Development of specific immunoglobulins G, M, and A following primary Toxoplasma gondii infection in pregnant women

Comparison of a Commercial Enzyme-Linked Immunosorbent Assay (ELISA) with the Modified Agglutination Test (MAT) for the Detection of Antibodies against Toxoplasma gondii in a Cohort of Hunting Dogs

Toxoplasmosis is a zoonotic disease, caused by the protozoan Toxoplasma gondii, affecting most warm-blooded animals. Assessing the seroprevalence of T. gondii in different animal species gives a good estimate of the global circulation of the parasite and the risk for human infections. However, the seroprevalence of T. gondii in dogs is not studied as much as other species, despite their close contact with wildlife and humans in rural or urban environments and evidence that dogs can also be a potential source for human contaminations. A commercial enzyme-inked immunosorbent assay (ELISA) kit to detect anti-T. gondii antibodies in sera of hunting dogs potentially naturally infected, was compared to the modified agglutination test (MAT), used as the reference method. The ELISA presented a sensitivity of 76.5% (CI 95%: 60.0–87.6) and a specificity of 87.7% (CI 95%: 76.7–93.9) and a substantial agreement with the MAT for the detection of canine anti-T. gondii antibodies. Both tests can therefore be used widely for epidemiology studies on T. gondii infections in dogs. With a mean seroprevalence of T. gondii infection in hunting dogs from northern Algeria of 36.8% (CI 95%: 34.9–38.7), this study also highlights the importance of T. gondii seroprevalence studies in companion animals to assess infectious risk for human populations.

Anti-Toxoplasma gondii IgM Long Persistence: What Are the Underlying Mechanisms?

Diagnosis of Toxoplasma gondii acute infection was first attempted by detection of specific IgM antibodies, as for other infectious diseases. However, it was noted that this immunoglobulin declines slowly and may last for months or even years. Apart from the diagnostic problem imposed on clinical management, this phenomenon called our attention due to the underlying phenomena that may be causing it. We performed a systematic comparison of reports studying IgM antibody kinetics, and the data from the papers were used to construct comparative plots and other graph types. It became clear that this phenomenon is quite generalized, and it may also occur in animals. Moreover, this is not a technical issue, although some tests make more evident the prolonged IgM decay than others. We further investigated biological reasons for its occurrence, i.e., infection dynamics (micro-reactivation–encystment, reinfection and reactivation), parasite strain relevance, as well as host innate, natural B cell responses and Ig class-switch problems inflicted by the parasite. The outcomes of these inquiries are presented and discussed herein.

Comparison of a commercial ELISA and indirect hemagglutination assay with the modified agglutination test for detection of Toxoplasma gondii antibodies in giant panda (Ailuropoda melanoleuca)

Toxoplasma gondii is a worldwide-distributed zoonotic protozoan parasite which causes toxoplasmosis and has a significant effect on public health. In the giant panda (Ailuropoda melanoleuca), toxoplasmosis can cause asymptomatic infections, reproductive disorder and even death, which poses a serious threat to the conservation of this rare protected species. Therefore, serological investigation of T. gondii is essential to understanding its risk to giant pandas, however, there are no specific testing kits for giant pandas. Previous research has used MAT as the reference method for screening T. gondii, to investigate this further, this study focused on the agreement comparing of MAT with ELISA and IHA tests for detecting T. gondii antibodies in 100 blood samples from 55 captive giant pandas in Chengdu, China. The results showed 87.0%, 87.0%, 84.0%, samples were sero-positive for T. gondii using ELISA (kits a, b, c), respectively, while MAT and IHA tests were 84.0% and 9.0% sero-positive, respectively. There was no significant difference between MAT and the three ELISA kits and these two methods had substantial agreement (0.61 < қ ≤ 0.80). Meanwhile, there was a significant difference (P < 0.001) between MAT and IHA, and these two methods had only a slight agreement (қ ≤ 0.20). The relative sensitivity of the ELISA (kits a, b, c) were 89.0%, 91.5% and 95.1%, and the specificity were 86.7%, 80.0% and 80.0%, respectively, which showed these three ELISA kits all had great accuracy. It is suggested that MAT is the recommended test method for primary screening T. gondii in giant pandas and then verified by ELISA.

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It's the first report to compare the agreement of the three test kits for detecting T. gondii antibodies in giant panda.

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No significant difference and substantial agreement between MAT and ELISA, slight agreement, meanwhile, the contrary result between MAT and IHA.

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The relative sensitivity of ELISA kits was 89%, 91.5% and 95.1%, and the specificity was 86.7%, 80% and 80%, respectively.

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The two commonly used commercial MAT and ELISA kits tested were valuable tools for T. gondii diagnosis for giant panda.

Comparisons of Toxoplasma gondii Prevalence in Rural and Urban Areas of Al-Najaf Province of Iraq Using Serological Methods

Toxoplasma gondii (T. gondii) is an intracellular protozoan parasite that multiplies within the host cell and causes the disease toxoplasmosis. T. gondii is distributed worldwide and is capable of infecting almost all warm-blooded animals. The current study was conducted in several urban and rural regions in AL-Najaf province of Iraq from September 2020 to April 2021. In total, 190 blood samples were collected and screened for T. gondii IgG and IgM antibodies using Rapid Diagnostic immunochromatographic test and the enzyme-linked immunosorbent assay (ELISA). These two tests were performed on 5 ml of blood samples. The results of the ICT test showed that 80 (42.1%) samples were positive for IgG; however, no IgM positive sample was recorded. The results of ELISA revealed that 27 (33.7%) and 4 (5%) samples were positive for T. gondii IgG and IgM antibodies, respectively. The estimated incidence of toxoplasmosis increased significantly in the 21-30 years age group and females (P<0.05), compared to other groups. The wide prevalence of toxoplasmosis was observed in Iraq, especially in Najaf province, which was reflected in the results of the study after taking random samples from different places with no symptoms of the disease. Therefore, all members of the community should undergo periodic examinations to diagnose possible infection through the most accurate tests.

Tubulointerstitial nephritis and uveitis syndrome following meningitis and systemic lymphadenopathy with persistent Toxoplasma immunoglobulin M: a case report

Background

Tubulointerstitial nephritis and uveitis syndrome is a rare lymphocyte-related oculorenal inflammatory disease presumed to be associated with drug use and infectious agents. Toxoplasma gondii is one of such pathogens that could exhibit encephalitis, meningitis, and uveitis in immunocompromised or in some immunocompetent individuals. If the immunoglobulin M of Toxoplasma is positive on screening, the interpretation of the result is not simple, especially when immunoglobulin M stays positive persistently.

Case presentation

A 34-year-old Asian male developed fever, headache, and lymphadenopathy with tenderness, which was initially diagnosed as meningitis. Antibiotics were started, and diclofenac sodium was used for the fever. Although his symptoms were alleviated in a week by the treatment, gradual decline in renal function was noted, prompting a renal biopsy that indicated acute granulomatous interstitial nephritis. A week later, tenderness in both eyes with blurred vision appeared and revealed iritis and keratic precipitations in both eyes; hence, the diagnosis of acute tubulointerstitial nephritis and bilateral uveitis syndrome was made. Toxoplasma gondii-specific immunoglobulin G and immunoglobulin M titers were both positive. Although we could not rule out recent infection of Toxoplasma gondii, which may cause uveitis initially, Toxoplasma immunoglobulin G avidity test indicated a distant infection, which allowed us to rule out meningitis and uveitis as responsible for the complication of recent Toxoplasma gondii infection. Drug-induced lymphocyte stimulation test, or lymphocyte transformation test of diclofenac sodium, was solely positive among the tested drugs. Uveitis was alleviated only with ophthalmic steroid, and renal function returned to normal without administration of systemic steroid.

Conclusions

We experienced a case of diclofenac-induced tubulointerstitial nephritis and uveitis syndrome. In ruling out infections, Toxoplasma immunoglobulin M was persistently positive, and Toxoplasma immunoglobulin G avidity test indicated a “distant” infection. From these two results, we ruled out recent infection. However, it should be noted that “distant” infection indicated by commercial immunoglobulin G avidity is still a multiplex profile consisting of reinfection, reactivation, and latent infection. Narrowing down the infection profile of Toxoplasma is challenging in some cases. Therefore, careful diagnosis and extended follow-up of such patients are needed.

Evaluation of CpG-ODN-Adjuvanted Toxoplasma Gondii Virus-Like Particle Vaccine upon One, Two, and Three Immunizations

Successful vaccines against specific pathogens often require multiple immunizations and adjuvant usage. Yet, assessing the protective efficacy of different immunization regimens with adjuvanted Toxoplasma gondii vaccines remains elusive. In this study, we investigated the vaccine efficacy induced by CpG-ODN-adjuvanted T. gondii virus-like particles (VLPs) after challenge infection with T. gondii (ME49) in mice (BALB/c) upon one, two, and three immunizations. Immunization with adjuvanted T. gondii VLPs induced higher levels of T. gondii-specific IgG and/or IgA antibody responses, germinal center (GC) B cells, total B cells, and CD4⁺ and CD8⁺ T cells compared with unadjuvanted VLPs. Increasing the number of immunizations was strongly correlated with enhanced protective immunity against T. gondii in mice, with the highest protection being demonstrated in mice thrice-immunized with either adjuvanted T. gondii VLPs or VLPs alone. Notably, lesser bodyweight reductions and cerebral cyst counts were observed in mice receiving multiple immunizations with the adjuvanted VLPs, thereby confirming the effectiveness of adjuvanted boost immunizations. These results demonstrated that multiple immunizations with T. gondii VLPs is an effective approach, and the CpG-ODN can be developed as an effective adjuvant for T. gondii VLP vaccines.

Role of Toxoplasma IgA as Part of a Reference Panel for the Diagnosis of Acute Toxoplasmosis during Pregnancy

This study evaluated the usefulness of adding the Toxoplasma gondii IgA antibody enzyme-linked immunosorbent assay (ELISA) to the serologic panel of tests done for the diagnosis of acute toxoplasmosis in pregnant women in a reference laboratory in the United States. We conducted a retrospective study of 690 consecutive pregnant women with positive T. gondii IgG antibody test results who also had T. gondii IgA and IgM antibody tests performed.

This study evaluated the usefulness of adding the Toxoplasma gondii IgA antibody enzyme-linked immunosorbent assay (ELISA) to the serologic panel of tests done for the diagnosis of acute toxoplasmosis in pregnant women in a reference laboratory in the United States. We conducted a retrospective study of 690 consecutive pregnant women with positive T. gondii IgG antibody test results who also had T. gondii IgA and IgM antibody tests performed. Patients were defined as acutely or chronically infected with T. gondii based on a panel of serologic tests performed at the Palo Alto Medical Foundation Toxoplasma Serology Laboratory (PAMF-TSL). Among the 81 women who were positive by T. gondii IgA antibody ELISA testing, 61 (75.3%) were acutely infected with T. gondii, while of the 547 who were negative by IgA testing, only 24 (4.4%) were acutely infected (P < 0.001). Among the 71 women who were positive by both IgA and IgM antibody tests, 61 (85.9%) were acutely infected, whereas 24 (19.2%) of the 125 women who were positive by only the IgM ELISA were acutely infected (P < 0.001). These results demonstrate that pregnant women with T. gondii IgA antibodies are more likely than pregnant women without T. gondii IgA antibodies to have had a recent infection with T. gondii. Toxoplasma IgA antibody testing can therefore improve the accuracy of a serologic panel for the diagnosis of acute toxoplasmosis during pregnancy. Physicians who ordered testing only for T. gondii IgG and IgM should also request additional testing for IgA and IgG avidity, if both IgG and IgM are positive. This further testing should, ideally, be performed in a reference laboratory.

Seromolecular assess of Toxoplasma gondii infection in pregnant women and neonatal umbilical cord blood

Toxoplasmosis is considered as one of the most prevalent human parasitic infections that can be transmitted from mother to the fetus. The onset of toxoplasmosis during pregnancy has clinical complications including spontaneous abortion, preterm labor, stillbirth and fetal abnormalities. The aim of this study was to investigate the prevalence of Toxoplasmosis infection in pregnant women and their infants in Lorestan province, Western Iran. Blood and sera samples were collected from 98 pregnant women and their infants. All collected samples were examined for Toxoplasma gondii infection by serological tests (ELISA IgM & IgG) and PCR assay. Among the 98 samples of mother and umbilical cord prevalence of anti-Toxoplasma IgG, was 34/98 (34.69 %) and 33/98 (33.67 %), respectively. All pregnant women were negative for, anti-Toxoplasma IgM while it was found in 5/98 (5.1 %) of umbilical cords. Based on PCR analysis, Toxoplasma infection was detected in 5 (5.1 %) and 7 (7.14 %) of mother and umbilical cords, respectively. Molecular test along with evaluation of IgM (P <0.001) and IgG (P = 0.001) were significantly correlated.

Isothermal PCR for Feasible Molecular Diagnosis of Primary Toxoplasmosis in Women Recently Experienced Spontaneous Abortion

AIM:

The current study aimed to assess the practicability of a simple loop-mediated isothermal amplification (LAMP) about real-time quantitative PCR to diagnose primary toxoplasmosis among high-risk pregnant women.

METHODS:

Cloned Toxoplasma samples were used to calculate the analytical sensitivity while specificity was assessed using pooled DNA samples extracted from other parasitic stages.

RESULTS:

Both techniques showed 100% sensitivity and specificity and then applied to detect recent Toxoplasma infection in peripheral blood of 77 IgG negative women out of a total 139 women lately experienced spontaneous abortion. The 2 techniques obtained positive results in 8 samples confirming primary toxoplasmosis.

CONCLUSION:

Generally, LAMP assay is a simple, cost-effective molecular technique can be completed in less than half an hour to diagnose primary Toxoplasma infection. The technique can be applied in a minimally equipped laboratory by ordinary workers to screen the vulnerable groups. Further analysis using larger samples with the quantitative approach is recommended to confirm the sensitivity of this emergent molecular technique.

Association between Toxoplasma gondii infection and history of blood transfusion: a case-control seroprevalence study

Objectives

This study was performed to determine the association between seropositivity to Toxoplasma gondii and a history of blood transfusion.

Methods

Patients who had undergone blood transfusion (n = 410) and age- and sex-matched controls who had not undergone blood transfusion (n = 1230) were examined for anti-T. gondii IgG and IgM antibodies using enzyme-linked immunoassays.

Results

Anti-T. gondii IgG antibodies were detected in 57 (13.9%) patients and in 129 (10.5%) controls with a borderline difference [odds ratio (OR) = 1.37, 95% confidence interval (CI) = 0.98–1.92]. High anti-T. gondii IgG antibody levels (>150 IU/mL) were found in 27 (47.4%) of the 57 anti-T. gondii IgG-positive patients and in 37 (28.7%) of the 129 anti-T. gondii IgG positive controls with a significant difference (OR = 2.23, 95% CI = 1.17–4.26). Anti-T. gondii IgM antibodies were found in 13 (22.8%) of the 57 seropositive patients and in 37 (28.7%) of the 129 seropositive controls, but the difference was not significant (OR = 0.73, 95% CI = 0.35–1.52). Seroprevalence was significantly higher in patients aged >50 years than in controls of the same age and in female patients than in female controls.

Conclusions

These findings indicate that a history of blood transfusion is a risk factor for T. gondii infection.

Evaluation of serological and molecular tests used to identify Toxoplasma gondii infection in pregnant women attended in a public health service in São Paulo state, Brazil

Toxoplasmosis during pregnancy can have severe consequences. The use of sensitive and specific serological and molecular methods is extremely important for the correct diagnosis of the disease. We compared the ELISA and ELFA serological methods, conventional PCR (cPCR), Nested PCR and quantitative PCR (qPCR) in the diagnosis of Toxoplasma gondii infection in pregnant women without clinical suspicion of toxoplasmosis (G1=94) and with clinical suspicion of toxoplasmosis (G2=53). The results were compared using the Kappa index, and the sensitivity, specificity, positive predictive value and negative predictive value were calculated. The results of the serological methods showed concordance between the ELISA and ELFA methods even though ELFA identified more positive cases than ELISA. Molecular methods were discrepant with cPCR using B22/23 primers having greater sensitivity and lower specificity compared to the other molecular methods.

Results of the National External Quality Assessment for Toxoplasmosis Serological Testing in China

Background

Toxoplasmosis is typically diagnosed by serologic testing. External quality assessment (EQA) of clinical laboratories could ensure the accuracy and reliability of serological tests. We assessed the quality of toxoplasma serological assays in Chinese clinical laboratories by an EQA performed between 2004 and 2013 by the National Center for Clinical Laboratories.

Methodology and Findings

EQA panels were prepared and shipped at room temperature to participating laboratories that employed toxoplasma IgG and IgM serological detection. By 2013, 5,384 EQA test reports for toxoplasma-specific IgM and 2,666 reports for toxoplasma-specific IgG were collected. Enzyme-linked immunosorbent (ELISA) and chemical immunofluorescent assays were the most commonly used detection methods. The overall coincidence rates of negative samples were better than those of positive samples. The overall EQA score for toxoplasma-specific IgM detection ranged between 84.3% and 99.6%. The ratio of laboratories that achieved correct IgG detection ranged from 61.1% to 99.3%. However, the inter- and intra-assay variabilities were found to be considerable. The most common problem was failure to detect low titers of antibody.

Conclusion

The EQA scheme showed an improvement in toxoplasma serological testing in China. However, further optimization of assay sensitivity to detect challenging samples remains a future challenge.

A review on human toxoplasmosis

Toxoplasmosis is a worldwide infection caused by the intracellular parasite Toxoplasma gondii. At least a third of the world human population are infected with the parasite, making it one of the most successful parasitic infections. Primary maternal infection may cause health-threatening sequelae for the foetus, or even cause death in uterus. Reactivation of a latent infection in immune deficiency conditions such as AIDS and organ transplantation can cause fatal toxoplasmic encephalitis. Toxoplasmosis is a major cause of retinochoroiditis, especially in individuals with an impaired immune system. Despite the usually 'asymptomatic' nature of the infection, a significant burden imposed by the parasite necessitates the implementation of effective means for the prevention, diagnosis, and management of this disease. Laboratory diagnosis, i.e. PCR and serologic assays, plays the main role in the diagnosis of congenital infection and assists in the confirmatory diagnosis of toxoplasmic encephalitis and ocular toxoplasmosis. Here, we briefly review general aspects of Toxoplasma infection and focus on the diagnostic methods currently used in medical laboratories for the diagnosis of Toxoplasma infection.

Toxoplasma gondii infection in pregnant women in China

Toxoplasmosis, caused by the protozoan parasite Toxoplasma gondii, is one of the most common parasitic infections in humans. Primary infection in pregnant women can be transmitted to the fetus leading to miscarriage or congenital toxoplasmosis. Carefully designed nationwide seroprevalence surveys and case-control studies of risk factors conducted primarily in Europe and America, have shaped our view of the global status of maternal and congenital infection, directing approaches to disease prevention. However, despite encompassing 1 in 5 of the world's population, information is limited on the status of toxoplasmosis in China, partly due to the linguistic inaccessibility of the Chinese literature to the global scientific community. By selection and analysis of studies and data, reported within the last 2 decades in China, this review summarizes and renders accessible a large body of Chinese and other literature and aims to estimate the seroprevalence in Chinese pregnant women. It also reviews the prevalence trends, risk factors, and clinical manifestations. The key findings are (1) the majority of studies show that the overall seroprevalence in Chinese pregnant women is less than 10%, considerably lower than a recently published global analysis; and (2) the few available appropriate studies on maternal acute infection suggested an incidence of 0·3% which is broadly comparable to studies from other countries.

Development and clinical evaluation of a rapid serodiagnostic test for toxoplasmosis of cats using recombinant SAG1 antigen

Rapid serodiagnostic methods for Toxoplasma gondii infection in cats are urgently needed for effective control of transmission routes toward human infections. In this work, 4 recombinant T. gondii antigens (SAG1, SAG2, GRA3, and GRA6) were produced and tested for the development of rapid diagnostic test (RDT). The proteins were expressed in Escherichia coli, affinity-purified, and applied onto the nitrocellulose membrane of the test strip. The recombinant SAG1 (rSAG1) showed the strongest antigenic activity and highest specificity among them. We also performed clinical evaluation of the rSAG1-loaded RDT in 182 cat sera (55 household and 127 stray cats). The kit showed 0.88 of kappa value comparing with a commercialized ELISA kit, which indicated a significant correlation between rSAG1-loaded RDT and the ELISA kit. The overall sensitivity and specificity of the RDT were 100% (23/23) and 99.4% (158/159), respectively. The rSAG1-loaded RDT is rapid, easy to use, and highly accurate. Thus, it would be a suitable diagnostic tool for rapid detection of antibodies in T. gondii-infected cats under field conditions.

Abordagem diagnóstica e terapêutica da toxoplasmose em gestantes e as repercussões no recém-nascido

OBJETIVO:Avaliar a abordagem diagnóstica e terapêutica da toxoplasmose de gestantes que apresentaram IgM positiva para a doença e o acompanhamento de seus filhos em um hospital público no Rio de Janeiro, RJ. MÉTODOS: Estudo transversal retrospectivo de 2003 a 2006, realizado por meio da análise dos prontuários de 98 gestantes com sorologia IgM positiva para toxoplasmose e seus filhos (99 crianças). O seguimento das crianças com e sem infecção congênita foram analisados, assim como a apresentação clínica daquelas com infecção congênita e os testes diagnósticos utilizados para identificar a infecção pelo Toxoplasma gondii durante a gestação. RESULTADOS: O diagnóstico sorológico foi realizado em 76 pacientes no segundo e terceiro trimestre gestacional. Em 36 gestantes, a determinação dos níveis séricos de IgM foi o único teste diagnóstico realizado para infecção pelo toxoplasma. Em 49 gestantes, os índices de IgM, pela técnica ELFA, foram baixos. O teste de avidez de IgG foi realizado em 62 gestantes e somente 13 o realizaram no primeiro trimestre gestacional. O tratamento específico para toxoplasmose foi empregado em 93 gestantes. A taxa de transmissão vertical foi de 4%. Manifestações clínicas de toxoplasmose congênita foram encontradas em todas as crianças infectadas. Todas as crianças não infectadas apresentaram declínio de IgG específica para toxoplasmose ao longo do acompanhamento ambulatorial; a idade média de IgG comprovadamente negativa nessas crianças foi de 5,4 meses. CONCLUSÕES: Os resultados sugerem que uma sorologia positiva para IgM, como um único marcador sorológico para detectar infecção recente, tem um valor limitado.

A prospective study of Toxoplasma-positive pregnant women in southern Brazil: a health alert

We evaluated anti-Toxoplasma gondii IgM-reactive pregnant women seen at a high-risk pregnancy outpatient clinic. From March 2005 to January 2008 in Paraná, Brazil, pregnant women seen by the Brazilian Public Health System, in any gestational period, who were anti-T. gondii IgM-positive, were followed. Clinical symptoms were noted, and tests performed including IgA, IgG avidity, ultrasonogram, and amniocentesis (PCR/inoculation in mice). Of 75 patients, 8 showed low, 3 intermediate and 31 high IgG avidity. Of those who underwent the avidity test, 31 (70.5%) were in the second trimester of pregnancy. Thirty-two (42.7%) pregnant women received specific treatment. Six received triple combination treatment; in three, tachyzoites were isolated, although only one was PCR-positive, showing changes in the cerebral sonogram, borderline IgA, and the Sabin tetrad. One fetus died, and one non-reactive IgM pregnant woman showed ocular recurrence. The municipality of residence, contact with cats during adulthood, and ingestion of unpasteurized milk were shown to be important risk factors. Congenital toxoplasmosis was observed in a pregnancy referred late for treatment. Follow-up of children born to mothers with diagnosed or suspected acute toxoplasmosis is crucial in the management of the changes that toxoplasmosis may cause.

Toxoplasmosis in pregnancy: determination of IgM, IgG and avidity in filter paper-embedded blood

OBJECTIVE

To detect immunoglobulin M (IgM) anti-Toxoplasma gondii antibodies and determine immunoglobulin G (IgG) titer and avidity in filter paper-embedded blood (FPEB) samples of pregnant women.

STUDY DESIGN

A total of 100 FPEB samples of pregnant women (30 positive and 70 negative) were analyzed for anti-T. gondii-specific IgM antibodies. Eleven and nine pairs of serum and FPEB samples were used to standardize IgG titration and avidity, respectively. Then, the correlation of avidity results was determined with 23 serum/FPEB pairs from IgG-positive cases.

RESULT

IgM detection in FPEB was 92% sensitive and 100% specific. The titration of IgG antibodies in FPEB correlated with that of serum (r >or=0.9). Significant difference in avidity between the acute and the undetermined/chronic cases was observed in both samples. As expected, no correlation was found between IgM levels and avidity.

CONCLUSION

The FPEB is useful to infer infection phase, and thus to speed clinical decisions in congenital toxoplasmosis management.

LDBio-Toxo II immunoglobulin G Western blot confirmatory test for anti-toxoplasma antibody detection

Tests commonly used for routine determination of anti-Toxoplasma gondii immunoglobulin G (IgG) antibodies show a high level of consistency. However, considerable variations between commercial screening tests are still observed in detecting antibodies present at low concentrations, leading to a number of discrepant and/or equivocal results. It is therefore important to use a reference test to confirm borderline results. In this study, we evaluated the use of a new qualitative test based on Western blot analysis--the LDBio-Toxo II IgG test--as a confirmatory test for at-risk patients. The study was performed retrospectively, using 569 serum samples with "low-positive" (2 to 32 international units) anti-Toxoplasma IgG levels from 375 patients. These samples were either sera collected during the routine screening of pregnant women, from patients with unrelated infections, or from immunocompromised patients or sequential sera taken from pregnant women with acquired Toxoplasma infection or from their newborns during follow-up. The LDBio-Toxo II IgG test was compared to several commercial tests commonly used for anti-Toxoplasma IgG screening. The Sabin-Feldman dye test was used as a reference test. In this study, the results of the LDBio-Toxo II IgG test appeared to be consistent with those of the dye test; the LDBio-Toxo II IgG test had a specificity of 100% and a sensitivity of 99.2%. Our findings suggest that the LDBio-Toxo II IgG test is a useful serological tool in cases in which the presence or absence of Toxoplasma antibodies needs to be reliably determined, for example, for the follow-up of pregnant women and their newborns or for subjects with immune deficiencies following human immunodeficiency virus infection, hematological malignancies, or transplantation.

Evaluation of Toxoplasma gondii immunoglobulin G (IgG) and IgM assays incorporating the newVidia analyzer system

The new Vidia system is a fully automated system based on chemiluminescence and antigen bound to magnetic microparticles, which allows a fast measurement of Toxoplasma gondii-specific immunoglobulin G (IgG) and IgM levels. The analytical performances of the Vidia Toxo IgG and IgM assays were compared with those of the automated Vidas, AxSYM, and Liaison Toxo IgG and IgM assays. The comparative evaluation was performed utilizing 204 frozen sera belonging to 166 subjects and 201 fresh sera collected from 198 subjects. For the Vidia Toxo IgG system, the sensitivities were 100% in both the retrospective and prospective studies, and specificities were 98.39% in the retrospective study and 100% in the prospective study, respectively. The sensitivities of the other three Toxo IgG assays were 100%, and the specificities ranged from 96.77% to 100%. For the Vidia Toxo IgM assay, the sensitivity and specificity were 100% in both the retrospective and prospective studies. The overall sensitivities and specificities of the other three Toxo IgM assays ranged from 80% to 100% and from 99.44% to 100%, respectively. In our study, the Vidia system revealed excellent sensitivity (100% for both IgG and IgM assays) and good specificity (99.25% for IgG and 100% for IgM assays).

Toxoplasma gondii infection in pregnancy: opportunities and pitfalls of serological diagnosis

Because of its life cycle, the recovery of Toxoplasma gondii from biological samples is often impracticable. Consequently, a serological diagnosis represents the first and the most widely used approach to defining the stage of infection. The detection of IgG, IgM, IgA, IgE and IgG avidity by different methods offers this opportunity. However, the results may be affected by difficulties in interpretation, as the same antibody pattern may have a different valency, contingent upon subjects and clinical settings, e.g., pregnant women vs. neonates, and treated vs. untreated patients. This review describes the various factors that should be taken into account when performing serological tests for T. gondii, as well as the pitfalls that may be encountered during the interpretative process.

Toxoplasma gondii: Expression pattern and detection of infection using full-length recombinant P35 antigen

A complete P35 surface antigen of Toxoplasma gondii was sequenced (GenBank ). Immunoblot found that it reacted specially with T. gondii acute infected sera, and the recombinant P35 signal was specific for P35 antigen. The P35-GST protein was used as antigen to detect 125 sera samples by double-sandwich ELISA. P35-IgM positive rate in a chronic infected group, a persistent IgM positive chronic group, a recently seroconvered group and an acute infected group were 4% (1 out of 25), 16% (4 out of 25), 88% (22 out of 25), and 100% (25 out of 25), respectively. The sensitivity and specificity of the recombinant full-length P35 antigen were 100 and 96%, respectively. The detailed expression patterns of P35 antigen were studied in 36 IgM and IgG positive sequential samples from 10 recently seroconvered patients. Results showed that the P35-IgM positive rate decreased as the time after the first seroconversion increased. P35-IgM positive samples in the first, second, third, fourth, and fifth month after the first seroconversion test were 90, 78, 57, 50, and 33%, respectively. P35-IgG positive samples in the first, second, third, fourth, fifth, sixth, and seventh month after the first seroconversion test were 70, 100, 100, 100, 67, 100, and 100%, respectively. All samples were P35-IgM negative after the fifth month, and P35-IgG negative after the seventh month from seroconversion. P35-IgM existed the shortest time and was a more specific marker for T. gondii acute infection than P35-IgG, IgM, and IgG to whole tachyzoites antigens.

New Vidas assay for Toxoplasma-specific IgG avidity: evaluation on 603 sera

After the development of the new version of the test Vidas Toxo IgG with antigens obtained from tachyzoites cultured on cells, a Vidas avidity test has been recently developed. The aim of this study was to assess the value of the determination of avidity on the new Vidas test. This avidity test was performed on 553 sera obtained from pregnant women whose dates of infection had been determined and on 50 sera obtained from immunosuppressed patients. In the group of infection occurring less than 4 months before sampling, the avidity index was <0.3 on 266 among 267 sera. In the group of infection occurring more than 15 months before sampling, the avidity index was >0.3 for 44/46 sera of pregnant women and for 47/47 sera of immunosuppressed patients. Thus, the new version of avidity test was helpful primarily to rule out that an infection had occurred within the prior 4 months.

Seroreactivity to and avidity for recombinant antigens in toxoplasmosis

To improve serodiagnostic methods for the diagnosis of acute toxoplasmosis during pregnancy, a new test system has been developed and evaluated based on the use of recombinant antigens. Five recombinant Toxoplasma gondii antigens (ROP1, MAG1, SAG1, GRA7, and GRA8) were cloned in Escherichia coli, purified, and applied directly onto nitrocellulose membranes in a line assay (recomLine Toxoplasma). A panel of 102 sera from 25 pregnant women with supposed recent toxoplasmosis and from two symptomatic children was compared to a panel of 71 sera from individuals with past infection. Both panels were analyzed using a recombinant line assay for immunoglobulin G (IgG), IgM, and IgA antibodies and a reference enzyme-linked immunosorbent assay. Within the IgM-positive samples, antibodies against ROP1 were predominant regardless of the infection state. In IgG analysis a characteristic antibody pattern was found for very recent infections. This pattern changed to a different one during the time course of infection: antibodies against GRA7 and GRA8 were characteristic for very early IgG, whereas antibodies against SAG1 and MAG1 appeared significantly later. These results were further confirmed by determination of the IgG antibody avidity for every single recombinant antigen. In the time course of infection, IgG antibodies against the early recognized antigens matured significantly earlier than those directed against the later antigens did. The IgA patterns did not give reliable information about the infection time points. The data revealed that the recombinant line assay provides valuable information on the actual state of infection, especially during the early infection time points.

European multicenter study of the LIAISON automated diagnostic system for determination of Toxoplasma gondii-specific immunoglobulin G (IgG) and IgM and the IgG avidity index

The LIAISON system is a fully automated system based on chemiluminescence and antigen bound to magnetic microparticles. The system allows fast and precise measurement of Toxoplasma-specific immunoglobulin G (IgG) and IgM antibody levels and measurement of the IgG avidity index even at low levels of Toxoplasma-specific IgG antibodies in a single step without manual interference. Seven European centers participated in a multicenter evaluation of the LIAISON system. The sensitivity and specificity of the LIAISON system compared to the Sabin-Feldman dye test were 99.3 and 96.8%, respectively. In a comparison of the LIAISON Toxoplasma-specific IgM assay with an immunosorbent agglutination assay, the LIAISON assay had a sensitivity of 96.7% and a specificity of 95.4%. The LIAISON IgG assay showed agreements of 91, 100, and 100% with the AXSYM IgG (Abbott), VIDAS IgG (bioMerieux), and Platelia IgG (Bio-Rad) assays, respectively. The LIAISON IgM assay showed agreements of 95% with the AXSYM IgM and Platelia IgM assays, 96% with the ISAGA IgM assay (bioMerieux), and 97% with the VIDAS IgM assay. The coefficient of correlation between the LIAISON system and the VIDAS Toxoplasma-specific IgG avidity index was 0.81. By use of the Toxoplasma-specific IgG avidity index assay with specific IgM-positive samples, the diagnosis of infection with Toxoplasma gondii in early pregnancy has been improved significantly. The LIAISON avidity assay is a valuable assay for the exclusion of recently acquired infection with T. gondii (less than 4 months) in pregnant women, and it decreases significantly the necessity for follow-up testing.

High yield expression and single-step purification of Toxoplasma gondii SAG1, GRA1, and GRA7 antigens in Escherichia coli

This report describes a simple, highly efficient and reproducible method for obtaining large quantities of highly pure recombinant Toxoplasma gondii antigens, which can be used for diagnostic application. The obtained T. gondii SAG1, GRA1, and GRA7 antigens (as fusion proteins), expressed in Escherichia coli, contained polyhistidine tags at the N- and C-ends that allowed single-step isolation by metal-affinity chromatography on Ni(2+)-IDA-Sepharose columns. The immunoreactivity of the recombinant antigens was tested in an enzyme-linked immunosorbent assay (ELISA) format for potential application in the serodiagnosis of T. gondii infection.

Prenatal diagnosis of congenital toxoplasmosis

Ninety-three pregnant women with Toxoplasma gondii seroconversion during pregnancy underwent prenatal diagnosis of fetal toxoplasmosis. The following tests were used: (1). amniocentesis for mouse inoculation (93 subjects), (2). amplification of T. gondii DNA by polymerase chain reaction (PCR) (79 subjects), and (3). cordocentesis for the detection of T. gondii-specific IgM antibodies (13 subjects). All patients had serial ultrasonographic scans to detect those fetuses with abnormalities that could be associated with congenital toxoplasmosis. Eighteen pregnancies (19.4%) had evidence of vertical transmission. A total of 11/18 (61.1%) had positive amniotic mouse inoculation test, while 10/12 (83.3%) had positive PCR results. The combination of both tests allowed the prenatal diagnosis in 17/18 infected fetuses (94.4%). All patients who underwent cordocentesis for the detection of T. gondii-specific IgM antibodies had negative results. However, in two of the above cases fetal toxoplasmosis was detected by amniotic fluid studies. In five of the infected fetuses there were abnormal ultrasonographic findings. All pregnancies with evidence of vertical transmission were terminated, whereas the remaining pregnancies proceeded normally to term. The present data showed that amniotic fluid studies, preferably PCR amplification of T. gondii DNA, are the best diagnostic tools for the detection of vertical transmission in pregnancies with seroconversion during pregnancy.

Ocular toxoplasmosis after the fifth decade

PURPOSE

To describe the clinical features in patients presenting with ocular toxoplasmosis after the fifth decade and to analyze laboratory findings in comparison to uveitis history and clinical data.

DESIGN

Prospective consecutive observational case series.

METHODS

A prospective clinical analysis of 27 consecutive patients older than 50 years of age with primary or recurrent ocular toxoplasmosis was performed during a period of 8 years. These cases account for 12% of all ocular toxoplasmosis cases irrespective of age indexed in our institution during the same period. Paired serum and aqueous humor samples were tested for anti-Toxoplasma gondii IgG, IgM, and IgA antibodies. The presence of T. gondii DNA in aqueous humor was determined by polymerase chain reaction followed by DNA hydridization method.

RESULTS

Although similar in age, two groups were distinguished clinically: 12 patients (44%) presented with usual forms of retinochoroiditis (mean +/- SD, 1.6 +/- 0.5 disk areas [DA] in size); 15 patients (56%) presented with atypical lesions, greater than 3 DA in size (mean +/- SD, 5.0 +/- 2.0 DA). The second group showed a higher rate of complications (P =.028) and a poorer visual outcome (P =.015). Twenty-four patients (89%) had intraocular IgG production, 17 (63%) had intraocular IgA production, 3 (11%) had intraocular IgM production, and 12 (44%) had a positive T. gondii DNA detection.

CONCLUSIONS

After the fifth decade, ocular toxoplasmosis remains an important cause of posterior uveitis. The combination of antibody detection by immunocapture tests with T. gondii DNA detection, both in aqueous humor, allowed the diagnosis of toxoplasmic infection in the atypical cases with large ocular lesions.

Dissecting the IgM antibody response during the acute and latent phase of toxoplasmosis

A major problem in anti-toxoplasma IgM serology is the occurrence of clinically non-relevant (CNR) IgM in sera of latently infected (LI) individuals. The susceptibility for CNR IgM of the Toxo ISAGA IgM, Platelia Toxo IgM and Vidas Toxo IgM assays was determined using sera of LI individuals with an IgM titer in the Abbott IMx Toxo IgM assay. The specificity of CNR-IgM and IgM antibodies in sera of acutely infected (AI) individuals was compared by immunoblotting.Seven/19 samples with CNR IgM antibodies were found positive in the ISAGA IgM, compared with 16/19 and 17/19 with the Vidas and Platelia Toxo IgM assays, respectively. In contrast, immunoblotting allowed a distinction between CNR IgM and AI IgM antibodies of the 30 sera studied.Clearly, IgM assays are susceptible to CNR IgM antibodies. In cases of doubt, immunoblotting is of value as confirmation method. Because CNR IgM antibodies are specific for toxoplasma, it will be difficult to improve IgM ELISAs in such a way that CNR IgM antibodies will not interfere with the analysis.

Recombinant antigens to detect Toxoplasma gondii-specific immunoglobulin G and immunoglobulin M in human sera by enzyme immunoassay

We have evaluated the diagnostic utility of eleven Toxoplasma gondii recombinant antigens (P22 [SAG2], P24 [GRA1], P25, P28 [GRA2], P29 [GRA7], P30 [SAG1], P35, P41 [GRA4], P54 [ROP2], P66 [ROP1], and P68) in immunoglobulin G (IgG) and IgM recombinant enzyme-linked immunosorbent assays (Rec-ELISAs). Following an initial evaluation, six recombinant antigens (P29, P30, P35, P54, P66, and P68) were tested in the IgG and IgM Rec-ELISAs with four groups of samples which span the toxoplasmosis disease spectrum (negative, chronic infection, acute infection, and recent seroconversion). Our results suggest that the combination of P29, P30, and P35 in an IgG Rec-ELISA and the combination of P29, P35, and P66 in an IgM Rec-ELISA can replace the tachyzoite antigen in IgG and IgM serologic tests, respectively. The relative sensitivity, specificity, and agreement for the IgG P29-P30-P35 Rec-ELISA were 98.4, 95.7, and 97.2%, respectively. The resolved sensitivity, specificity, and agreement for the IgM P29-P35-P66 Rec-ELISA were 93.1, 95.0, and 94. 5%, respectively. Relative to the tachyzoite-based immunocapture IgM assay, the IgM P29-P35-P66 Rec-ELISA detects fewer samples that contain IgG antibodies with elevated avidity from individuals with an acute toxoplasmosis.

Diagnosis of congenital toxoplasmosis in the neonatal period: A multicenter evaluation

OBJECTIVE

To evaluate different laboratory tests used to diagnose congenital toxoplasmosis in the neonatal period.

STUDY DESIGN

A retrospective multicenter study of 294 pregnant women who experienced seroconversion for Toxoplasma gondii and subsequently delivered live-born infants. Fetal infection was assessed via specific IgM and IgA antibodies (cord and neonatal blood) and detection of T gondii in placenta and cord blood by mouse inoculation.

RESULTS

Ninety-three (32%) of the 294 infants were congenitally infected. The sensitivity of IgA in cord blood and in neonatal blood was 64% and 66%; the sensitivity of IgM was 41% and 42%, respectively. Mouse inoculation of the placenta and cord blood had sensitivities of 45% and 16%. Positive results of the serologic tests in congenitally infected children correlated significantly with the gestational age at the time of maternal infection but was not significantly influenced by the administration of specific antiparasitic treatment during pregnancy.

CONCLUSION

Specific T gondii IgA antibody is a more sensitive test than IgM for detecting congenital toxoplasmosis in the neonatal period. The overall specificity is better for serologic tests performed on neonatal blood than for those on cord blood. Neonatal screening with IgM or IgA antibodies will not detect the majority of children with congenital toxoplasmosis when the maternal infection occurred before the 20th week of pregnancy.

Prenatal diagnosis of congenital toxoplasmosis: a multicenter evaluation of different diagnostic parameters

OBJECTIVE

Our purpose was to evaluate different methods of diagnosing congenital toxoplasmosis prenatally by amniocentesis and cordocentesis.

STUDY DESIGN

In a retrospective multicenter study, we investigated consecutive women who had seroconversion for Toxoplasma gondii during pregnancy and who underwent either amniocentesis or cordocentesis or both to obtain a prenatal diagnosis of fetal toxoplasmosis. Data were obtained from 122 patients recruited in 6 different European Toxoplasma reference centers. Infants born to these mothers were followed up until 1 year of age to confirm or exclude congenital toxoplasmosis. Sensitivity, specificity, positive predictive value, and negative predictive value were measured for the following parameters: (1) detection of the parasite in amniotic fluid by mouse inoculation, (2) detection of the parasite in amniotic fluid by in vitro cell culture, (3) detection of Toxoplasma deoxyribonucleic acid in amniotic fluid by a polymerase chain reaction assay, (4) detection of the parasite in fetal blood by mouse inoculation, (5) detection of specific immunoglobulin M antibodies in fetal blood, and (6) detection of specific immunoglobulin A antibodies in fetal blood.

RESULTS

The polymerase chain reaction test performed on amniotic fluid had the highest level of sensitivity (81%) and also a high level of specificity (96%). The combination of the polymerase chain reaction test and mouse inoculation of amniotic fluid increased sensitivity to 91%. The sensitivity of immunoglobulins M and A in fetal blood was 47% and 38%, respectively. In congenitally infected fetuses a negative correlation was observed between positive serologic parameters and gestational age at the time of maternal infection and at prenatal diagnosis.

CONCLUSION

Congenital toxoplasmosis is best predicted by prenatal examination with the combination of T gondii polymerase chain reaction and mouse inoculation of amniotic fluid. The role of cordocentesis in the diagnosis of congenital toxoplasmosis is limited.