NK Cell Tumor Therapy Modulated by UV-Inactivated Oncolytic Herpes Simplex Virus Type 2 and Checkpoint Inhibitors

Abstract

Background: Oncolytic virotherapy is a new and safe therapeutic strategy for cancer treatment. In our previous study, a new type of oncolytic herpes simplex virus type 2 (oHSV2) was constructed. Following the completion of a preclinical study, oHSV2 has now entered into clinical trials for the treatment of melanoma and other solid tumors (NCT03866525). Oncolytic viruses (OVs) are generally able to directly destroy tumor cells and stimulate the immune system to fight tumors. Natural killer (NK) cells are important components of the innate immune system and critical players against tumor cells. But the detailed interactions between oncolytic viruses and NK cells and these interaction effects on the antitumor immune response remain to be elucidated. In particular, the functions of activating surface receptors and checkpoint inhibitors on oHSV2-treated NK cells and tumor cells are still unknown. Methods: UV-inactivated oncolytic herpes simplex virus type 2 (UV-oHSV2) was used to stimulate immune cells (especially NK cells), and the NK cell-induced antitumor effects and their mechanisms were further investigated. In addition, the effect of UV-oHSV2 stimulation with or without checkpoint (NKG2A/HLA-E) antibody treatment on NK cell antitumor activity was explored in vitro and in vivo. Findings: We found that UV-oHSV2 potently activates human peripheral blood mononuclear cells, leading to increased antitumor activity in vitro and in vivo. Further investigation indicated that UV-oHSV2-stimulated NK cells release IFN-γ via Toll-like receptor 2 (TLR2)/NF-κB signaling pathway and exert antitumor activity via TLR2. We found for the first time that the expression of a pair of checkpoint molecules, NKG2A (on NK cells) and HLA-E (on tumor cells), is upregulated by UV-oHSV2 stimulation. Anti-NKG2A and anti-HLA-E treatment could further enhance the antitumor effects of UV-oHSV2-stimulated NK92 cells in vitro and in vivo. Interpretation: Our results indicate that UV-oHSV2-stimulated NK cells have enhanced antitumor activity. The activating surface receptor (TLR2), checkpoint inhibitor (NKG2A) on NK cells and checkpoint inhibitor (HLA-E) on tumor cells were relative to UV-oHSV2-stimulated NK cells antitumor effects. Funding: National Major Scientific and Technological Special Project for “Significant New Drugs Development” (2018ZX09733002). Declaration of Interests: Z. Fang is employed by Wuhan Binhui Biopharmaceutical Co., Ltd. He would like to state clearly that there are no commercial conflicts with this work. There are no patents, products in development or marketed products to declare. The interpretation of the results was completely independent from any company's opinion. This affiliation does not alter the authors’ adherence to all policies on sharing data and materials. The authors declare no potential conflict of interest. Ethics Approval Statement: Peripheral blood from healthy donors and lymphocytes from patient pleural effusion were collected according to the protocols (2018-059-007) approved by the Ethics Committee of the Hubei Cancer hospital. All animal experiments were conducted under protocol approved by the Hubei Province, PR China, Biological Studies Animal Care and Use Committee (HBUT No. 2018010).