This Article Full Text Full Text (PDF) Other Versions of this Article: CVI.00401-06v1 14/4/355    most recent Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Reprints and Permissions Copyright Information Books from ASM Press MicrobeWorld Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Cheng, K. Y. Articles by Shah, D. O. Search for Related Content PubMed PubMed Citation Articles by Cheng, K. Y. Articles by Shah, D. O.

 Previous Article  |  Next Article 

Clinical and Vaccine Immunology, April 2007, p. 355-361, Vol. 14, No. 4
1071-412X/07/$08.00+0     doi:10.1128/CVI.00401-06
Copyright © 2007, American Society for Microbiology. All Rights Reserved.

Immunoblot Assay Using Recombinant Antigens as a Supplemental Test To Confirm the Presence of Antibodies to Trypanosoma cruzi

Emerging Pathogens and Infectious Diseases R&D, Abbott Diagnostics Division, Abbott Laboratories, Abbott Park, Illinois,¹ Departments of Internal Medicine and Epidemiology, University of Iowa, Iowa City, Iowa,² Transmissible Diseases Department, American Red Cross, Rockville, Maryland,³ Medical Service, Department of Veterans Affairs Medical Center, Iowa City, Iowa⁴

Received 19 October 2006/ Returned for modification 4 January 2007/ Accepted 26 January 2007

The diagnosis of chronic Chagas' disease is generally made by detecting antibodies to Trypanosoma cruzi. Most conventional serological tests are based on lysates of whole parasites or semipurified antigen fractions from T. cruzi epimastigotes grown in culture. The occurrence of inconclusive and false-positive results has been a persistent problem with the conventional assays, and there is no universally accepted gold standard for confirmation of positive test results. We describe here an immunoblot assay for detecting antibodies to T. cruzi in which four chimeric recombinant antigens (rAgs), designated FP3, FP6, FP10, and TcF, are used as target antigens. Each of these rAgs is composed of several antigenically distinct regions and includes repetitive as well as nonrepetitive sequences. Each rAg is coated as a discrete line on a nitrocellulose strip. Assay sensitivity was assessed by testing 345 specimens known to be positive for antibodies to T. cruzi. All 345 of these samples showed two to four reactive test bands in addition to the three on-board control bands that are on each strip. Assay specificity was determined by testing 500 specimens from random U.S. blood donors, all of which gave negative results. Based on the results obtained in this study, we propose the following scheme for interpretation of test results: (i) no bands or a single test band = a negative result; (ii) two or more test bands with at least one band showing intensity of 1+ or higher = a positive result; and (iii) multiple faint test bands (±) = indeterminate result. Based on this scheme, the prototype immunoblot assay showed sensitivity of 100% (n = 345) and specificity of 100% (n = 500). Additionally, all 269 potentially cross-reacting and T. cruzi antibody-negative specimens tested negative in our immunoblot assay. The rAg-based immunoblot assay has potential as a supplemental test for confirming the presence of antibodies to T. cruzi in blood specimens and for identifying false-positive results obtained with other assays.

Published ahead of print on 7 February 2007.