Comparative evaluation of immunoassays to improve access to diagnosis for Chagas disease in Colombia.

OBJECTIVE: Chagas disease affects over six million people, but less than 1% are diagnosed and treated. Complicated diagnostic processes are a major barrier. Colombia's previous diagnostic algorithm, using in-house tests, was difficult to scale up, creating significant access barriers for patients. A new algorithm using commercially manufactured immunoassays would potentially improve access, but these tests' performance in Colombian patients with Chagas disease is not well known. METHODS: We assessed seven commercially available assays. Samples (n=501), 93.8% originating from Colombia, were characterized as positive or negative based on standard procedure at the National Reference Laboratory. Performance characteristics were calculated for individual assays and hypothetical test pairings, then compared to the existing algorithm. RESULTS: Five of seven assays exhibited sensitivity >98% while six showed specificity >97%. A total antigen ELISA paired with a recombinant assay provided similar performance to the current diagnostic process. Six of six assays tested proved capable of detecting different Trypanosoma cruzi genetic lineages. CONCLUSIONS: The study indicated that several commercial assays accurately detect T. cruzi infection in Colombian patients. A simplified testing process with two commercial assays could perform comparably to the previous process, reducing cost and accessibility barriers and facilitating national scale-up.

Low frequency of circulating CD8+ T stem cell memory cells in chronic chagasic patients with severe forms of the disease.

BACKGROUND: CD8+ T cells have been shown to play a crucial role in Trypanosoma cruzi infection. Memory CD8+ T cells can be categorised based on their distinct differentiation stages and functional activities as follows: stem cell memory (TSCM), central memory (TCM), transitional memory (TTM), effector memory (TEM) and terminal effector (TTE) cells. Currently, the immune mechanisms that control T. cruzi in the chronic phase of the infection are unknown. METHODOLOGY/PRINCIPAL FINDINGS: To characterise the CD8+ T cell subsets that could be participating in the control of T. cruzi infection, in this study, we compared total and T. cruzi-specific circulating CD8+ T cells with distinctive phenotypic and functional features in chronic chagasic patients (CCPs) with different degrees of cardiac dysfunction. We observed a decreased frequency of total TSCM along with an increased frequency of TTE in CCPs with severe disease. Antigen-specific TSCM cells were not detectable in CCPs with severe forms of the disease. A functional profile of CD8+ T cell subsets among CCPs revealed a high frequency of monofunctional CD8+ T cells in the most severe patients with IFN-γ+- or TNF-α+-producing cells. CONCLUSIONS/SIGNIFICANCE: These findings suggest that CD8+ TSCM cells may be associated with the immune response to T. cruzi and outcome of Chagas disease, given that these cells may be involved in repopulating the T cell pool that controls infection.