Point-of-care diagnostic test for T. cruzi (Chagas) infection

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Project Summary Chagas disease, caused by infection with the parasite Trypanosoma cruzi, is the most prevalent parasitic disease in the western hemisphere, infecting 8-11 million individuals and with over 70 million at risk. The infection is transmitted by an insect vector, but can also be acquired through blood transfusion, organ transplant, or congenitally. Following a brief acute phase, the parasite persists for years in infected carriers, often asymptomatically, but can cause cardiomyopathy and other pathological conditions leading to severe morbidity and mortality. In the U.S., the prevalence of T. cruzi infection measured in immigrant populations has led to the implementation of blood screening assays to prevent transfusion transmission. The gradual encroachment of the insect vector into the southernmost regions of the U.S. has also raised the threat of autochthonous transmission. Chagas disease is challenging to diagnose due to the combination of genotypic and hence antigenic variation across its geographical range, complex immunological interactions with the human host, and cross-reactivities with other parasites. Serology has become the mainstay for diagnosis, especially for chronic infection, but the above challenges have hampered the accuracy of serologic tests such that multiple assays are commonly used in a triangulation algorithm to establish final results. The majority of those at risk for T. cruzi infection live in low-resource, underdeveloped areas where contact with the vector insects is hard to avoid, but medical care is relatively primitive and laboratory infrastructure is absent. For these reasons, rapid, point-of-care tests have become increasingly desirable as tools for diagnosis and epidemiological surveillance of Chagas disease. The current generation of Chagas rapid tests is limited by suboptimal performance, both with respect to sensitivity and specificity, however, largely due to the reliance on recombinant antigens which are specific to certain T. cruzi strains or lineages or stages of infection. To date, only one Chagas rapid test has been cleared by FDA. In this project, we propose to develop a rapid test for Chagas disease, based on a semi-purified native protein preparation from cultured T. cruzi termed TESA (Trypanosomal Excreted/Secreted Antigens). In preliminary studies by applicants and others, TESA immunoblots have shown clinical sensitivity and specificity approaching 100% across a range of genotypes and lineages. We have developed a purification procedure to enrich and concentrate the antigenic component of TESA, making it suitable for use in a lateral flow assay format. We have used this antigen in a prototype simplified lateral flow assay, which exhibited greater analytical sensitivity than the FDA-cleared rapid test and broad detection of T. cruzi infections across Latin America. In Phase I, we will develop a complete, TESA- based lateral flow rapid test suitable for point-of-care use in low-resource settings. TESA lateral flow test results will be read using a field-friendly, ultraportable, low-cost reader that will provide objective interpretation and enable wireless upload of data to local devices or remote servers. Phase II will support complete development to commercial stage, clinical evaluation and FDA submission of the TESA lateral flow test for in vitro diagnosis of Chagas disease.