In this paper, a novel mathematical model of tumor–immune interaction describing the combination of Oncolytic Viruses (OVs) and Immune Checkpoint Inhibitors (ICIs) is discussed. The simple analysis of the model under several special cases is carried out. The existence and local stabilities of steady states are proved. The local Hopf bifurcation from the positive steady state is studied by considering the discrete time delay as a bifurcation parameter, both theoretically and numerically. The results show that the time delay can induce the occurrence of Hopf bifurcation, indicating that the delayed tumor-specific Cytotoxic T Lymphocyte (CTL) response induced by OVs affects the development process of tumor growth. Other factors influencing the complex dynamics of the model are also discussed. These results demonstrate that either enhancing the blockade of immune checkpoints or boosting the ability of OVs to induce anti-tumor immune responses can inhibit tumor growth. When these two factors work synergistically, the effect of inhibiting tumor growth is even more remarkable. In addition, the findings show that selecting OVs with high oncolytic potency enhances tumor control. It is hoped that this study can provide a theoretical basis for optimizing the combination therapy strategy using OVs and ICIs.
Liu et al. (Wed,) studied this question.