Development and Characterization of Novel Monoclonal Antibodies Against Human DNAM-1

DNAM-1 (CD226) is an activating immunoreceptor expressed on lymphocytes and myeloid cells. CD155 and CD112 are the ligands for DNAM-1. DNAM-1 plays an important role in tumor immunity mediated by CD8⁺ T cells and NK cells. Moreover, the interaction of DNAM-1 with the ligands contributed to the development of acute graft versus host disease (GVHD) and treatment with anti-DNAM-1 monoclonal antibodies (mAb) dramatically improved acute GVHD in a mouse model, suggesting that DNAM-1 may be a good molecular target for therapy to acute GVHD in human. In this study, we generated and characterized five novel clones of anti-human DNAM-1 mAbs, named TX94, TX95, TX96, TX107, and TX108. Among these mAbs, TX94 is a unique neutralizing mAb that most efficiently blocked the interaction between DNAM-1 and CD155. Furthermore, TX94 inhibited NK cell-mediated cytotoxicity against a tumor cell line and suppressed CD8⁺ T cell proliferation mediated by allogeneic mixed lymphocyte reaction. Thus, TX94 may be useful for molecular therapy targeting DNAM-1.