Abstract
Cancer is the most acute disease and the leading cause of patient death worldwide. Both chemotherapy and molecular-based therapies play an important role in curing cancer. However, the median and overall survival of patients is poor. To date, immune therapies have changed the treatment methods for cancer patients. Programmed death ligand 1 (PD-L1, also known as B-H1, CD274) is a well-studied tumor antigen. PD-L1 is overexpressed in colon cancer, lung cancer, and so on and plays a vital role in cancer development. In this study, anti-PD-L1 single-domain antibodies were identified from recombinant human PD-L1 (rhPD-L1)-immunized llamas. Then, we generated a novel multifunctional anti-PD-L1-CD16a-IL15 antibody targeting PD-L1-positive tumor cells. Anti-PD-L1-CD16a-IL15 was constructed by linking the Interleukin-2 (IL-2) signal peptide, anti-PD-L1 single domain antibody (anti-PD-L1-VHH) and anti-cluster of differentiation 16a single domain antibody (anti-CD16a-VHH), and Interleukin-15/Interleukin-15 receptor alpha (IL15/IL-15Rα). This anti-PD-L1-CD16a-IL15 fusion protein can be expressed and purified from HEK-293F cells. In vitro, our data showed that the anti-PD-L1-CD16a-IL15 fusion protein can recruit T cells and drive natural killer cells (NK) with specific killing of PD-L1-overexpressing tumor cells. Furthermore, in the xenograft model, the anti-PD-L1-CD16a-IL15 fusion protein inhibited tumor growth with human peripheral blood mononuclear cells (PBMCs). These data suggested that the anti-PD-L1-CD16a-IL15 fusion protein has a latent function in antitumour activity, with better guidance for future cancer immunotherapy.