title: Production of refolded Toxoplasma gondii recombinant SAG1-related sequence 3 (SRS3) and its use for serodiagnosis of human toxoplasmosis.
abstract: SAG1-related sequence 3 (SRS3) is one of the major Toxoplasma gondii tachyzoite surface antigens and has been shown to be potentially useful for the detection of toxoplasmosis. This protein is highly conformational due to the presence of six disulfide bonds. To achieve solubility and antigenicity, SRS3 depends on proper disulfide bond formation. The aim of this study was to over-express the SRS3 protein with correct folding for use in serodiagnosis of the disease. To achieve this, a truncated SRS3 fusion protein (rtSRS3) was produced, containing six histidyl residues at both terminals and purified by immobilized metal affinity chromatography. The refolding process was performed through three methods, namely dialysis in the presence of chemical additives along with reduced/oxidized glutathione and drop-wise dilution methods with reduced/oxidized glutathione or reduced DTT/oxidized glutathione. Ellman's assay and ELISA showed that the protein folding obtained by the dialysis method was the most favorable, probably due to the correct folding. Subsequently, serum samples from individuals with chronic infection (n = 76), probable acute infection (n = 14), and healthy controls (n = 81) were used to determine the usefulness of the refolded rtSRS3 for Toxoplasma serodiagnosis. The results of the developed IgG-ELISA showed a diagnostic specificity of 91% and a sensitivity of 82.89% and 100% for chronic and acute serum samples, respectively. In conclusion, correctly folded rtSRS3 has the potential to be used as a soluble antigen for the detection of human toxoplasmosis.
authors.affiliation: Department of Biotechnology, Iranian Research Organization for Science and Technology (IROST), Tehran, Iran; Molecular Parasitology Laboratory, Department of Parasitology, Pasteur Institute of Iran, Tehran, Iran.
authors.forename: Abolfazl
authors.initials: A
authors.lastname: Mirzadeh
authors.affiliation: Department of Biotechnology, Iranian Research Organization for Science and Technology (IROST), Tehran, Iran. Electronic address: gitasaadat@gmail.com.
authors.forename: Geita
authors.initials: G
authors.lastname: Saadatnia
authors.affiliation: Molecular Parasitology Laboratory, Department of Parasitology, Pasteur Institute of Iran, Tehran, Iran.
authors.forename: Majid
authors.initials: M
authors.lastname: Golkar
authors.affiliation: Molecular Parasitology Laboratory, Department of Parasitology, Pasteur Institute of Iran, Tehran, Iran.
authors.forename: Jalal
authors.initials: J
authors.lastname: Babaie
authors.affiliation: Institute for Research in Molecular Medicine (INFORMM), Universiti Sains Malaysia, Penang, Malaysia.
authors.forename: Rahmah
authors.initials: R
authors.lastname: Noordin
mesh_terms: D000913:Antibodies, Protozoan / Q000097:blood / Q000276:immunology; D000953:Antigens, Protozoan / Q000096:biosynthesis / Q000737:chemistry / Q000235:genetics / Q000276:immunology; D004797:Enzyme-Linked Immunosorbent Assay / Q000379:methods; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism; D006801:Humans; D007074:Immunoglobulin G / Q000097:blood / Q000276:immunology; D058849:Protein Refolding; D011994:Recombinant Proteins / Q000096:biosynthesis / Q000737:chemistry / Q000235:genetics / Q000276:immunology; D014122:Toxoplasma / Q000737:chemistry / Q000235:genetics* / Q000276:immunology* / Q000378:metabolism; D014123:Toxoplasmosis / Q000097:blood / Q000175:diagnosis / Q000276:immunology
chemical_list: D000913:Antibodies, Protozoan; D000953:Antigens, Protozoan; D007074:Immunoglobulin G; D011994:Recombinant Proteins
keywords: In vitro refolding; Recombinant; SAG1-Related sequence 3(SRS3); Serodiagnosis; Toxoplasma gondii