A MODEL FOR TREATMENT STRATEGY IN THE CHEMOTHERAPY OF AIDS

Mathematical models are developed for the chemotherapy of AIDS. The mo dels are systems of differential equations describing the interaction of the HIV infected immune system with AZT chemotherapy. The models pr oduce the three types of qualitative clinical behavior: an uninfected steady state, an infected steady state (latency) and a progression to RIDS state. The effect of treatment is to perturb the system from prog ression to AIDS back to latency. Simulation of treatment schedules is provided for the consideration of treatment regimes. The following iss ues of chemotherapy are addressed: (i) daily frequency of treatment, ( ii) early versus late initiation of treatment and (iii) intermittent t reatment with intervals of no treatment. The simulations suggest the f ollowing properties of AZT chemotherapy: (i) the daily period of treat ment does not affect the outcome of the treatment, (ii) treatment shou ld not begin until after the final decline of T cells begins (not unti l the T cell population falls below approximately 300 mm(-3)) and then , it should be administered immediately and (iii) a possible strategy for treatment which may cope with side effects and/or resistance, is t o treat intermittently with chemotherapy followed by interruptions in the treatment during which either a different drug or no treatment is administered. These properties are revealed in the simulations, as the model equations incorporate AZT chemotherapy as a weakly effective tr eatment process; We incorporate into the model the fact that AZT treat ment does not eliminate HIV, but only restrains its progress. The math ematical model, although greatly simplified as a description of an ext remely complex process, offers a means to pose hypotheses concerning t reatment protocols, simulate alternative strategies and guide the qual itative understanding of AIDS chemotherapy.