Abstract
Toxoplasma gondii (T. gondii) is a ubiquitous protozoan parasite which causes a serious disease called toxoplasmosis. The high prevalence of T. gondii infection has attracted a great deal of interest in its diagnosis and treatment. The use of pure antigens shows high sensitivity and specificity, but challenges such as cross-reactivity remain diagnostic difficulties. The aim of this study was to use 3 surface antigens (SAGs) of T. gondii to design gene-encoding a multi-epitope and immunogenic protein as a serodiagnostic marker. The multi-epitope antigen was expressed using Escherichia coli BL21 (DE3) cells and purified using affinity chromatography. To evaluate acute toxoplasmosis, 95 human sera with anti-T. gondii IgG, 25 human sera without anti-T. gondii IgG and 6 serum samples with nosocomial infections were collected and submitted to an enzyme-linked immunosorbent assay (ELISA) analysis. The potential of purified protein as a diagnostic marker of T. gondii infection was also investigated using ELISA analysis. The western blot analysis for both protein expression and purification confirmed that the protein was expressed and purified successfully. The results of validation showed a sensitivity of 72.6% and a specificity of 90.3% for recombinant ELISA. Although this protein showed potential for detecting T. gondii, the sensitivity and specificity were lower than in tests that use the whole body of the parasite.
Highlights
Toxoplasma gondii, a ubiquitous protozoan parasite, is one of the most successful pathogens that can infect almost all warm-blooded animals, including humans
This protein showed potential for detecting T. gondii, the sensitivity and specificity were lower than in tests that use the whole body of the parasite
Nucleotide sequences for 3 surface antigens (SAG1, SAG2 and SAG3) of the extremely virulent RH strain of T. gondii were obtained from the National Center for Biotechnology Information (NCBI; Bethesda, USA) Nucleotide Database
Summary
Toxoplasma gondii, a ubiquitous protozoan parasite, is one of the most successful pathogens that can infect almost all warm-blooded animals, including humans. Toxoplasma gondii infection in humans occurs in 3 stages, including tachyzoite, bradyzoite and oocyst environmental stages. Tissue cysts containing bradyzoites appear in all warm-blooded animals, including humans. Resident surface proteins are among the virulence factors affecting the gliding, attachment and invasion of the parasite. Later investigations led to the detection of more surface antigens in T. gondii. These antigens have different roles in pathogenesis, including attachment and invasion of the parasite to the host cells and immune modulation. Surface antigens 2, 3, 4, 5, and SAG1related sequences (SRS) are other proteins on the surface of T. gondii tachyzoites and bradyzoites.[5]. The use of pure antigens shows high sensitivity and specificity, but challenges such as cross-reactivity remain diagnostic difficulties
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