Evaluation of RE and B1 Genes as Targets for Detection of Toxoplasma gondii by Nested PCR in Blood Samples of Patients with Ocular Toxoplasmosis

Acta Parasitol. 2019 Jun;64(2):384-389. doi: 10.2478/s11686-019-00056-6.


Introduction: To evaluate B1 and RE genes as targets to detect Toxoplasma gondii, nested PCR is used in blood samples of patients with ocular toxoplasmosis.

Materials and methods: Following the measurement of IgG and IgM antibodies using indirect ELISA, IgG avidity and assessment of blood samples by nested PCR, the agreement between various test results was studied.

Results: From 117 patients, 77 (65.81%) were found to be positive for IgG anti-Toxoplasma antibody, 12 cases were positive for both IgG and IgM, and 1 patient was positive for IgM only. The detection limit for the RE-nested PCR assay was one T. gondii tachyzoite, whereas the limit for B1-nested PCR was five tachyzoites. Nested PCR results showed higher agreement with IgM test results than IgG test results.

Conclusion: The results of this study showed that nested PCR of peripheral blood is a useful and non-invasive method for detection of T. gondii in patients with OT, especially in case of recently acquired infections, and RE targeted assay is more sensitive than B1 targeted assay for this purpose.

Keywords: B1 gene; Nested PCR; Ocular toxoplasmosis; RE gene; Toxoplasma gondii.

Publication types

  • Evaluation Study

MeSH terms

  • Antibodies, Protozoan / blood
  • DNA, Protozoan / blood*
  • Humans
  • Immunoglobulin G / blood
  • Immunoglobulin M / blood
  • Polymerase Chain Reaction
  • Protozoan Proteins / blood*
  • Protozoan Proteins / genetics
  • Sensitivity and Specificity
  • Toxoplasma / genetics
  • Toxoplasma / isolation & purification*
  • Toxoplasmosis, Ocular / blood
  • Toxoplasmosis, Ocular / diagnosis*


  • Antibodies, Protozoan
  • DNA, Protozoan
  • Immunoglobulin G
  • Immunoglobulin M
  • Protozoan Proteins