Evaluation of four chimeric Trypanosoma cruzi recombinant antigens for serological diagnosis of chronic Chagas disease in dogs: a phase II study.

BACKGROUND: Dogs are recognized as epidemiologically significant reservoirs for Trypanosoma cruzi, the causative agent of Chagas disease (CD), owing to their close association with humans and their role in sustaining the domestic and peridomestic transmission cycle. Canine seropositivity often correlates with human CD prevalence. However, the lack of commercial, high-performance diagnostic assays for canine infections remains a significant barrier to effective surveillance. Previously, our group demonstrated the diagnostic potential of four chimeric T. cruzi antigens in a phase I study, yielding results comparable to those observed in humans. The present phase II study expands upon these findings by evaluating these antigens in a larger canine cohort using indirect enzyme-linked immunosorbent assay (ELISA). The objective of this study was to assess the diagnostic performance of four chimeric recombinant T. cruzi antigens (IBMP-8.1, IBMP-8.2, IBMP-8.3, and IBMP-8.4) in immunoassays for the detection of anti-T. cruzi IgG in dogs with chronic Chagas disease.

METHODS: Immunoassays were optimized by checkerboard titration. In this phase II study, the diagnostic performance of the IBMP antigens was evaluated using 1260 canine serum samples. Cross-reactivity was assessed in an additional 752 samples from dogs with unrelated infectious diseases. The performance of the chimeric antigens was compared with a commercial human-adapted assay (Gold ELISA Chagas).

RESULTS: The Instituto de Biologia Molecular do Paraná (IBMP) antigens demonstrated area under the curve (AUC) values ranging from 89.0% to 97.4%, with diagnostic accuracy between 87.4% and 96%. IBMP-8.2 exhibited the highest sensitivity (90.3%), while IBMP-8.1, IBMP-8.3, and IBMP-8.4 achieved sensitivities of 74.8%, 72.6%, and 79.6%, respectively. The highest specificity was observed for IBMP-8.4 (99.6%), followed by IBMP-8.3 (99.0%), IBMP-8.2 (96.5%), and IBMP-8.1 (90.6%). The Gold ELISA Chagas assay showed a sensitivity of 62.3%, specificity of 98.6%, and accuracy of 89.9%. IBMP-8.2 exhibited the lowest cross-reactivity index (0.9%), closely approximating an ideal diagnostic assay.

CONCLUSIONS: The IBMP chimeric antigens demonstrated strong diagnostic performance for detecting T. cruzi infection in dogs, significantly enhancing immunoassay accuracy and minimizing diagnostic failures due to cross-reactivity. The combined use of these antigens represents a promising strategy to further improve sensitivity and specificity in future diagnostic applications.