donor bone marrow in lethally irradiated BALB/c recipients. A single ultra-low dose of AN7 (1-100 ng) administered post-transplant significantly improved survival and reduced GVHD while preserving donor hematopoiesis. These findings highlight the potential of allele-specific antibody-mediated clearance as a mechanistically distinct approach to donor immune modulation in GVHD.

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Niizuma, K., Chang, A. H., Kim, J. S., Busque, S., Majeti, R., Nakauchi, H., Nakauchi, Y.. 2025-07-19. Donor-Targeted Anti-HLA-A2 Antibody Shows Nanogram-Level Efficacy in a Novel GVHD Mouse Model. https://doi.org/10.1101/2025.07.16.665074

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