Serological detection of T. gondii infection in humans using an immunochromatographic assay based on dense granule protein 7

Abstract Toxoplasma gondii causes toxoplasmosis, one of the world's most common parasitic diseases. It secretes large amounts of dense granule antigens (TgGRAs), which are crucial to the parasite's survivability. TgGRA7 is found abundantly on the surface of host cells, within the parasitophorous vacuole lumen and membrane, and the host cell cytosol. It stimulates a strong antibody response during acute and chronic infections. While it has been well utilized as an antigen for enzyme-linked immunosorbent assay (ELISA), only one report has documented its efficacy as an antigen for an immunochromatographic test (ICT) in pigs. To date, there is no study yet documenting its use for ICT in human toxoplasmosis. Here, we validated the efficacy of the TgGRA7-ICT we developed by testing 88 human sera. Results were compared with those obtained by ELISA based on TgGRA7, a commercial ELISA, and latex agglutination test (LAT). With high sensitivity, specificity, and kappa values, our TgGRA7-ICT results revealed very good agreement with standard test results. We also found a strong correlation between the relative ICT band intensity and absorbance values in the ELISA. Altogether, our data suggest that the current ICT with TgGRA7 is a reliable test for the diagnosis of human toxoplasmosis, which produced results similar to conventional serological methods. Thus, this can be used as a screening tool for routine testing of toxoplasmosis and a good option for point of care application. The present study also documents the first utilization of TgGRA7 as an antigen for ICT for the serodiagnosis of human toxoplasmosis.