Resistance in oncolytic viral therapy for solid tumors

Therapeutic resistance poses a significant obstacle in cancer control, and oncolytic viral therapy also faces the challenge of virus resistance. In this study, we propose models based on ordinary and delay differential equations to investigate the impact of resistance on tumor -virus interactions. The tumor cells are categorized as sensitive, resistant, or infected by oncolytic viruses. We show that if resistant tumor cells cannot be transformed into sensitive cells, every tumor cell will eventually acquire resistance. The model can possess at most one positive equilibrium, and we determine the critical delay magnitude beyond which the equilibrium becomes unstable. Our numerical simulations indicate that delays in the viral cycle can result in an increase in the total tumor burden. However, in terms of the overall tumor load, resistance may not be detrimental to the host if the delay in the viral cycle is substantial.