Acta Tropica 103 (2007) 14–25 Distribution of Trypanosoma cruzi stage-specific epitopes in cardiac muscle of Calomys callosus, BALB/c mice, and cultured cells infected with different infective forms Noemi N. Taniwaki a , Claudio Vieira da Silva b , Solange da Silva b , Renato A. Mortara b,∗ a Se¸ c˜ ao de Microscopia Eletrˆ onica do Instituto Adolfo Lutz, Av. Dr. Arnaldo 355, 01246-902 SP, Brazil b Departamento de Microbiologia, Imunologia e Parasitologia, UNIFESP - Escola Paulista de Medicina, Rua Botucatu, 862 6 o andar, 04023-062 S˜ ao Paulo, SP, Brazil Received 6 March 2007; received in revised form 4 May 2007; accepted 14 May 2007 Available online 18 May 2007 Abstract To examine whether distinct parasite infective forms or the mammalian host could affect the distribution of Trypanosoma cruzi stage-specific epitopes defined by monoclonal antibodies (Mabs) raised against mammalian-stage parasite forms, immunofluores- cence studies followed the intracellular life cycle of the parasite in the cardiac muscle of Calomys callosus and BALB/c mice in the acute phase of the disease and in LLC-MK 2 cultured cells. Animals and cells were infected either with tissue-culture derived trypomastigotes (TCT) or bloodstream trypomastigotes (BT) from the Y strain of T. cruzi. Samples were examined under confocal fluorescence microscopy after labeling with Mabs 2C2, 1D9, 2B7, 3G8, 3B9, and 4B9 that react with carbohydrate epitopes on Ssp-4, a major amastigote surface glycoprotein; Mab 4B5 that identifies a noncarbohydrate epitope on all intracellular parasites stages, and Mab 3B2 that also recognizes a noncarbohydrate epitope expressed only in flagellated forms. Samples were double labeled with DAPI to visualize parasites’ kinetoplasts and nuclei. Most of the Mabs used in this work displayed a surface labeling pattern on amastigotes present in Calomys and mice hearts, and in LLC-MK 2 cultured cells infected with BT or TCT. Mab 2B7, however, displayed a marked polymorphic distribution in antigen expression between both mammalian hosts, independent on the infective form. Beyond the polymorphic distribution of amastigote surface epitopes, Calomys, and mice heart sections presented several inflammatory cells around amastigotes and trypomastigotes nests. © 2007 Elsevier B.V. All rights reserved. Keywords: Trypanosoma cruzi; Amastigote; Arypomastigote; Monoclonal antibody; Epitope; Confocal microscopy ∗ Corresponding author. Disciplina de Parasitologia, Departamento de Microbiologia, Imunologia e Parasitologia, UNIFESP - Escola Paulista de Medicina, Rua Botucatu, 862 6 o andar, 04023-062 S˜ ao Paulo, SP, Brazil. Tel.: +55 11 5579 8306; fax: +55 11 5571 1095. E-mail address: renato@ecb.epm.br (R.A. Mortara). 1. Introduction Trypanosoma cruzi is the causative agent of Cha- gas’ disease, an important endemic parasitosis that affects some 13 million of people in Latin America (http://www.who.int/tdr/dw/chagas2003.htm). The par- asite’s life cycle alternates between vertebrates and insects, comprised of several distinct developmental stages in both the reduviid insect vector and the 0001-706X/$ – see front matter © 2007 Elsevier B.V. All rights reserved. doi:10.1016/j.actatropica.2007.05.007