Serodiagnostic assays for Taenia solium cysticercosis
Scheel, Christina Marie
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Programs to control transmission of Taenia solium cysticercosis will require a simple, yet efficacious serodiagnostic assay for large-scale surveillance of endemic populations to identify reservoirs of disease. To implement large-scale testing, two criteria must be met; the assay must be produced from an unlimited source of diagnostic material, and must have a rapid, low technology format. To meet these criteria, four synthetic T. solium antigens, TS14, TS18var1, TSRS1 and TSRS2var1, were applied to an enzyme-linked immunosorbent assay (ELISA) to determine their diagnostic potential. To compare the diagnostic efficacy of these antigens on a universal scale that was free of immunological bias, we constructed a standard reference curve using normal human immunoglobulin G (hIgG). The hIgG standard curve was utilized in each assay plate to control for interassay variations. Upon testing the synthetic antigens in ELISA against defined infection serum cohorts, we found that TS18var1 was the most sensitive for detecting cysticercal antibody, and TSRS1 the most specific, yet none of the antigens performed with high efficacy. Subsequently, each antigen was tested against the serum cohorts in the immunoblot format in which they were originally defined. Two of the antigen candidates, TSRS1 and TS18var1, proved to be of high sensitivity (96% and 98%, respectively) and high specificity (98% and 100%, respectively) when applied to this format. Although synthetic antigens provide an unlimited source of diagnostic material, the immunoblot is not a rapid, low-tech assay format. We partnered with a commercial diagnostic laboratory, Immunetics Inc., to apply synthetic TS18var1 and TSRS1, as well as a recombinant ™antigen, rGP50 to a patented assay format, the QuickELISA. All three antigens proved ™efficacious in this format. The quantitative aspect of the QuickELISA assays prompted us to explore the possibility of correlating immune response with disease status. We found that TS18var1 and rGP50 showed significant correlations (P = 0.01, P = 0.02, respectively) between improved disease and decreased seroreactivity in longitudinal serum samples of clinically ™defined neurocysticercosis patients. The cysticercosis QuickELISA assays are suitable for large-scale disease surveillance and may also provide clinicians with a practical tool for patient management.