Who benefits from cellular immune response during the Chagas disease?

We extend our previous model for the dynamical interaction between a mammal's immune response and the Trypanosoma cruzi parasite during the acute phase of Chagas disease. The model here considers both humoral and cellular responses and the different stages of T. cruzi (intracellular and extracellular phases) inside the mammal host. We analyze the dynamical time evolution of the populations obtaining phase diagrams of the model results. The steady-state solution of the system yields two outcomes associated to Healing and Chronic stationary cases, the death case obtained when just the humoral immune response alone was considered is not being present. This result implies that, surprisingly, although the immune cellular response is obviously beneficial for the host, it is also evolutionary advantageous for the parasite, as it helps to preserve the host alive and, after transmission to a healthy host, perpetuate the disease. Of course, if the cell damage by the parasite's intracellular stage is high, it may cause the host death. This possibility is accounted in the model by introducing a death criterion related to cell destruction. We present a new phase diagram, that restores the host death case and generates a phase diagram similar to the one arising from the original model.