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Journal of Clinical Microbiology, November 2005, p. 5498-5503, Vol. 43, No. 11
0095-1137/05/$08.00+0 doi:10.1128/JCM.43.11.5498-5503.2005
Copyright © 2005, American Society for Microbiology. All Rights Reserved.
Instituto de Tecnología Biológica, Facultad de Bioquímica y Ciencias Biológicas, Universidad Nacional del Litoral, Santa Fe, Argentina,1 Centro de Pesquisas Aggeu Magalhães, Fundação Oswaldo Cruz, Recife,2 Departamento de Fisiologia, Instituto de Biociências, Universidade de São Paulo, São Paulo, Brazil3
Received 13 June 2005/ Returned for modification 1 August 2005/ Accepted 15 August 2005
Serological diagnosis of Trypanosoma cruzi infection is hampered by issues related to test specificity due to the cross-reactivity of most antigens with proteins of related parasites such as Leishmania spp. The recombinant calflagins are considered relevant antigens for the diagnosis of infection by Trypanosoma cruzi. In the present work, we describe two genes coding for putative calflagins in Leishmania major with the N-terminal moieties presenting high similarity with T. cruzi genes. This fact raised questions about their role in some cross-recognition of this antigen by sera from Leishmania spp.-infected individuals. The complete T. cruzi calflagin and two fragments of the protein, consisting of 146 amino acids of the N-terminal and 65 amino acids of the C-terminal regions, were expressed and evaluated against a panel of sera, which included well-characterized samples from T. cruzi, and Leishmania-infected patients. We were able to show that sera from Leishmania (Viannia) braziliensis-infected individuals recognized the recombinant full-length calflagin. Both the N-terminal and the complete protein presented the same high sensitivity (98.5% of sera from T. cruzi-infected patients was detected) but different specificities (94% and 98%, respectively, when evaluated against sera from people not infected by T. cruzi, including 15 sera from people infected with L. braziliensis). The C-terminal fragment presented low sensitivity (70%) but 100% specificity. We propose the use of these antigens in two sequential assays to optimize the serological diagnosis of T. cruzi infection in humans in geographic areas where Leishmania spp. infection is coendemic.
C.R. and G.C. contributed equally to this work.
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