Infection and Drug Resistance (Aug 2019)
Development, optimization, and validation of an in-house Dot-ELISA rapid test based on SAG1 and GRA7 proteins for serological detection of Toxoplasma gondii infections
Abstract
Aref Teimouri,1,2 Mohammad Hossein Modarressi,3 Saeedeh Shojaee,1 Mehdi Mohebali,1,4 Mostafa Rezaian,1 Hossein Keshavarz1,41Department of Medical Parasitology and Mycology, Tehran University of Medical Sciences, Tehran, Iran; 2Students Scientific Research Center, Tehran University of Medical Sciences, Tehran, Iran; 3Department of Medical Genetics, School of Medicine, Tehran University of Medical Sciences, Tehran, Iran; 4Center for Research of Endemic Parasites of Iran, Tehran University of Medical Sciences, Tehran, IranCorrespondence: Hossein KeshavarzDepartment of Medical Parasitology and Mycology, School of Public Health, Tehran University of Medical Sciences, PO Box 1417613191, Pour Sina Street, Ghods Avenue, Enghelab Avenue, Tehran, IranTel +98 218 895 1392Fax +98 218 895 1392Email [email protected]: The aim of the present study was to develop a simple, portable, and rapid assay for serodiagnosis of toxoplasmosis based on recombinant Toxoplasma gondii (T. gondii) SAG1 (rSAG1) and GRA7 (rGRA7) proteins.Methods: The rSAG1 and rGRA7 proteins were expressed in Escherichia coli (E. coli) and purified in a single step by immobilized metal ion affinity chromatography. The immunoreactivity of the recombinant antigens was tested in an in-house IgG and IgM Dot enzyme-linked immunosorbent assay (Dot-ELISA) for potential use in serodiagnosis of T. gondii infection.Results: Results from the comparison of in-house rSAG1-Dot-ELISA with ELISA for the detection of anti-Toxoplasma IgG and IgM include sensitivity of 83.7% and 81.2%, specificity of 90.2% and 89.3%, positive predictive values of 85.9% and 68.4%, and negative predictive values of 88.6% and 94.3%, respectively. Sensitivity of 66.2%, specificity of 81.2%, positive predictive values of 71.6%, and negative predictive values of 77.1% were concluded from in-house IgG rGRA7-Dot-ELISA. The sensitivity and specificity of IgM rGRA7-Dot-ELISA included 87.5% and 83.9%, respectively. Sensitivity and specificity of in-house Dot-ELISA for a combination of rSAG1 and rGRA7 included 87.5% and 91.1% for IgG and IgM, respectively. Sensitivity and specificity of a combination of rSAG1 and rGRA7 for the detection of IgM in suspected sera to acute toxoplasmosis were higher than those for the detection of IgG in sera with chronic infections (90.6% and 92% instead of 86.2% and 91.6%, respectively).Conclusion: The highlighted parameters of combined recombinant proteins were more significant than those of single recombinant proteins in in-house Dot-ELISA. These data suggest that the in-house Dot-ELISA based on rSAG1 and rGRA7 combination is a promising diagnostic tool with a similar sensitivity to the native antigens of T. gondii, which can be used for the serodiagnosis of toxoplasmosis in fields as well as less equipped laboratories.Keywords: Toxoplasma gondii RH strain, in-house Dot-ELISA, rSAG1, rGRA7, soluble tachyzoite antigen (STAg), recombinant proteins
