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Clinical and Vaccine Immunology, August 2008, p. 1292-1300, Vol. 15, No. 8
1071-412X/08/$08.00+0 doi:10.1128/CVI.00142-08
Copyright © 2008, American Society for Microbiology. All Rights Reserved.

Centro Interdisciplinar de Terapia Gênica,1 Departamento de Microbiologia, Imunologia e Parasitologia, Universidade Federal de São Paulo-Escola Paulista de Medicina, Rua Mirassol, 207, São Paulo, Brazil 04044-0102
Received 24 April 2008/ Returned for modification 10 June 2008/ Accepted 16 June 2008
Earlier studies have demonstrated in A/Sn mice highly susceptible to Chagas' disease protective immunity against lethal Trypanosoma cruzi infection 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 strain. These ORFs encode members of the trans-sialidase family of surface antigens related to the previously described protective antigen amastigote surface protein 2 (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 to Chagas' disease.
Published ahead of print on 25 June 2008.
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