Validation of Trypanosoma cruzi-GPI Anchored Membrane Proteins for Specific Sero-Diagnosis of Chagas Disease

Trypanosoma cruzi-GPI anchored membrane proteins (T. cruzi-GPI-AMP) were isolated, purified, characterized and antigenically validated to be proposed as candidates to serologically diagnose Chagas disease. The partition Triton-114 protein fractioning method allowed recovering nearly 7% T. cruzi-GPI-AMP from the total parasite proteins. The immunogenic capability of T. cruzi-GPI-AMP was demonstrated in experimental hosts. Validation of T. cruzi-GPI-AMP, as an antigenic product to make up an alternative test for serologic diagnosis of Chagas disease, was performed in 174 sera samples: 112 from unquestionable chagasic patients and 62 from non-chagasic to estimate its sensitivity and specificity, respectively. Statistical analysis revealed 100% sensitivity, specificity, positive and negative predictive values, with P<0.005. In addition, estimation of the Kappa index revealed 100% agreement, indicating a perfect concordance between the T. cruzi-GPI-AMP test and the condition of the chagasic patients following clinical, parasitological and serological criteria. Separation by electroelution revealed the presence of several T. cruzi-GPI-AMP fractions, ranging from 23 to 123 kDa, specifically recognized by anti-T. cruzi antibodies contained in sera from acute and chronic chagasic patients. These results lead us to conclude that T. cruzi-GPI-AMP antigen is an alternative diagnostic test sensitive and specific enough to warrant a reliable sero-diagnosis of Chagas disease.