IgA antibody response during acquired and congenital toxoplasmosis.

Toxoplasma gondii specific IgA and IgM antibodies were quantitated by an antibody capture agglutination assay in 260 patients with acquired toxoplasmosis and from 94 fetuses suspected of congenital toxoplasmosis and 30 infected children. In acquired toxoplasmosis, IgA antibodies to T gondii were found in 95% of the cases. In congenital toxoplasmosis IgA antibodies were more frequently detected (75%) in cord blood than IgM antibodies (61%). They persisted after birth, in some cases for up to 24 months. IgA antibodies were also detected in fetuses whose mothers had toxoplasmosis during their pregnancy. In infected fetuses IgM and IgA antibodies were detected in fetal blood as early as week 24 of pregnancy. Detection of IgA T gondii antibodies may be useful for the diagnosis of some recently acquired infection and for the diagnosis and follow up of the infection in the fetus and neonate.     

Role of specific immunoglobulin E in diagnosis of acute toxoplasma infection and toxoplasmosis.

Toxoplasma immunoglobulin E (IgE) antibodies were evaluated in an immunosorbent agglutination assay (ISAGA) and an enzyme-linked immunosorbent assay (ELISA) to determine their usefulness in the diagnosis of acute infection with Toxoplasma gondii. IgE antibodies were not detected in serum specimens from otherwise seronegative individuals, individuals with chronic toxoplasma infection, or infants without congenital toxoplasmosis. In contrast, they were detected in pregnant women who seroconverted during gestation (100% by ELISA, 63% by ISAGA), patients with toxoplasmic lymphadenopathy (96% by ELISA, 88% by ISAGA), infants with signs of congenital toxoplasmosis which prompted serologic testing in the postnatal period (92% by ELISA, 67% by ISAGA), children and adults with toxoplasmic chorioretinitis (36% by ELISA, 18% by ISAGA), and adult patients with AIDS and toxoplasmic encephalitis (33% by ELISA, 25% by ISAGA). In many of the serum specimens, the titer of IgE antibodies detected by the ISAGA were close to or at the positive cutoff value. The duration of detectable IgE antibodies in patients with acute infections varied considerably among individuals but showed a trend toward a briefer duration by the ISAGA than by the ELISA. These results reveal that recrudescence of IgE antibodies in patients with reactivated chronic infection (toxoplasmic chorioretinitis and toxoplasmic encephalitis) may be useful diagnostically and that demonstration of toxoplasma IgE antibodies is a useful adjunct to currently available serologic tests for the diagnosis of acute toxoplasma infection and toxoplasmosis.     

Detection of specific immunoglobulin E in patients with toxoplasmosis.

An immunocapture assay was developed to detect Toxoplasma gondii-specific immunoglobulin E (IgE) in sera from adults with acute acquired infection or reactivation and from babies with congenital toxoplasmosis. The components of this assay were monoclonal antibody to human IgE, samples from patients, and T. gondii tachyzoites treated with Formalin. When T. gondii-specific IgE antibodies were present, visually detectable agglutination occurred. Sera, umbilical cord blood, fetal blood, cerebrospinal fluid, and amniotic fluid were tested by this method. Specific IgE antibodies were detected in sera from 25 (86%) of 29 adults who developed specific IgG antibody during pregnancy or had specific IgA and IgM antibodies. Specific IgE was present early during infection, at the time that IgM antibodies were present, and slightly preceding the presence of specific IgA antibodies. In 23 patients tested serially, IgE antibodies never persisted for longer than 4 months. No nonspecific anti-T. gondii IgE was detected in sera from uninfected individuals. Maternal IgE antibodies did not cross the placenta. In sera of patients with congenital toxoplasmosis, specific IgE antibodies were found at birth, during the first year of life, and during immunologic recrudescence following discontinuation of pyrimethamine-sulfonamide therapy. The IgE immunocapture assay is simple to perform. It is especially useful for determining when T. gondii was acquired by recently infected pregnant women.     

Antigenaemia and antibody response to Toxoplasma gondii in human immunodeficiency virus-infected patients

Toxoplasma encephalitis in immunocompromised patients results from reactivation of previously acquired (latent) infection. The aim of the study is to assess the antigenaemia and antibody response to Toxoplasma gondii in human immunodeficiency virus (HIV)-infected patients to determine the best marker for early diagnosis of toxoplasmosis in such patients. Indirect enzyme-linked immunosorbent assay (ELISA) for detection of IgG, IgM and IgA anti-toxoplasma antibodies and double-sandwich ELISA for toxoplasma antigen is carried out in serum samples collected from 100 HIV seropositive patients and 75 controls. Toxoplasma-specific IgG, IgM and IgA antibody response and antigenaemia were detected in 12%, 6%, 7% and 14% of HIV-infected patients, respectively. On retrospective analysis of 14 patients with antigenaemia only one had central nervous system (CNS) symptoms attributable to toxoplasma infection. In this patient, the CD4+ cell count was below 50/microL and none of the specific immunoglobulin isotype responses could be detected. The patient showed clinical improvement following specific chemotherapy for toxoplasmosis. In 25 HIV-negative and anti-toxoplasma IgG antibody-positive controls, IgM was detected in two (8%), IgA in five (20%) and antigenaemia in 10 (40%), while 50 HIV seronegative healthy controls were negative for both antigen and antibody responses. The study indicates that detection of toxoplasma antigen in addition to IgG antibody response may prove to be a useful indicator in the early diagnosis of reactivated toxoplasmosis in HIV/AIDS patients.     

Immunoblot analysis of Toxoplasma gondii antigens by human immunoglobulins G, M, and A antibodies at different stages of infection.

The Toxoplasma gondii antigenic components eliciting the immunoglobulin G (IgG), IgM, and IgA antibody responses were studied by using follow-up sera from a laboratory worker who developed an acute glandular toxoplasmosis after an accidental infection with the protozoa. IgG toxoplasma antibodies reacted with multiple components over a wide molecular weight range from 6,000 to 150,000. In contrast, IgM toxoplasma antibodies reacted predominantly with polypeptides of 6, 25, and 35 kilodaltons, which might be useful in new diagnostic procedures. The general pattern of antigenic components in the IgA toxoplasma antibody response closely resembled that in the IgM response, even though some characteristic features were constantly observed. The possibility that the restricted IgM and IgA antibody responses relate to the pathogenetic events in human toxoplasmosis is considered.     

Platelia-Toxo IgA, a new kit for early diagnosis of congenital toxoplasmosis by detection of anti-P30 immunoglobulin A antibodies.

With the aim of achieving earlier diagnosis of congenital toxoplasmosis, anti-P30 immunoglobulin A (IgA) antibodies were assayed by using a Platelia-Toxo IgA kit with samples from 72 children born to mothers who seroconverted during pregnancy. A total of 148 serum samples and 1 cerebrospinal fluid samples were from 23 congenitally infected children (2 serum samples were collected from fetuses), and 74 serum samples were from 49 uninfected children. Among the 23 infected children, anti-P30 IgA antibodies were present in all infants either at birth or in the following weeks, whereas anti-P30 IgM antibodies were present in 13 from the 23 infected children either at birth or in the following weeks. Serum samples collected in utero from two infected children were also tested. One of these samples was positive for both anti-P30 IgA and anti-P30 IgM antibodies, whereas both children were negative at birth for these antibodies. Neither anti-P30 IgA nor anti-P30 IgM antibodies were detected in 47 of 49 uninfected children. These results suggest that detection of anti-P30 IgA antibodies by the Platelia-Toxo IgA kit is a very effective method for early diagnosis of congenital toxoplasma infection.     

Do IgA,IgE, and IgG avidity tests have any value in the diagnosis of toxoplasma infection in pregnancy?

AIM: To determine the value of tests for specific IgA, IgE, and IgG avidity in diagnosing Toxoplasma gondii infection during pregnancy. METHODS: In a retrospective study, current serological tests (dye test and three IgM assays with different sensitivities) were compared with immunosorbent agglutination assays (ISAGA) for specific IgA and IgE and an IgG avidity enzyme linked immunosorbent assay (ELISA). Patient group 1 comprised six women with definite or probable infection during pregnancy determined by congenital toxoplasmosis or laboratory results. Group 2 comprised seven women infected during or before 11 pregnancies (two consecutive pregnancies in two patients and three in a third). RESULTS: One patient in group 1 seroconverted during pregnancy. IgA ISAGA and avidity confirmed acute infection when confirmatory IgM ELISA remained negative. In five of six patients from group 1, IgA and IgE ISAGA and avidity confirmed acute infection. In group 2, the dye test titre was raised in seven of 11 pregnancies (six of seven patients). Specific IgM and IgA were positive during all 11 pregnancies. IgE ISAGA was positive in only four of 11 pregnancies (three of seven patients), but negative results in the remainder may exclude acute infection. High avidity antibodies indicative of past infection were found in four of 11 pregnancies (two of seven patients). CONCLUSIONS: Each test improved diagnosis or timing of infection but no single test was ideal. The IgA ISAGA was sensitive and detected seroconversion. Positive IgE ISAGA and low avidity both confirmed infection, whereas negative IgE may exclude acute infection. High avidity diagnosed past infection but persistence of low avidity reduced its value to differentiate acute and past infection. Further studies with larger patient groups are needed to determine the optimum diagnostic strategy. These techniques are valuable in complementing existing tests.     

Value of specific immunoglobulin a detection by two immunocapture assays in the diagnosis of toxoplasmosis

The diagnosis ofToxoplasma gondii infection is currently based on immunological tests, but tests for IgG and IgM antibodies alone are often insufficient to assess the risk of active disease, especially during pregnancy and in immunodeficient subjects. The supplementary diagnostic value of testing for antitoxoplasmic IgA in cases of acute, chronic, congenital and reactivated toxoplasmosis, relative to classical immunological tests, was evaluated using two immunocapture tests, one based on tachyzoite agglutination and the other on an immunoenzymatic complex recognizing the membrane protein P30 ofToxoplasma gondii. A total of 4,541 sera from 395 uninfected subjects, 468 immunized subjects with chronic infection, 117 subjects with acute infection and 403 children, 103 of whom had congenital toxoplasmosis, was tested. Specific IgA tests were negative in the nonimmune population, but tests for this immunoglobulin subtype became positive very rapidly during primary infection, and IgA disappeared more rapidly than IgM. In the children infected in utero, specific IgA was detected more frequently than IgM. In contrast, in a population of HIV-seropositive subjects with clinical toxoplasmosis, tests for IgA were poorly sensitive. The two tests for specific IgA produced similar results, except in the early stages of primary infection, in which immunoenzymatic testing for anti-P30 IgA was less sensitive than the agglutination method.     

Clinical value of specific immunoglobulin E detection by enzyme-linked immunosorbent assay in cases of acquired and congenital toxoplasmosis

The clinical value of immunoenzymatic (enzyme-linked immunosorbent assay) detection of anti-Toxoplasma immunoglobulin E (IgE) was assessed by studying 2,036 sera from 792 subjects, comprising seronegative controls and subjects with acute, active, reactivated, or congenital toxoplasmosis. Included were nonimmunized adults; pregnant women with recently acquired infection (acute toxoplasmosis); immunocompetent subjects with recently acquired severe infection (active toxoplasmosis) expressed as fever, adenopathies, splenomegaly, pneumonia, meningitis, or disseminated infection; subjects-some of them immunocompromised-whose previously moderate IgG antibody levels rose, suggesting a reactivation of quiescent toxoplasmosis; and infants born to seroconverted mothers and evaluated for diagnosis of congenital infection and therapeutic management. Specific IgE antibodies were never detected in seronegative subjects. They were present in 85.7% of asymptomatic seroconverters and in 100% of seroconverters with overt toxoplasmosis, following two different kinetics: in the former, the specific IgE titer generally presented a brief peak 2 to 3 months postinfection and then fell rapidly, whereas specific IgE persisted at a very high titer for several months in the latter. IgE emerged concomitantly with the increase in IgG during toxoplasmic reactivation. For neonatal diagnosis of congenital toxoplasmosis, IgE was less informative than IgM and IgA (sensitivities, 59.5, 64.3, and 76.2%, respectively) and had a specificity of 91.9%. Nevertheless, simultaneous measurement of the three isotypes at birth improved the diagnostic yield to 81% relative to the combination of IgA and IgM. Emergence of specific IgE during postnatal treatment for congenital toxoplasmosis is a sign of poor adherence or inadequate dosing.     

Specificity and usefulness of an IgE immunosorbent agglutination assay for toxoplasmosis.

AIMS--To develop an immunosorbent agglutination assay for the detection of Toxoplasma gondii IgE antibodies (IgE-ISAGA); to assess its specificity; and to determine the role of specific IgE in the diagnosis of current toxoplasma infection. METHODS--Rabbit antihuman IgE capture antibody was adsorbed onto microtitre plates and formaldehyde fixed tachyzoites were used to identify specific antibody. Specificity was assessed in 513 serum samples (blood donor, potentially interfering and difficult, elevated and low total IgE and myeloma). Serum samples (n = 108) from 65 patients with documented toxoplasmosis were tested, as were 26 serum samples from nine pregnant women positive for specific IgM and 30 from 20 HIV positive patients. RESULTS--IgE-ISAGA was highly specific with only three of 513 (0.58%) positive reactions amongst the control groups, one of which (0.19%) was regarded as a false positive. Elevated total IgE did not influence specific IgE results nor did the presence of abnormal immunoglobulin concentrations. Sixty (92.3%) patients with toxoplasma associated lymphadenopathy had specific IgE in one or more samples. Positive or borderline results were obtained in 68 of 77 (88.3%) serum samples taken up to four months after onset and were also detected for up to 11 months in 21 of 31 (67.7%) sera. Of the nine pregnant women with detectable specific IgM, specific IgE was absent in five (12 specimens). Specific IgE was also detected in 10 of 30 (33.3%) serum samples from the 20 HIV positive patients, which was similar to the number with specific IgM. Neither the specific IgE nor IgM tests could distinguish symptomatic from asymptomatic HIV positive patients. CONCLUSIONS--IgE-ISAGA is sensitive, specific, and easy to perform. Although results suggest that specific IgE may be less helpful than previously claimed, specific IgE has a useful role in the diagnosis of current toxoplasma infection when used in conjunction with other tests.     

Evaluation of serological markers for the immunodiagnosis of acute acquired toxoplasmosis

The detection of specific IgM antibodies has been the most frequently used serological marker for diagnosing recent toxoplasmosis. However, the persistence of specific IgM antibodies in some patients and the use of tests with a low specificity have complicated the interpretation of serological results when toxoplasmosis is suspected. The purpose of the present study was to determine the value of newer serological techniques in the diagnosis of acute acquired toxoplasmosis. Sixty-four sera, 31 from patients with Toxoplasma gondii infection and 33 from patients with latent infection, were tested. Anti-T. gondii IgA was measured by two antibody capture ELISA tests (Platelia Toxo IgA and ETI-TOXOK A) and an automated direct ELISA (IMx Toxo IgA); all three assays detected antibody levels compatible with a recent infection in sera from all 31 patients with acute toxoplasmosis. However, significant levels of IgA were also detected with high frequency by all three assays in sera from patients with latent infection. IgE antibodies detected by IgE immunosorbent agglutination assay (ISAGA) were present in 26 (84%) of 31 patients with acute toxoplasmosis and in sera from two subjects with latent infection taken >1 year after the beginning of the clinical symptoms of infection. Thirty (97%) of 31 patients with a recent T. gondii infection and 15 (45%) of 33 subjects with latent infection had an AC/HS pattern compatible with acute toxoplasmosis. The avidity of T. gondii IgG was evaluated by two methods. One method was based on the titration of each serum sample and calculation of the titres, in the absence and presence of urea, in relation to a defined cut-off value. In the other method, a single serum dilution was used and the absorbances of the reactions in the presence and absence of urea were compared. The titration method was more sensitive for diagnosing recent primary infection; all 31 sera from patients with acute toxoplasmosis had avidity indices compatible with acute toxoplasmosis by the titration method, whereas with the single dilution method, sera from four patients had equivocal results. In the 33 individuals with latent infection, similar results were obtained with the two avidity methods; only one serum sample had a non-compatible avidity value with the titration method. The results obtained in the present study show that the current serological markers used for diagnosing acute acquired toxoplasmosis have significant limitations. The data suggest that determination of the avidity of T. gondii-specific IgG by the titration method in patients with detectable IgM antibodies defines most accurately the stage of infection by T. gondii.     

Anti-P30 IgA antibodies as prenatal markers of congenital toxoplasma infection

This study extends a previous study and confirms that the detection of anti-P30 IgA antibodies is very helpful in the diagnosis of acute acquired or congenital toxoplasmosis. Moreover, we demonstrate that an anti-P30 IgA response can be mounted in the fetuses infected by Toxoplasma gondii during their intra-uterine life as early as week 23 of gestation. A double-sandwich ELISA described in our previous work was used to detect anti-P30 IgA antibodies in 1378 human serum samples collected from 551 patients, including 162 fetuses whose mothers had been infected by T. gondii during pregnancy, 46 congenitally infected and 90 uninfected newborns and 253 women suspected of having been infected during pregnancy, including the mothers of fetuses and newborns previously described. Anti-P30 IgA antibodies were detected in all cases of acute toxoplasmosis but in no case of chronic toxoplasmosis: in the majority of cases, the IgA antibody titre fell below cut-off in 3-9 months. Among the 46 congenitally infected newborns, anti-P30 IgA antibodies were detected in sera of 41 infected newborns (38 at birth, two in the first months of life, one in the seventh month of life), while anti-P30 IgM antibodies were detected in only 30 cases at birth and in one case during the first month of life. Among 162 fetuses, anti-P30 IgA response was observed in five infected fetuses, but was not detected in either 152 uninfected fetuses or in five fetuses considered as infected. The absence or presence of anti-P30 IgA antibodies in the fetus is discussed in relation to the date of maternal infection and collection of the fetal blood. It clearly appears from our study that the combined testing of both IgM and IgA in the fetus and the newborn is essential for a more efficient diagnosis of infection.     

Comparative immunoglobulin G antibody profiles between mother and child (CGMC test) for early diagnosis of congenital toxoplasmosis

Early diagnosis of congenital toxoplasmosis is rendered difficult when specific immunoglobulin M (IgM) and/or IgA antibodies are absent in the blood of the newborn infant. Since maternal IgG antibodies can cross the placenta, determination of IgG antibodies in newborn infants has hitherto not been used routinely for the diagnosis of congenital infection. The aim of this study was to assess the diagnostic usefulness of an immunoblot assay which compares the early IgG profiles between the mother and her child (comparative IgG profile between mother and child; CGMC test) directed against a total cell lysate of Toxoplasma gondii tachyzoites. Serum samples from 97 newborn infants at risk of toxoplasma infection were obtained from umbilical cord blood at birth or postnatally until 3 months of life and were directly compared with serum samples from the respective mothers. Congenital toxoplasmosis was diagnosed only when IgG-reactive protein bands that were present in any newborn serum samples were absent in the corresponding maternal serum sample. Congenital infection was defined by conventional serological assays when IgM and/or IgA antibodies were present in newborn infant blood or when IgG titers rose within the first 12 months or were persistently stable for more than 8 months. Using these criteria, congenital infection was definitely confirmed in 11 cases. Three additional cases were diagnosed based on indicative data. The CGMC test, which was performed without knowledge of the results of conventional serologal assays, had sensitivity and specificity of 82.4 and 93.0%, respectively, and positive and negative predictive values of 73.7 and 95.7%, respectively. When true positives and true negatives were considered, the comparative IgG profile had a ratio of 90.9% true results. The CGMC test thus is useful as an additional assay for the rapid diagnosis of congenital toxoplasmosis when paired serum samples from mother and child are available.     

Serological screening for antenatal toxoplasma infection in India

Purpose: Detection of infection caused by Toxoplasma gondii during pregnancy to prevent congenital infection. Materials and Methods: This study was carried out from January 2005 to 2006 in 300 pregnant women. Antitoxoplasma IgG, IgM, IgA antibody and IgG avidity were assessed using ELISA. Atleast two samples were taken atleast 3 weeks apart preferably one in each trimester. Result: Of these 300 pregnant women, anti toxoplasma IgG antibodies were detected in 46 (15.33%) cases, while 9 (3%) had positive anti toxoplasma IgM with IgA and /low IgG avidity antibodies suggestive of acute infection during or just before pregnancy. Conclusion: The results indicate that about 85% of female population of Chandigarh is susceptible to toxoplasma infection and thus should be specifically educated about prevention of this infection during pregnancy     

Performance of a Western Blot Assay to Compare Mother and Newborn Anti-Toxoplasma Antibodies for the Early Neonatal Diagnosis of Congenital Toxoplasmosis

 The aim of this study was to retrospectively evaluate the performance of a Western blot assay to compare mother and newborn anti-Toxoplasma gondii antibodies for the early neonatal diagnosis of congenital toxoplasmosis. Since specific anti-Toxoplasma IgM or IgA is detected inconstantly at birth in the neonate, the diagnosis of congenital toxoplasmosis is often delayed until 6–9 months, after IgG titers have been observed persistently. In this study, 81 paired samples from 60 mother/child pairs were tested for IgG and IgM patterns. All mothers had (or were strongly suspected to have) acquired toxoplasmosis during pregnancy. Specific IgM and IgA were simultaneously detected by immunocapture tests, and IgG was titrated. A serological and clinical follow-up of infants was conducted during the first year of life until the diagnosis of congenital toxoplasmosis could be either confirmed or ruled out. Seventeen of the 60 newborns were congenitally infected. Specific IgM or IgA was detected by immunocapture at birth in 76.5% and 70.6% of cord sera from infected neonates, respectively, with an equal specificity of 77.5%. Comparative Western blot allowed the detection of neosynthesized IgG and IgM in the cord blood of 50% and 78.6% of infected infants, respectively, with a specificity of 100%. The combination of IgA and IgM immunocapture tests, the analysis of IgG and IgM Western blot patterns, and the combination of both techniques allowed the detection of 94%, 94%, and 100% of cases within the first 3 months of life, respectively. In conclusion, Western blotting seems to be a useful complementary tool for the early postnatal diagnosis of congenital toxoplasmosis.     

Evaluation of a Commercial IgG/IgM Western Blot Assay for Early Postnatal Diagnosis of Congenital Toxoplasmosis

The aim of this study was to evaluate a commercial Western blot IgG/IgM assay for use in the early serological diagnosis of congenital toxoplasmosis. This assay compares the immunological profile of mother and infant and allows differentiation between passive transmitted maternal antibodies and newly synthesized antibodies of the infant within the first 3 months of life. Over a 6-year period (1995–2001), the sera from 169 mothers and their 175 offspring (6 had twins) were examined for specific anti-Toxoplasma gondii IgG, IgM and IgA antibodies with an enzyme-linked immunosorbent assay or an immunosorbent agglutination assay. All mothers had primary Toxoplasma infection during pregnancy. Serological and clinical follow-up of the infants during the first year of life confirmed 36 cases of congenital toxoplasmosis. In 139 cases, infection could be ruled out. Three hundred fifty-one paired samples from 175 mother-child pairs were tested retrospectively for IgG and IgM patterns by Toxoplasma Western blot IgG/IgM (LDBIO Diagnostics, France). The results of conventional serological analysis (immunosorbent agglutination assay or enzyme-linked immunosorbent assay) to detect IgM or IgA were compared with the results of the Toxoplasma Western blot IgG/IgM on samples obtained within the first 3 months of life. The performance of the combination of the two methods was also assessed. At birth, the sensitivity values of conventional serological analysis and the Toxoplasma Western blot were 52% and 67%, with specificity values being 99% and 96%, respectively. Combination of the Western blot and conventional serological analysis increased the sensitivity at birth to 78% and within the first 3 months of life to 85%. Overall, the combination of both methods detected 94% of congenital infections. Therefore, this commercial Western blot represents a useful tool for early postnatal diagnosis of congenital toxoplasmosis. Electronic Publication     

An enzyme-linked immuno-filtration assay used to compare infant and maternal antibody profiles in toxoplasmosis

Enzyme-linked immuno-filtration assay is carried out on a micropore membrane. This doubly analytical technique permits simultaneous study of antibody specificity by immunoprecipitation and characterisation of antibody isotypes by immuno-filtration with enzyme-labelled antibodies. Recognition of the same T. gondii antigenic constituent by IgG, IgA, IgM or IgE antibodies produces couplets (IgG-IgM; IgG-IgA) or triplets (IgG-IgM-IgA; IgG-IgM-IgE) which identify the functional fractions of the toxoplasmosis antigen. In acquired toxoplasmosis, the persistence of IgM antibody long after infestation puts in question the implication of recent infestation normally linked to detection of this isotype. For sera of comparable titres, comparison of immunological profiles by the method described demonstrates disparities in the composition of the specific antibody content as expressed in international units. Use of the same method to detect IgM antibodies or distinguish between transmitted maternal IgG and IgG antibodies synthesised by the foetus or neonate makes a diagnosis of congenital toxoplasmosis possible in 85% of cases during the first few days of life. With the method described the diagnosis may be made on average 5 months earlier than with classical techniques. In the course of surveillance for latent congenital toxoplasmosis, the appearance of IgM or IgE antibodies raises the possibility of complications (hydrocephalus, chorioretinitis). After cessation of treatment, a rise in IgG antibodies indicating persistence of infection is detected earlier by the present than by classical methods.     

Diagnostic significance of immunoglobulin M antibodies to Toxoplasma gondii detected after separation of immunoglobulin M from immunoglobulin G antibodies.

Failure to demonstrate immunoglobulin M (IgM) antibodies by indirect immunofluorescence (IgM-IFA) in sera from some patients with acute acquired toxoplasmosis has recently been attributed to an inhibitory effect of high titers of IgG antibodies in these sera (Pyndiah et al. J. Clin. Microbiol. 9:170-174, 1979). To confirm these findings and define their importance for diagnosis, we used gel filtration to separate IgM from IgG antibodies in a series of sera that were negative in the IgM-IFA test. A total of 68 sera were from patients with acquired toxoplasmosis, 13 were from uninfected adults, 13 were from infants with congenital toxoplasmosis, and 7 were from uninfected neonates. Of the 68 sera from patients with acquired toxoplasmosis, IgM preparations (from the separated sera) were positive in the IgM-IFA test in 36 (53%). There was a significant (P = 0.00003) association between high titers of IgM-IFA antibodies in the IgM preparations (corrected for dilution of IgM antibodies by the gel filtration procedure) and recent acquisition of infection. IgM antibodies were also detected in 5 (38%) of the IgM preparations of 13 sera from congenitally infected infants but not in any of the IgM preparations of sera from uninfected neonates. IgG antibodies to Toxoplasma gondii were shown to interfere with demonstration of IgM antibodies in the IgM-IFA test. Treatment of sera with protein A resulted in greater dilution of IgM antibodies and less efficient separation of IgM from IgG antibodies than did separation of sera by gel filtration. Treatment of sera with protein A did not result in increased detection of IgM antibodies to T. gondii. Testing of IgM preparations (obtained by gel filtration) resulted in a significant increase in sensitivity of the IgM-IFA test for the diagnosis of recently acquired and congenital toxoplasmosis.     

Evaluation of risk and diagnostic value of quantitative assays for anti-Toxoplasma gondii immunoglobulin A (IgA), IgE, and IgM and analytical study of specific IgG in immunodeficient patients.

To determine their prognostic and diagnostic values for toxoplasmosis in immunodepressed subjects, we assayed immunoglobulin A (IgA) and IgE antibodies by means of immunocapture (IC) tests, with revelation done by using a suspension of T. gondii (ICT). We also carried out a simultaneous analytical study of IgG antibodies on cellulose acetate membranes by using the comparative immunological profile method and an enzyme-linked immunofiltration assay (ELIFA). A total of 1,238 samples (serum, cerebrospinal fluid, and aqueous humor from 318 patients) were tested. IgA and IgE antibodies were detected in all heart, kidney, and liver transplant recipients with clinical manifestations of toxoplasmosis; IgA was detected in the aqueous humor of a patient with chorioretinitis. In patients with AIDS-related toxoplasmosis, including the cerebral form, IgA and IgE antibodies or a significant modification of ELIFA IgG values were observed in 38, 19, and 25% of patients, respectively. IgM was detected by ICT only in 12% of patients and aided the diagnosis in 1 of 71 patients. IC tests for specific IgA and IgE alone and combined with ELIFA were positive in 39 and 46% of patients who developed clinical toxoplasmosis, respectively. In a serial study of 16 patients in whom at least one of these three tests was positive, a significant immunological signal sometimes preceded clinical onset by 1, 6, and even 17 months. Similarly, in a group of human immunodeficiency virus-infected patients with evidence of previous exposure to T. gondii but no clinical manifestations, IgA, IgE, and IgA and/or IgE antibodies were detected in only 11, 4, and 12% of patients, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)     

Value of Prenatal Diagnosis and Early Postnatal Diagnosis of Congenital Toxoplasmosis: Retrospective Study of 110 Cases

We reviewed the files of 110 women with Toxoplasma seroconversion during pregnancy. Prenatal diagnosis was attempted for 94 women by amniotic fluid sampling. Toxoplasma gondii was detected by PCR, with or without tissue culture and mouse inoculation. The early neonatal diagnostic procedure included placental testing by PCR and/or mouse inoculation, cord blood serological testing, and comparison of maternal and newborn antibodies by Western blotting (WB). Serological follow-up of the infants was conducted during the first year of life or until the diagnosis of congenital toxoplasmosis (CT) could be ruled out. Congenital infection was diagnosed in 27 individuals (20 live births) in the prenatal and/or neonatal period. The sensitivity and specificity of prenatal diagnosis were 81 and 100%, respectively. Placental examination was positive for 66.7% of individuals with CT and was always negative for neonates without CT. Cord blood serology detected immunoglobulin M (IgM) and/or IgA in 80% of infected newborns, with respective specificities of 91.2 and 87.7%. By WB we detected bands on IgG and IgM blots recognized by the newborn serum but not by the maternal serum (neosynthesized IgG and/or IgM) for 88.2% of infected infants within the first 2 months of life with a specificity of 100%. Early postnatal diagnosis was negative for 2 of the 20 neonates with CT. Both of these newborns had a negative prenatal diagnosis and were asymptomatic, suggesting a very low parasite load. In conclusion, despite the use of advanced methods, some cases of congenital toxoplasmosis cannot be detected early, which underlines the importance of careful follow-up of newborns who are at risk.