Characterization and evaluation of a recombinant multiepitope peptide antigen MAG in the serological diagnosis of Toxoplasma gondii infection in pigs

• Published in: Parasites & vectors 2021-08, Vol.14 (1), p.408-408, Article 408
• Main Authors: Song, Yongle, Zhao, Yongjuan, Pan, Ke, Shen, Bang, Fang, Rui, Hu, Min, Zhao, Junlong, Zhou, Yanqin
• Format: Article
• Language: English
• Subjects: Agglutination tests; Animal diseases; Animal health; Animals; Antibodies; Antigens; Antigens, Protozoan - genetics; Antigens, Protozoan - immunology; blood serum; Complementary DNA; Cysts; Diagnosis; Diagnostic systems; Diseases; DNA; E coli; ELISA; Enzyme-linked immunosorbent assay; Epitopes; Epitopes - genetics; Epitopes - immunology; Escherichia coli; Farms; Hogs; Identification and classification; Immunoglobulin G; Immunoglobulin G - blood; Immunology; Indirect ELISA; Industry; Infections; Methods; Molecular diagnostic techniques; Molecular weight; Oocysts; Parasite antigens; Parasites; people; Peptides; Pig; Pork; Proteins; Protozoa; Recombinant proteins; Recombinant Proteins - genetics; Recombinant Proteins - immunology; Recombinants; Sensitivity analysis; Sensitivity and Specificity; Serodiagnosis; Serologic Tests - methods; Serologic Tests - standards; Serological detection; Serology; Serum; Specificity; Stability; Stability analysis; Swine; Swine Diseases - diagnosis; Swine Diseases - immunology; Swine Diseases - parasitology; Synthetic multiepitope antigen; Tachyzoites; Toxoplasma; Toxoplasma - genetics; Toxoplasma - immunology; Toxoplasma gondii; Toxoplasmosis; Toxoplasmosis, Animal - blood; Toxoplasmosis, Animal - diagnosis; Toxoplasmosis, Animal - immunology; Western blotting
• ISSN: 1756-3305; 1756-3305
• DOI: 10.1186/s13071-021-04917-w

Toxoplasmosis caused by Toxoplasma gondii is a serious disease threatening human and animal health. People can be infected with T. gondii by ingesting raw pork contaminated with cysts or oocysts. Serological test is a sensitive and specific method usually used for large-scale diagnosis of T. gondii infection in humans and animals (such as pigs). Commercial pig Toxoplasma antibody ELISA diagnostic kits are expensive, which limits their use; moreover, the wide antigen composition used in these diagnostic kits is still unclear and difficult to standardize. The multiepitope peptide antigen is a novel diagnostic marker, and it has potential to be developed into more accurate and inexpensive diagnostic kits. The synthetic multiepitope antigen (MAG) cDNA encoding a protein with epitopes from five T. gondii-dominant antigens (SAG1, GRA1, ROP2, GRA4, and MIC3) was designed, synthesized, and expressed in Escherichia coli BL21 (DE3) strain. The recombinant protein was detected through western blot with pig anti-T. gondii-positive and -negative serum, and then IgG enzyme-linked immunosorbent assay (ELISA) named MAG-ELISA was designed. The MAG-ELISA was evaluated in terms of specificity, sensitivity, and stability. The MAG-ELISA was also compared with a commercial PrioCHECK Toxoplasma Ab porcine ELISA (PrioCHECK ELISA). Finally, the trend of pig anti-T. gondii IgG levels after artificial infection with RH tachyzoites was evaluated using MAG-ELISA and two other ELISA methods (rMIC3-ELISA and PrioCHECK ELISA). MAG antigen could be specifically recognized by pig anti-T. gondii-positive but not -negative serum. MAG-ELISA showed high diagnostic performance in terms of specificity (88.6%) and sensitivity (79.1%). MAG-ELISA could be used for detecting anti-T. gondii IgG in the early stage of T. gondii infection in pigs (at least 7 days after artificial infection). Our results suggest that MAG antigen can be applied to specifically recognize anti-T. gondii IgG in pig, and MAG-ELISA has the potential for large-scale screening tests of T. gondii infection in pig farms and intensive industries.