Seroprevalence and associated risk factors of Toxoplasma gondii infection among pregnant mother in Makassar, Indonesia

Seroprevalence of anti-Toxoplasma gondii antibodies and associated risk factors in pregnant women in Somalia

Toxoplasma gondii infection is a worldwide protozoan parasitic disease caused by the parasite Toxoplasma gondii. T. gondii infection in gestation period can lead to fetal or neonatal death, and besides congenital defects. So far, there are no data available regarding T. gondii seropositivity and associated risk factors in pregnant women in Somalia. The investigations of these aspects were done in 403 pregnant women attending the antenatal care (ANC) at Benadir hospital, in Mogadishu city. Blood samples were collected and analyzed for anti-T. gondii antibodies by enzyme-linked immunosorbent assay (ELISA). IgG seropositivity to T. gondii was 45.2% (182/403). None of the women were positive for IgM antibodies. Considering the first, second, and third trimesters of pregnancy, women IgG seropositivity was 44.2%, 26.3%, and 67.7%, respectively (p < 0.05). There was no significant association between seropositivity and age, sociodemographic features, history of abortion, presence of cats in house, contact cats feces, contact with soil, consumption of raw vegetables/meats, blood transfusion, and drinking of unboiled milk (p>0.05). Routine serological screening for T. gondii should be integrated with other ANC services to identify potential infections with the parasite.

Development and evaluation of indirect enzyme-linked immunosorbent assay using recombinant dense granule antigen 7 protein for the detection of Toxoplasma gondii infection in cats in Thailand

Background and Aim:

Toxoplasma gondii is recognized as a zoonosis causing toxoplasmosis in animals globally. Cat is a definitive host of T. gondii and sheds oocyst through feces, which can infect human beings and animals through contaminated food ingestion. A precise diagnostic test is essential to prevent T. gondii infection in both humans and animals. This study aimed to develop and evaluate the pETite-dense granule antigen 7(GRA7)-based indirect enzyme-linked immunosorbent assay (ELISA) to detect T. gondii infection in cats.

Materials and Methods:

T. gondii-GRA7 was cloned and expressed in the Expresso^®small ubiquitin-related modifier (SUMO) T7 Cloning and Expression System. The recombinant pETite-GRA7 was purified using HisTrap affinity chromatography and confirmed using Western blot analysis. The recombinant protein was used to develop and evaluate the indirect ELISA for T. gondii infection detection. In total, 200 cat sera were tested using pETite-GRA7-based indirect ELISA and indirect fluorescent antibody test (IFAT). The statistical analysis based on Kappa value, sensitivity, specificity, positive predictive value, negative predictive value, χ² test, and receiver operating characteristic (ROC) curve was used to evaluate the performance of the test.

Results:

A 606 bp GRA7 polymerase chain reaction (PCR) product was obtained from T. gondii RH strain genomic DNA. The gene was cloned into the pETite™ vector and transformed to HI-Control Escherichia coli BL21 (DE3) for protein expression. Approximately 35 kDa of recombinant pETite-GRA7 was observed and Western blot analysis showed positive bands against anti-6-His antibody and positive-T. gondii cat serum. A sample of 0.5 μg/mL of pETite-GRA7 was subjected to indirect ELISA to detect T. gondii infection in the cat sera. The results showed sensitivity and specificity of pETite-GRA7-based indirect ELISA at 72% and 96%, respectively. An acceptable diagnostic performance was characterized by high concordant results (94%) and substantial agreement (Kappa value=0.65) with IFAT. The seroprevalence levels of ELISA and IFAT were 10% and 9%, respectively, and were not significantly (p>0.05) different. The expected performance of ELISA at different cutoff points using the ROC curve analysis revealed 89% sensitivity and 92% specificity at the cutoff value of 0.146, with a high overall assay accuracy (area under the curve=0.94).

Conclusion:

In this study, the pETite™ vector, N-terminal 6xHis SUMO fusion tag, was used to improve the solubility and expression level of GRA7. The recombinant pETite-GRA7 showed enhanced protein solubility and purification without special condition requirements. This pETite-GRA7-based indirect ELISA showed high concordant results and substantial agreement with IFAT. ELISA revealed an acceptable sensitivity and specificity. These initial data obtained from cats’ sera demonstrated that pETite-GRA7-based indirect ELISA could be a useful method for local serological diagnosis of T. gondii infection in cats in Thailand.