title: Resistance of Trypanosoma cruzi to blood clearance induced by acute-phase immune mouse serum.
abstract: To investigate functional changes in Trypanosoma cruzi parasites induced during their interaction with the vertebrate host, we compared the blood clearance profiles of blood forms isolated from infected normal mice (Reg-Tc) or from infected mice immunodepressed after treatment with cyclophosphamide (Cy-Tc). Parasite blood numbers were measured at various time intervals in animals injected intravenously (i.v.) with 1-2 x 10(6) T. cruzi of either isolate. In the absence of added immune sera (spontaneous clearance), Reg-Tc and Cy-Tc were cleared from blood at similar rates. However, when acute immune mouse serum (Ac-IMS) was injected i.v. 2 min after inoculation of parasites, a significant proportion of Cy-Tc only was cleared from the blood an hour later, whereas Reg-Tc were not, their clearance profile being identical to that observed in mice injected with normal mouse serum. Cy-Tc susceptibility to Ac-IMS was not the result of a toxic effect of cyclophosphamide over T. cruzi as parasites recovered from animals immunodepressed by irradiation before infection were cleared similarly by acute serum. Contrary to Ac-IMS, chronic immune mouse serum induced similar rates of disappearance of Reg-Tc and Cy-Tc from blood. Our results suggest the occurrence of T. cruzi selection or modification during the acute phase, which leads to an increased parasite resistance to the clearance properties of acute-phase antibodies.
authors: Departamento de Imunologia, Universidade de São Paulo, Brazil.
authors: J M
authors: JM
authors: Alvarez
authors: C R
authors: CR
authors: Marinho
authors: A
authors: A
authors: Oshima
authors: L
authors: L
authors: Guimaraes
authors: H
authors: H
authors: Menezes
mesh_terms: D000210:Acute-Phase Reaction / Q000097:blood / Q000276:immunology*; D000704:Analysis of Variance; D000818:Animals; D014355:Chagas Disease / Q000097:blood / Q000276:immunology*; D003520:Cyclophosphamide; D005260:Female; D007106:Immune Sera / Q000276:immunology*; D007165:Immunosuppression Therapy; D051379:Mice; D014349:Trypanosoma cruzi / Q000276:immunology*
chemical_list: D007106:Immune Sera; D003520:Cyclophosphamide