A novel form of immunotherapy using antigen peptides conjugated on PD-L1 antibody.

Immune checkpoint inhibitors (ICIs), including programmed cell death protein 1 (PD-1)/programmed death-ligand 1 (PD-L1) and cytotoxic T-lymphocyte-associated protein 4 have shown promising cancer clinical outcomes. However, IC therapy has low patient response rates (10%-15%). Thus, ICIs and sufficient antigen combinations into the tumor microenvironment (TME) is important to produce strong tumor-specific adaptive immune responses. Mice were treated with cisplatin, and human cancer cells were exposed to inflammatory cytokines, to confirm increased PD-L1 and major histocompatibility complex (MHC) I expression by tumor cells or dendritic cells. TC-1, CT26, B16-F1, or B16-F10 tumor cells, and bone marrow-derived dendritic cells, were treated with interferon (IFN)-β, IFN-γ, or tumor necrosis factor-α to identify the molecular mechanisms underlying tumor PD-L1 and MHC I upregulation, and to examine MHC I, CD40, CD80, CD86, or PD-L1 levels, respectively. For synergistic combination therapy, αPD-L1 monoclonal antibody (mAb) covalently linked to the long E7 peptide was generated. Chemotherapy shifted the TME to express high PD-L1 and MHC I, resulting in targeted ICI cargo delivery and enhanced generation and activation of tumor antigen-specific T cells. Synergistic effects of vaccination and IC blockade in the TME were demonstrated using an anti-PD-L1 mAb covalently conjugated to the E7 long peptide.