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Clin. Vaccine Immunol. doi:10.1128/CVI.00142-08
Copyright (c) 2008, American Society for Microbiology and/or the Listed Authors/Institutions. All Rights Reserved.

DNA vaccination against Trypanosoma cruzi infection: Description of novel protective antigens expressed by amastigotes which provide immunity to highly susceptible mice

Centro Interdisciplinar de Terapia Gênica (CINTERGEN), and Departamento de Microbiologia, Imunologia e Parasitologia, Universidade Federal de São Paulo-Escola Paulista de Medicina, Rua Mirassol, 207, São Paulo-SP, Brazil, 04044-010

^* To whom correspondence should be addressed. Email: mrodrigues{at}unifesp.br.

	Abstract

Earlier studies have demonstrated protective immunity against the lethal Trypanosoma cruzi infection in highly susceptible A/Sn mice elicited by vaccination with an open reading frame (ORF) expressed by amastigotes. In our experiments, we used this mouse model to search for other amastigote-expressed ORFs with a similar property. Fourteen ORFs previously determined to be expressed in this developmental stage were individually inserted into a eukaryotic expression vector containing a nucleotide sequence that encoded a mammalian secretory signal peptide. Immunization with 13 of the 14 ORFs induced specific antibodies which recognized the amastigotes. Three of those immune sera also reacted with trypomastigotes and epimastigotes. After a lethal challenge with Y strain trypomastigotes, the vast majority of plasmid-injected mice succumbed to infection. In some cases, a significant delay in mortality was observed. Only two of these ORFs provided protective immunity against the otherwise lethal infection caused by trypomastigotes of the Y or Colombia strains. These ORFs encode members of the trans-sialidase family of surface antigens related to the previously described protective antigen Amastigote Surface Protein (ASP) 2. Nevertheless, at the level of antibody recognition, no cross-reactivity was observed between the ORFs and the previously described ASP-2 from the Y strain. In immunofluorescence analyses, we observed the presence of epitopes related to both proteins expressed by amastigotes of seven different strains. In conclusion, our approach allowed us to successfully identify two novel protective ORFs which we consider interesting for future studies on the immune response in Chagas' disease.