Modelling HIV-TB co-infection dynamics in the presence of immunosenescence and treatment

An individual's age at infection with HIV-1 influences progression of the diseaseand the immune system's regenerative capacity . Using ordinary differential equations,we firstly consider a simple HIV-1 model describing the immunological changes inthe concentration of the CD4⁺ T cells, HIV-1 virions, macrophages and the stemcellreservoir. We assess the dynamics of HIV-1 infection and the rapid exhaustionof the T-cell reservoir with respect to immunosenescence. Secondly, we incorporateTuberculosis (TB) infection and highly active anti-retroviral therapy into the simpleHIV-1 model. Numerical simulations are carried out to demonstrate the effects of TBand HIV-1 on the dynamics of the stem cell reservoir. Analysis of early treatment andlate treatment reveals that the former renders a longer survival period than the latter.Evaluation of treatment interruption suggests viral and bacterial rebounds, and a rapiddecline of immune resources, thus shortening the patient's life span.