Spatiotemporal Dynamics of an HIV Infection Model with Delay in Immune Response Activation

Abstract

We propose and analyse an human immunodeficiency virus (HIV) infection model with spatial diffusion and delay in the immune response activation. In the proposed model, the immune response is presented by the cytotoxic T lymphocytes (CTL) cells. We first prove that the model is well-posed by showing the global existence, positivity, and boundedness of solutions. The model has three equilibria, namely, the free-infection equilibrium, the immune-free infection equilibrium, and the chronic infection equilibrium. The global stability of the first two equilibria is fully characterized by two threshold parameters that are the basic reproduction number $R_{\mathrm{0}}$ and the CTL immune response reproduction number $R_{\mathrm{1}}$. The stability of the last equilibrium depends on $R_{\mathrm{0}}$ and $R_{\mathrm{1}}$ as well as time delay $\mathrm{\tau }$ in the CTL activation. We prove that the chronic infection equilibrium is locally asymptotically stable when the time delay is sufficiently small, while it loses its stability and a Hopf bifurcation occurs when $\mathrm{\tau }$ passes through a certain critical value.