Establishment of Anti-Dog Programmed Cell Death Ligand 1 Monoclonal Antibodies for Immunohistochemistry.

Abstract

Immune checkpoint blockade therapy has shown successful clinical outcomes in multiple human cancers. In dogs, several types of tumors resemble human tumors in many respects. Therefore, several groups have developed the anti-dog programmed cell death ligand 1 (dPD-L1) monoclonal antibodies (mAbs) and showed efficacy in several canine tumors. To examine the abundance of dPD-L1 in canine tumors, anti-dPD-L1 diagnostic mAbs for immunohistochemistry are required. In this study, we immunized the peptide in the dPD-L1 intracellular domain, and established anti-dPD-L1 mAbs, L₁Mab-352 (mouse IgG₁, kappa), and L₁Mab-354 (mouse IgG₁, kappa). In enzyme-linked immunosorbent assay, L₁Mab-352 and L₁Mab-354 showed high-binding affinity to the dPD-L1 peptide, and the dissociation constants (K_D) were determined as 6.9 × 10^-10 M and 7.2 × 10^-10 M, respectively. Furthermore, L₁Mab-352 and L₁Mab-354 were applicable for the detection of dPD-L1 in immunohistochemical analysis in paraffin-embedded dPD-L1-overexpressed cells. These results indicated that L₁Mab-352 and L₁Mab-354 are useful for detecting dPD-L1 in immunohistochemical analysis.