Lateral flow immunoassay for diagnosis of Trypanosoma cruzi infection with high correlation to the radioimmunoprecipitation assay.

The incidence of blood donors seropositive for Trypanosoma cruzi in North America has increased with population migration and more rigorous surveillance. The United States, considered nonendemic for T. cruzi, could therefore be at risk to exposure to parasite transmission through blood or organ donations. Current tests show variable reactivity, especially with Central American sera. Here we describe the development of a lateral flow immunoassay for the rapid detection of T. cruzi infection that has a strong correlation to the radioimmunoprecipitation assay (RIPA) "gold standard" in the United States. Such a test could have utility in small blood banks for prescreening donors, as well as in cardiac transplantation evaluation. T. cruzi consensus and/or RIPA-positive sera from Central and South America were evaluated in enzyme immunoassays (EIAs). These included commercial panels from Boston Biomedica, Inc. (BBI) (n = 14), and HemaBio (n = 21). Other sources included RIPA-positive sera from the American Red Cross (ARC) (n = 42), as well as from Chile. Sera were tested with the multiepitope recombinant TcF. All but one of the BBI samples were positive and 7 of 21 HemaBio samples and 6 of 42 ARC samples were low positive or negative. This observation indicated the need for additional antigens. To complement TcF reactivity, we tested the sera with peptides 30, 36, SAPA, and 1.1, 1.2, and 1.3 His fragments of 85-kDa trans-sialidase. We identified a promising combination of the tested antigens and constructed a single recombinant protein, ITC6, that enhanced the relative sensitivity in U.S. blood donor sera compared to that of TcF. The data on its evaluation using RIPA-confirmed positive sera in EIA and lateral flow immunoassay studies are presented, along with an additional recombinant protein, ITC8.2, with two additional sequences for peptide 1 and Kmp-11. The latter, when evaluated in a dipstick assay with consensus positive sera, had a sensitivity of 99.2% and a specificity of 99.1%.