Delay differential model for tumourimmune dynamics with HIV infection of CD4+ T-cells

In this paper, we introduce ordinary and delay differential equations to describe the interactions between a malignant tumour and the immune system in vivo in the presence of human immunodeficiency virus (HIV) infection of CD4(+) T-cells. In the delay model, we take into account the time lags required by the healthy effector cell components to recognize the pathogens and tumour cells. The models consist of four populations: tumour cells, healthy effector cells (CD4(+) T-cells), effector cells infected by HIVs and free viral particles. The presence of delay term in the model leads to a notable increase in the complexity of the observed behaviour. We investigate the qualitative behaviour of the models and find the conditions that guarantee the asymptotic stability of the steady states. Numerical simulations are provided to illustrate and extend the theoretical results. The obtained results are consistent with the real phenomena and give a better understanding of cancer immunity and viral oncogenesis.