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This study compared the performance of the LIAISON®XL system of immunoglobulin (Ig) G and IgM immunoassays for the diagnosis of Toxoplasma gondii, cytomegalovirus (CMV), and rubella virus infections with that of the ARCHITECT system. Patient serum samples, previously screened and clinically diagnosed with T. gondii, CMV or rubella, were used to compare LIAISON®XL and ARCHITECT IgG and IgM immunoassays. LIAISON®XL Toxo and CMV IgG avidity assays were also compared with equivalent ARCHITECT assays and reference methods. Overall agreement between the LIAISON®XL and ARCHITECT assays was 99% and 92% for the Toxo IgG and IgM assays, respectively, 98% and 96% for the CMV IgG and IgM assays, respectively, and 93% and 98% for the rubella virus IgG and IgM assays, respectively. LIAISON®XL IgG Toxo and CMV avidity assays showed high concordance with the VIDAS® Toxo IgG avidity assay and an in-house CMV avidity assay (reference methods), and faster IgG avidity maturation in a larger number of samples collected months after the primary infection compared with equivalent ARCHITECT assays. LIAISON®XL assays for detection of anti-T. gondii, CMV and rubella virus IgG and IgM are at least equal to the competitor assays on the ARCHITECT platform.

Transplantation activity is increasing, leading to a growing number of patients at risk for toxoplasmosis. We reviewed toxoplasmosis prevention practices, prevalence, and outcomes for hematopoietic stem cell transplant (HSCT) and solid organ transplant (SOT; heart, kidney, or liver) patients in Europe. We collected electronic data on the transplant population and prevention guidelines/regulations and clinical data on toxoplasmosis cases diagnosed during 2010-2014. Serologic pretransplant screening of allo-hematopoietic stem cell donors was performed in 80% of countries, screening of organ donors in 100%. SOT recipients were systematically screened in 6 countries. Targeted anti-Toxoplasma chemoprophylaxis was heterogeneous. A total of 87 toxoplasmosis cases were recorded (58 allo-HSCTs, 29 SOTs). The 6-month survival rate was lower among Toxoplasma-seropositive recipients and among allo-hematopoietic stem cell and liver recipients. Chemoprophylaxis improved outcomes for SOT recipients. Toxoplasmosis remains associated with high mortality rates among transplant recipients. Guidelines are urgently needed to standardize prophylactic regimens and optimize patient management.

Introduction: We report an unusual case of acute acquired toxoplasmosis (AAT) presenting as lymphadenopathy and recurrent seizures in an immunocompetent 15-year-old boy., Materials and Methods: The patient reported an 18-day vacation to Africa (Ethiopia), 39 days prior to the first seizure. Electroencephalogram (EEG) showed sporadic single-spike or sharp-wave paroxysms and the magnetic resonance imaging (RMI) of the brain was negative. The serology for T. gondii was compatible with an acute infection defined as positive for both toxoplasma-specific IgG and IgM and a low avidity (6 %), confirmed by a reference laboratory. The patient reported other two episodes of seizures, occurring 7 days apart. He was treated with pyrimethamine plus sulfadiazine and leucovorin for 4 weeks, with an improvement of lymphadenitis and normalization of EEG. After 5 months, new seizures were reported and a diagnosis of epilepsy was done. Toxoplasma polymerase chain reaction (PCR) of cerebrospinal fluid (CSF) and blood were negative. A treatment with valproic acid was started, obtaining control of the neurological disease., Conclusion: Awareness of this neurologic manifestation by clinicians is required, also in immunocompetent patients. The relationship between toxoplasmosis and recurrent seizure needs to be investigated by new studies.

The aim of the study was to evaluate the influence of treatment with spiramycin on the increase of immunoglobulin G (IgG) titers and IgG avidity indexes (AI) in pregnant women with seroconversion from the beginning of therapy until delivery and after delivery. This group was compared with adult patients with recently acquired untreated toxoplasmosis. One hundred four samples from 32 pregnant women with seroconversion for toxoplasmosis and/or very low IgG AI were followed from the beginning of therapy with spiramycin until delivery. Twenty-nine women were further followed some months after delivery and interruption of therapy. Thirty-eight samples from 16 untreated, nonpregnant patients were evaluated as the control group. The Toxoplasma gondii-specific IgG antibody and the T. gondii-specific IgG AI were significantly delayed in pregnant women receiving therapy compared to nonpregnant, untreated controls, and the findings were consistent with the results of assays from two different manufacturers. The T. gondii-specific IgG AI increased in pregnant women after they gave birth. Avidity maturation is delayed during pregnancy and treatment, and low-avidity antibodies in pregnant women within 3 to 4 months cannot be taken as a sign of infection.

Toxoplasmosis in pregnancy is usually subclinic or associated with non specific symptoms. Diagnosis and timing of infection are usually based on serological tests. In this short review we tried to summarize the serological patterns we can encounter and to discuss the interpretation of test results.

We evaluated the frequency of seroconversion for toxoplasmosis in seronegative recipients of thoracic solid organ transplants with seronegative or seropositive donors and the efficacy of chemoprophylaxis with pyrimethamine+sulfametopirazine. One hundred and sixty one patients seronegative for toxoplasmosis were followed-up at different intervals. Six patients out of 79 R-/D- and twelve out of 82 R-/D+ seroconverted after chemoprophylaxis interruption. There was no difference between matched and mismatched recipients as to the frequency of seroconversion which therefore could not be related to donor seropositivity. Seroconversions were almost asymptomatic. All positive recipients should be tested if symptoms of infection are present.

Isolates of Toxoplasma gondii, which is responsible for a wide range of clinical manifestations are grouped into three clonal lineages of different virulence in mice. However, it is not clear whether this genotypic pattern is associated with the clinical profile of the disease in humans nor is the geographical distribution of the genotypes known. This is mainly due to difficulties in obtaining parasitic DNA from patients. The available data are therefore limited and originate from acute or congenital infections or from animals. A non-invasive assay is needed to address issues of strain type, geographical distribution and severity of clinical toxoplasmosis. To serotype T. gondii strains, we have developed an enzyme-linked immunosorbent assay (ELISA) that uses polymorphic polypeptides specific to the three clonal lineages and derived from two dense granule antigens, GRA5 and GRA6. Two hundred and fifty-two sera from chronically infected pregnant women from three different European countries and Colombia were investigated. The analysis of genotype-specific antibody response showed a homogeneous type II distribution in the European samples compared with types I and III but no type II in the Colombian population. Our data concord with those obtained from the genotyping of other isolates from Europe and South America. We demonstrated that, despite some limitation due to antigen and/or antibody specificity, serotyping is a promising assay to investigate the relationship between type of strain and severity of the disease.

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.

A new complement fixation test for toxoplasmosis has been compared with the classical test indirect immunofluorescence test (IFAT) and indirect haemoagglutination test (IHAT). Neither false positive or negative results were obtained with LBCF-H100-TTE. Notably these values correlate well with IFA titers. Furthermore LBCF-H100-TTE shows the highest titers in acute cases and its time course is practically superimposable to IFAT. The differences obtained performing these different tests on the preferential detection of different antigen antibodies systems by these 3 tests are discussed.

We have devised a rapid and inexpensive gel filtration method to separate IgM fractions from small amounts of serum. These fractions have been titrated with IgM-IFAT and IgM-IHAT, and their titers have been compared with those obtained on whole serum. The results show that the separation of IgM from IgG allows detection of IgM antibodies in many cases of acquired toxoplasmosis, especially in cases of congenital toxoplasmosis. False positive results due to the presence of rheumatoid factors are also avoided. The IHA test performed on IgM fractions is constantly negative.

Mice were infected with a "cystogenic" strain of T. gondii and sera obtained at different times were tested using DT and IFAT (cell wall antibodies tests) and IHAT (performed with extractive cytoplasmic antigen). We found different kinetics of DT- and IFAT- versus IHAT-titers: IHAT is negative during the early phase of the experimental infection when DT and IgM-IFAT are already positive. Furthermore IgM antibodies were never found against cytoplasmic antigens by the IHAT method. At weekly intervals after the experimental infection a biological test was also performed using samples of different organs. We found that one week after the infection only the brain was constantly positive in the biological test. The antibody pattern was similar in every positive test irrespective of the source and size of the material used for the inoculum. These data suggest that the result of a biological test may be available earlier (already after 7 days) if a test for antibodies against cell wall antigens is performed on the IgM fraction of the mouse serum.

The present investigation has shown that the antibody titers obtained by IgG-IFA correlate well with 2-ME-DA (correlation coefficient 0.927, p less than 0.001). These results are obtained when the antibody titers are expressed as IU/ml. Buffer without 2-ME and purification of IgM fractions by simple gel-filtration method seem to be necessary conditions for detecting IgM antibodies by DA test in adult patients. Therefore the DA with these micromodifications has a specificity and sensitivity similar to those of IgG and IgM-IFA tests and would be convenient for laboratories that perform large scale surveys during pregnancy.

The present investigation has shown that antibodies titers obtained by IgM-IFA performed on pure IgM-fractions, obtained by gel-filtration method, correlate well with DS-IgM-ELISA. False negative IgM-IFA results that frequently occurs with sera having greater than or equal to 200 I.U./ml by IgG-IFA, were not observed with DS-IgM-ELISA: and the 98% of sera positive only after separation of IgM fraction with IgM-IFA, are also positive with DS-IgM-ELISA performed on whole serum.

An investigation carried out according to a predetermined serologic screening sought to evaluate the prevalence, level, and quality of fluorescent anti-Toxoplasma antibodies in a population sample of a certain district. The most important issues concern the risk of congenital toxoplasmosis for the above-mentioned subjects, the level of serotiter for expected risk, and the features of our screening protocol as regards thoroughness and the possibility of early diagnosis.

The specificity and sensibility of IgM-IFAT for diagnosis of acute acquired and congenital toxoplasmosis may increase after separation of IgM fractions by simple gel filtration method. In the presence of IFA-IgG titers greater than 250 IU/ml with Remington test less than 1/50, specific IgM antibodies to Toxoplasma gondii should be detected by separation. The separation of IgM seems a necessary step for detecting IgM antibodies by IgM-IFA in the newborn sera.

The use of a gel filtration method allowed us to obtain pure IgM fractions to be tested for specific Toxoplasma serology. The good correlation found in our series between IgM-IFAT and LBCF-H100-TTE performed on pure IgM fractions suggests that LBCF-H100-TTE may be another useful serological test for detection of IgM antibodies although false negative results might occur when LBCF-H100-TTE is performed on IgM fractions of cord sera.

The parasite Toxoplasma gondii can cause congenital toxoplasmosis following primary infection in a pregnant woman. It is therefore important to distinguish between recent and past infection when both T. gondii -specific IgM and IgG are detected in a single serum in pregnant women. Toxoplasma gondii -specific IgG avidity testing is an essential tool to help to date the infection. However, interpretation of its results can be complex. To review the benefits and limitations of T. gondii -specific avidity testing in pregnant women, to help practitioners to interpret the results and adapt the patient management. PubMed search with the keywords avidity, toxoplasmosis and Toxoplasma gondii for articles published from 1989 to 2019. Toxoplasma gondii -specific IgG avidity testing remains a key tool for dating a T. gondii infection in immunocompetent pregnant women. Several commercial assays are available and display comparable performances. A high avidity result obtained on a first-trimester serum sample is indicative of a past infection, which occurred before pregnancy. To date, a low avidity result must still be considered as non-informative to date the infection, although some authors suggest that very low avidity results are highly suggestive of recent infections depending on the assay. Interpretation of low or grey zone avidity results on a first-trimester serum sample, as well as any avidity result on a second-trimester or third-trimester serum sample, is more complex and requires recourse to expert toxoplasmosis laboratories. Although used for about 30 years, T. gondii -specific avidity testing has scarcely evolved. The same difficulties in interpretation have persisted over the years. Some authors have proposed additional thresholds to exclude an infection of <9 months, or in contrast to confirm a recent infection. Such thresholds would be of great interest to adapt management of pregnant women and avoid unnecessary treatment; however, they need confirmation and further studies. [ABSTRACT FROM AUTHOR]