Rat Models to Investigate Host Macrophage Defense against <i>Trypanosoma cruzi</i>

Trypanosoma cruzi is the causal agent of Chagas' disease, an infection with a great impact on public health in Latin America. One of the challenges to understand Chagas' disease lies on the complex host-parasite interaction. The understanding of this interaction requires the use of appropriate experimental models that mimic the human disease. Here, we have used two lineages of rats (Wistar and Holtzman) to comparatively evaluate the course of the acute infection (Y strain). Infection was monitored by parasitemia, cardiac and skeletal muscle parasitism and inflammation, heart ultrastructure, recruitment of monocytes/macrophages and nitric oxide, and arginase production by these cells. Although both rats were able to infect, only Holtzman rats developed a marked infection in the cardiac and skeletal muscles, in parallel to a high recruitment of first-line defense cells. A high number of inflammatory macrophages directed parasite clearance. By the end of the acute phase, Holtzman rats showed consistent disease control. Interestingly, parasite killing was not related to nitric oxide production likely inhibited by an arginase-dependent mechanism. Our work demonstrates differential responses of Holtzman and Wistar rats to T. cruzi, and highlights the use of Holtzman rats as useful models for further studies of cardiac/skeletal muscle tropism and innate immune responses that protect the host against parasite replication. This is important for the development of proper therapeutic interventions.