Anti-Toxoplasma IgG assays: What performances for what purpose? A systematic review

Performances of ICT Toxoplasma IgG-IgM test in comparison with Vidas® toxo competition to determine the immune status against Toxoplasma gondii

Toxoplasmosis is a ubiquitous parasitic infection caused by Toxoplasma gondii (Tg). In immunocompetent people, the infection may be asymptomatic with the induction of an immune response that may prevent reinfection or transmission to the fetus in immune pregnant woman. In immunocompromised persons or seronegative pregnant woman with a primary infection during pregnancy, the infection may result in the loss of life, sight, cognition, and motor function in the immune-compromised person or immunologically immature fetus. The objective of this study was to evaluate a new immunochromatographic test Toxoplasma ICT IgG-IgM (ICT) that allows detection of specific anti-Tg immunoglobulins G (Ig G) and M (Ig M). We included 1145 prospectively obtained sera and 376 samples selected for specificity or sensitivity studies. The performance of ICT was compared using Vidas® Toxo Competition (TXC) and Toxoscreen®. In case of discrepancy, Vidas® Toxo Ig G or Ig M and LDBIO Toxo II IgG western blot were used to establish definitive results by additional methods. Sensitivity and specificity of ICT were respectively 99.3% and 100%. In comparison, Toxoscreen®'s sensitivity was 100% and the specificity was 99.8%. TXC had a sensitivity of 98.7% with a specificity of 99.1%. ICT has excellent performance even for low Ig G titers, especially in immunocompromised patients, and confirms the specificity of isolated Ig M. This ICT provides reliable results easily and quickly. This screening technique is not designed to differentiate the Ig M from Ig G. When positive, additional tests may be necessary.

Past and present seroprevalence and disease burden estimates of Toxoplasma gondii infections in Germany: An appreciation of the role of serodiagnostics

Toxoplasmosis is one of the major foodborne parasitic diseases in Germany, with 49% of its population chronically infected with its causative agent, Toxoplasma gondii. Although the acute disease is usually benign in immunocompetent individuals, it is a threat for immunocompromised patients as well as for fetuses of seronegative mothers. As a result of infection, congenital and ocular toxoplasmosis can have serious lifelong consequences. Here I will highlight the epidemiologic situation, from its past in the two separate parts of Germany, to its unification 30 years ago and up to the present day. The main identified risk factor for infection in Germany is thought to be the consumption of undercooked or raw meat or sausages. However, the relative impact of this risky eating habit as well as that of other risk factors are changing and are discussed and compared to the situation in the Netherlands. Finally, the importance of robust and efficient high-throughput serological assays for obtaining reliable epidemiological data, on which public health decisions can be made, is highlighted. The potential of bead-based multiplex assays, which allow the incorporation of multiple antigens with different analytical properties and thus yield additional information, are described in this context. It illustrates the interdependence of new analytic assay developments and sound epidemiology, a foundation that decades-old data from Germany did not have.

Synchronous Left Ventricular and Endocranial Mass

Myocardial cysts represent a miscellaneous and infrequent spectrum of conditions, with each of them coming from a different etiological background. Congenital myocardial cysts, neoplasia, cysts of infectious origin (bacterial, viral, or parasitic), and cardiac pathologies that may fake cystic content are all encompassed in this group. Although most patients are asymptomatic, some may occasionally present with obstruction, valvular dysfunction, or heart failure. Even more uncommon is the coexistence of a myocardial cyst with other extracardiac locations causing extracardiac symptoms. In this direction, the coexistence of a myocardial and endocranial cyst is extremely rare and can cause symptomatology from the affected organs (e.g., seizures). Cardiac investigation in this context is mainly dependent on non-invasive diagnostic modalities, and laboratory procedures. In this case report, we present a 26-year-old Congolese male admitted with dyspnea and epileptic seizures. Echocardiography revealed left ventricular and both mitral and tricuspid valve dysfunction and the presence of two myocardial cysts, while brain computed tomography showed an additional frontal cystic lesion. A precise diagnostic workup with a combination of non-invasive imaging, laboratory results, and epidemiology data assisted the diagnosis and guided the most suitable therapeutic choice.

Toxoplasmosis Screening during Pregnancy in a Romanian Infectious Diseases Tertiary Center: Results of a 15 Years Follow-Up Program

Maternal infection with Toxoplasma gondii during pregnancy may have serious consequences for the fetus. In Romania, screening for toxoplasmosis is included in the first antenatal visit. A retrospective study was performed on all toxoplasmosis antenatal screening patients between May 2008 and February 2023. Twenty-seven thousand one hundred sixty-nine (27,169) pregnant women presented for prenatal screening once (22,858) or several times: during the same pregnancy (209) or during multiple pregnancies (4102). Thirty-one thousand six hundred fifty-eight (31,658) tests for IgM and IgG antibodies were performed. Nine thousand eighty-three (9083) tests (28.69%), corresponding to 7911 women (29.12%), were positive for IgG antibodies. The seroprevalence increased with patients' age, decreased in time intervals, and was more frequently associated with rural residence. At risk for acquiring the infection during the pregnancy were women with negative anti-Toxoplasma IgG antibodies (70.88%), but only 0.9% of them presented for rescreening during the same pregnancy. Acute Toxoplasma infection (ATI) was suspected in 44 patients (0.16%) due to IgG seroconversion and/or low or borderline IgG avidity. A questionnaire follow-up interview was performed, and no congenital toxoplasmosis was identified in children born from mothers with probable ATI. Our study demonstrates poor compliance with the screening program in the Romanian population.

Serological diagnosis of toxoplasmosis in pregnancy: comparison between a manual commercial ELISA assay and the automated VIDAS® kit

Knowledge of the toxoplasmosis serological status in pregnant women is important to allow adequate management for the prevention of congenital toxoplasmosis of those who are not immunized. Serological screening is generally carried out using commercial kits to determine the presence or absence of immunoglobulins M or G in the maternal blood. Robust results are therefore needed. We evaluated the performances of a commercial ELISA assay composed of several recombinant parasite antigens and of a commercial assay using parasite lysate to determine the serological status against Toxoplasma gondii of African pregnant women. A recruitment of 106 pregnant women during their third trimester of pregnancy was carried out in Benin. Serologies were performed with recomWell Toxoplasma IgM and IgG kits. Subsequently, the serological assays were carried out by an automaton method with the VIDAS^® TOXO IgM and IgG II kits. Here we compared recomWell Toxoplasma to VIDAS^® TOXO results. Reproducibility tests of the recomWell kits were assessed following the discrepancies observed in the results. Of 106 plasmas tested, 47 showed anti-T. gondii IgG (44.3%), including 5 with IgM and high IgG avidity (4.7%). Of the two techniques, VIDAS^® TOXO was more robust and specific for IgG while the recomWell Toxoplasma gave more false positive results. The combination of several techniques for the determination of serological toxoplasmosis status remains relevant. Methods using native proteins are closer to the reality of the environment. Therefore, kits using recombinant proteins should be tested on highly geographically diverse populations to refine their composition.

Screening for the Detection of Toxoplasma gondii IgG, IgM and IgA in Females of Reproductive Age from Western Romania

Toxoplasma gondii, a zoonotic protozoan parasite, has the capacity to infect the fetus if the pregnant woman primarily acquires the infection during pregnancy. We evaluated the prevalence of T. gondii IgG, IgM and IgA antibodies in women of reproductive age residing in Western Romania. We also assessed the value of adding a T. gondii IgA test to the serologic panel for the diagnosis of toxoplasmosis, including the detection of a recently acquired infection. Serologic testing to demonstrate the presence of T. gondii IgG antibodies was conducted in 1317 females aged 15−45 years. T. gondii IgM and IgA antibody tests were performed in those with detectable IgG antibodies and IgG avidity test was performed if IgM and/or IgA screening test results were positive. T. gondii IgG were detected in 607 (46.09%; 95%CI: 43.41−48.79) of 1317 study participants and IgG seroprevalence tended to increase with age from 35.44% (95%CI: 29.89−41.30) in age group 15−24 years to 62.85% (95%CI: 56.57−68.82) in age group 35−45 years, showing a significant age-associated increase (p < 0.001). Of the 607 persons with detectable T. gondii IgG antibodies, T. gondii IgM antibodies were demonstrated in 8.90% (95%CI: 6.88−11.43), T. gondii IgA in 1.65% (95%CI: 0.90−3.01) and both T. gondii IgM and IgA in 0.99% (95%CI: 0.45−2.14). The prevalence of IgA antibodies tended to decrease with increasing avidity, from 75% (95%CI: 19.41−99.37) in samples with low avidity to 11.76% (95%CI: 4.44−23.87) in those with high avidity (p = 0.01). Of the study participants who were positive for both T. gondii IgM and IgA antibodies, 66.67% had low or equivocal IgG avidity test results compared to 6.25% who tested positive for IgM, were negative for IgA and in whom low or equivocal IgG avidity test results were noted (p = 0.001). This study indicates that in Western Romania, T. gondii IgG seroprevalence is high in females of reproductive age and T. gondii IgA antibodies may be rarely detected during a serologic screening. However, in individuals with demonstrable T. gondii IgG and IgM antibodies, testing for T. gondii IgA may improve the rate for the detection of a recently acquired toxoplasmosis.

Toxoplasma gondii Infection Among Institutionalized Children with Down syndrome in Sana'a city, Yemen: Implications of Low IgG Seroprevalence

Purpose

To assess the IgG seroprevalence of Toxoplasma gondii as an indicator of past exposure and immunity against infection among children with Down syndrome (DS) in Sana’a city, Yemen. This preliminary study is justified by the primary immunodeficiency of children with DS and the opportunistic nature of the parasite, considering the vague situation of anti-Toxoplasma IgG seroprevalence among children with DS because of neglecting its study on local and global scales.

Methods

This descriptive, facility-based, cross-sectional study was conducted among 107 children with DS hosted in six randomly selected rehabilitation centers for children with special needs in Sana’a city. Demographics of children and their mothers’ knowledge of toxoplasmosis were collected using a pre-designed, structured questionnaire. Anti-Toxoplasma IgG antibodies were measured in the sera of children using electrochemiluminescence assay.

Results

Of 107 children with DS, 3 (2.8%) were seropositive for anti-Toxoplasma IgG. Approximately two-thirds (71/106) of the mothers of children with DS were aware of toxoplasmosis. Of whom, 83.1% (59/71) were aware of its congenital complications.

Conclusion

The majority of children with DS in Sana’a city are seronegative for anti-Toxoplasma IgG, where the seropositivity rate is lower than 3.0%. Therefore, children with DS are non-immune and susceptible to the acquisition of primary infections during their life. Further analytical studies are recommended to determine whether the defective immune response of children with DS is associated with false seronegativity, to assess the role of their mothers’ knowledge in reducing their exposure to infection if they were confirmed truly seronegative and to identify the predictors of infection among them.

Serological diagnosis of toxoplasmosis: evaluation of the commercial test recomLine Toxoplasma IgG immunoblot (Mikrogen) based on recombinant antigens

Background: IgG detection to determine immune status to Toxoplasma gondii infection and seroconversion mainly relies on ELISA techniques and, if necessary, on a confirmatory test, Western blot. This study evaluated the performance of the recomLine Toxoplasma IgG immunoblot (IB-recomLine) (Mikrogen) as a confirmatory test on a large number of sera. A total of 171 sera were selected (113 patients) and had previously been analyzed by two ELISA tests, ARCHITECT (Abbott) and VIDAS (bioMérieux) ± LDBIO-Toxo II IgG Western blot (WB-LDBIO) (LDBio). The sera were classified into three groups: group 1 included 50 sera without difficulty in interpreting the IgG results (patients with documented past infection or uninfected); group 2 included 47 sera with difficulty in interpreting the ELISA results; and group 3 included 74 sequential sera from 25 pregnant women with seroconversion. Results: In group 1, overall IgG agreements were 94% and 90% with ARCHITECT and VIDAS, respectively. In group 2, low agreement was observed between IB-recomLine and WB-LDBIO, with eight false-positive and 13 false-negative results. In group 3, 4/13 seroconversions were detected earlier with IB-recomLine compared to other tests. Conclusions: IB-recomLine allowed for earlier diagnosis of toxoplasmic seroconversion compared to both ELISA tests and WB-LDBIO but led to insufficient performance to confirm the immune status when ELISA results were discordant or equivocal.