Dynamics and Regulatory Mechanisms of Innate Immunity and CD8 T Cells Synergy in Response to Viral Infections

In immune systems, the innate immune response and CD8 T cells play a crucial synergistic role in combating viral pathogens. In this paper, we develop a delayed viral infection model to investigate the dynamic mechanisms governing infection outcomes. The model categorizes viral infections into five states: clearance, mild, moderate, heavy, and recurrent. A key finding is that diminished innate immune responses create a bistable condition, enabling the initial antigen load and the length of the viral incubation period to act as toggle switches that determine whether infections will be mild or heavy. Furthermore, the viral incubation period induces a Hopf bifurcation, changing mild infections from a stable state to periodic oscillations, potentially leading to recurrent infections. Interestingly, enhancing the innate immune response not only bolsters the CD8 T cell-mediated destruction of infected cells but also delays the onset of the Hopf bifurcation and reduces the adverse effects of incubation periods. These insights suggest that strengthening the innate immune response and developing drugs to shorten the incubation period are viable strategies to combat viral infections.