A combination of GRA3, GRA6 and GRA7 peptides offer a useful tool for serotyping type II and III Toxoplasma gondii infections in sheep and pigs

Front Cell Infect Microbiol. 2024 Apr 24:14:1384393. doi: 10.3389/fcimb.2024.1384393. eCollection 2024.

Abstract

The clinical consequences of toxoplasmosis are greatly dependent on the Toxoplasma gondii strain causing the infection. To better understand its epidemiology and design appropriate control strategies, it is important to determine the strain present in infected animals. Serotyping methods are based on the detection of antibodies that react against segments of antigenic proteins presenting strain-specific polymorphic variations, offering a cost-effective, sensitive, and non-invasive alternative to genotyping techniques. Herein, we evaluated the applicability of a panel of peptides previously characterized in mice and humans to serotype sheep and pigs. To this end, we used 51 serum samples from experimentally infected ewes (32 type II and 19 type III), 20 sheep samples from naturally infected sheep where the causative strain was genotyped (18 type II and 2 type III), and 40 serum samples from experimentally infected pigs (22 type II and 18 type III). Our ELISA test results showed that a combination of GRA peptide homologous pairs can discriminate infections caused by type II and III strains of T. gondii in sheep and pigs. Namely, the GRA3-I/III-43 vs. GRA3-II-43, GRA6-I/III-213 vs. GRA6-II-214 and GRA6-III-44 vs. GRA6-II-44 ratios showed a statistically significant predominance of the respective strain-type peptide in sheep, while in pigs, in addition to these three peptide pairs, GRA7-II-224 vs. GRA7-III-224 also showed promising results. Notably, the GRA6-44 pair, which was previously deemed inefficient in mice and humans, showed a high prediction capacity, especially in sheep. By contrast, GRA5-38 peptides failed to correctly predict the strain type in most sheep and pig samples, underpinning the notion that individual standardization is needed for each animal species. Finally, we recommend analyzing for each animal at least 2 samples taken at different time points to confirm the obtained results.

Keywords: GRA; Toxoplasma gondii; peptide; pig; serotyping; sheep.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Antibodies, Protozoan / blood
  • Antigens, Protozoan* / genetics
  • Antigens, Protozoan* / immunology
  • Enzyme-Linked Immunosorbent Assay* / methods
  • Genotype
  • Peptides / immunology
  • Protozoan Proteins* / genetics
  • Protozoan Proteins* / immunology
  • Serotyping* / methods
  • Sheep
  • Sheep Diseases* / diagnosis
  • Sheep Diseases* / parasitology
  • Swine
  • Swine Diseases / diagnosis
  • Swine Diseases / parasitology
  • Toxoplasma* / classification
  • Toxoplasma* / genetics
  • Toxoplasma* / immunology
  • Toxoplasmosis, Animal* / diagnosis
  • Toxoplasmosis, Animal* / parasitology

Substances

  • Protozoan Proteins
  • Antigens, Protozoan
  • GRA6 protein, Toxoplasma gondii
  • GRA7 protein, Toxoplasma gondii
  • Antibodies, Protozoan
  • Peptides

Grants and funding

The author(s) declare financial support was received for the research, authorship, and/or publication of this article. This work was funded by the TOXOSOURCES project, part of the European Union’s Horizon 2020 Research and Innovation Programme (773830) and the “Atracción de talento de la Comunidad de Madrid modalidad 2” grant from the Community of Madrid, Spain (2020-T2/BIO-19840). DA-S was partially supported by the postdoctoral research fellowships “Atracción de talento de la Comunidad de Madrid modalidad 2” (2020-T2/BIO-19840) and the European Union’s Horizon 2020 research and innovation programme UNA4CAREER under the Marie Skłodowska-Curie grant agreement No 847635. LT was supported by a mobility fellowship from the National Agency of Research and Innovation (ANII-Uruguay) and project FSSA_1_2019_1_159912 awarded to MF by ANII. NL-U was funded by the UCM-Santander/2018 predoctoral fellowship CT42/18-CT43/18.