Effect of testing for IgG avidity in the diagnosis of Toxoplasma gondii infection in pregnant women: experience in a US reference laboratory.
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The usefulness of testing for IgG avidity in association with Toxoplasma gondii was evaluated in a US reference laboratory. European investigators have reported that high-avidity IgG toxoplasma antibodies exclude acute infection in the preceding 3 months. In this US study, 125 serum samples taken from 125 pregnant women in the first trimester were chosen retrospectively, because either the IgM or differential agglutination (AC/HS) test in the Toxoplasma serologic profile suggested or was equivocal for a recently acquired infection. Of 93 (74.4%) serum samples with either positive or equivocal results in the IgM ELISA, 52 (55.9%) had high-avidity antibodies, which suggests that the infection probably was acquired before gestation. Of 87 (69.6%) serum samples with an acute or equivocal result in the AC/HS test, 35 (40.2%) had high-avidity antibodies. Forty women were given spiramycin, to prevent congenital transmission, and 7 (17.5%) had high-avidity antibodies. These findings highlight the value of testing a single serum sample obtained in the first trimester of pregnancy for IgG avidity. (+info)
Genotypic characterization of Toxoplasma gondii strains associated with human toxoplasmosis in Spain: direct analysis from clinical samples.
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Genetic analysis of the SAG2 locus was performed to determine the prevalence of the different genotypes of Toxoplasma gondii (strain types I, II, and III) associated with human toxoplasmosis in Spain. This determination was made directly from primary clinical samples, obviating the previous process of isolation in mice or cell culture. A total of 34 isolates of T. gondii, collected from immunocompromised patients and congenital infection cases, were analyzed. Restriction fragment length polymorphism in PCR-amplified SAG2 products was used to group strains into one of the three genotypes of T. gondii. Complete characterization of the SAG2 gene was successful in 76.5% of the cases, demonstrating the feasibility of direct genotype analysis from clinical samples of different origins. Strains of T. gondii type II were the most prevalent in immunocompromised patients, with 52% of cases, while strains of type I were present in 75% of the congenital infection cases. These data differ from previous reports that show type II strains to be mostly associated with all kinds of human toxoplasmosis. These differences might be an effect of selection in the process of culture and isolation of the samples performed by other researchers prior to strain characterization. (+info)
Cytologic detection of Toxoplasma gondii tachyzoites in cerebrospinal fluid.
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We reviewed our case records to see how often Toxoplasma gondii organisms were identified by cytologic evaluation of cerebrospinal fluid (CSF). During a 12-year period, 6,090 CSF specimens were examined, and 2 cases (0.03%) showed tachyzoites. Both patients were immunocompromised. One patient underwent lumbar and ventricular taps, and the other underwent only ventricular tap. Organisms were identified in the ventricular specimens but not in the lumbar sample. Both patients were treated, and subsequent ventricular CSF samples were negative. Toxoplasma gondii can be identified by cytologic examination of CSF. Our results confirm prior observations that in patients with obstructive hydrocephalus, tachyzoites are more likely to be found in ventricular rather than lumbar specimens. (+info)
Nramp1 is expressed in neurons and is associated with behavioural and immune responses to stress.
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The gene Nramp1 encoding the natural resistance-associated macrophage protein (Nramp1) influences susceptibility to intracellular infections and autoimmune diseases, and the humoral response to stress. Nramp1 functions as a proton/divalent cation antiporter in the membranes of late endosomes/lysosomes, regulating cytoplasmic iron levels in macrophages. The Drosophila homologue of Nramp1 is expressed in sensory neurons and macrophages, and influences taste behaviour directly through divalent cation transport. Here we demonstrate that murine Nramp1 is also expressed on neurons as well as microglial cells in the brain and influences the behavioural response to stress, hypothalamus-pituitary-adrenal (HPA) axis activation and mortality following Toxoplasma gondii infection in control and prestressed mice. We hypothesise that, although differences in HPA activation translate into differences in adrenal enlargement and basal circulating corticosterone levels, the primary influence of Nramp1 is at the level of the neuronal response to stress. These results provide new insight into the possible roles of divalent cation transporters of the Nramp gene family in regulating metal ion homeostasis in the brain and its pathological implications. (+info)
Infectivity of cysts of the ME-49 Toxoplasma gondii strain in bovine milk and homemade cheese.
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OBJECTIVE: Analyze the infectivity and storage resistance of cysts of the ME-49 strain of Toxoplasma gondii in artificially infected bovine milk and homemade fresh cheese. METHODS: Pasteurized bovine milk was infected with 10 cysts/ml of the ME-49 strain of T.gondii and inoculated in different groups of mice, immediately or after storage at 4 degrees C for 5, 10 and 20 days. Homemade fresh cheese was prepared with artificially infected milk, and also tested in groups of mice, using the same storage process. Infection was identified by the presence of cysts in the brain or serological testing in challenged mice after 5 weeks, confirmed by Western Blot and histology. RESULTS: The infectivity of cysts of the ME-49 strain of T.gondii was maintained in the milk even after storage for 20 days at refrigerator temperatures. Cysts were also able to survive the production process of homemade fresh cheese and storage for a period of 10 days in the same conditions. CONCLUSIONS: These data demonstrated that milk and dairy products could be an important source of T.gondii in human contamination, reinforcing the importance of milk pasteurization before any processing or ingestion. (+info)
Survey of obstetrician-gynecologists in the United States about toxoplasmosis.
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BACKGROUND: Although the incidence of toxoplasmosis is low in the United States, up to 6000 congenital cases occur annually. In September 1998, the Centers for Disease Control and Prevention held a conference about toxoplasmosis; participants recommended a survey of the toxoplasmosis-related knowledge and practices of obstetrician-gynecologists and the development of professional educational materials for them. METHODS: In the fall of 1999, surveys were mailed to a 2% random sample of American College of Obstetricians and Gynecologists (ACOG) members and to a demographically representative group of ACOG members known as the Collaborative Ambulatory Research Network (CARN). Responses were not significantly different for the random and CARN groups for most questions (p value shown when different). RESULTS: Among 768 US practicing ACOG members surveyed, 364 (47%) responded. Seven per cent (CARN 10%, random 5%) had diagnosed one or more case(s) of acute toxoplasmosis in the past year. Respondents were well-informed about how to prevent toxoplasmosis. However, only 12% (CARN 11%, random 12%) indicated that a positive Toxoplasma IgM test might be a false-positive result, and only 11% (CARN 14%, random 9%) were aware that the Food and Drug Administration sent an advisory to all ACOG members in 1997 stating that some Toxoplasma IgM test kits have high false-positive rates. Most of those surveyed (CARN 70%, random 59%; chi2 p < 0.05) were opposed to universal screening of pregnant women. CONCLUSIONS: Many US obstetrician-gynecologists will encounter acute toxoplasmosis during their careers, but they are frequently uncertain about interpretation of the laboratory tests for the disease. Most would not recommend universal screening of pregnant women. (+info)
Role of CD40 ligand signaling in defective type 1 cytokine response in human immunodeficiency virus infection.
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The pathogenesis of defective interleukin (IL)-12 and interferon (IFN)-gamma production in human immunodeficiency virus (HIV)-infected patients remains to be elucidated. This study investigated the possibility that perturbations in CD40 ligand signaling are involved in this defect. CD40 ligand trimer (CD40LT) stimulated peripheral blood mononuclear cell (PBMC) production of IL-12 in response to Toxoplasma gondii and cytomegalovirus (CMV). Regardless of the CD4 cell count, CD40LT restored IL-12 secretion in response to T. gondii in HIV-infected patients. In the presence of CD40LT, PBMC from both HIV-infected patients and control subjects produced high levels of IL-12 in response to CMV. CD40LT restored T. gondii- and CMV-triggered IFN-gamma secretion by T cells and PBMC from HIV-infected patients with a CD4 cell count >200 cells/microL. CD4 cells from HIV-infected patients, even those with a CD4 cell count >500 cells/microL, had defective CD40L induction after T cell stimulation mediated by antigen-presenting cells. Together, impaired CD40L induction is likely to contribute to defective IL-12 and IFN-gamma production in HIV infection. (+info)
Simple and efficient method for measuring anti-toxoplasma immunoglobulin antibodies in human sera using complement-mediated lysis of transgenic tachyzoites expressing beta-galactosidase.
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A simple and efficient method using transgenic Toxoplasma gondii tachyzoites expressing beta-galactosidase was developed for detection of specific antibodies against the parasite in sera of patients. The titers obtained with the new test were similar to those obtained with the Sabin-Feldman dye test run in parallel. Although significant changes in endpoint titers were not observed when sera drawn sequentially at 2- to 3-week intervals were tested with both procedures, apparent differences in antibody affinity were observed with the new test which were not perceptible with the Sabin-Feldman dye test. Like the Sabin-Feldman dye test, the new test is based on complement lysis of tachyzoites, but it is much easier to perform and the reaction is read colorimetrically instead of visually. (+info)