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PubMed1993

Prevalence of antibodies to Toxoplasma gondii in the Tel-Mond area.

Sera from 1,315 inhabitants of the Tel-Mond area were tested by the indirect immunofluorescent and Sabin Feldman tests for Toxoplasma antibodies. The overall prevalence of antibodies was 29.3%. Antibodies rose with age from 9.9% in the 1-4 year age-group up to 40.9% in the 45 age-group. There was no significant difference in prevalence of antibodies between the sexes. The prevalence of antibodies to Toxoplasma was lower in those born in Israel (21.2%) than in immigrants from Europe, America, Australia (49.4%), and Africa, Asia (40.8%) in the age groups of 20-45+. An extremely high prevalence of antibodies (41.5%) was found in Moshav Porat, a low socioeconomic settlement.

Adolescent↗
PubMed1993

Toxoplasma gondii induces a T-independent IFN-gamma response in natural killer cells that requires both adherent accessory cells and tumor necrosis factor-alpha.

Spleen cells from scid mice produce high levels of IFN-gamma when exposed to either live tachyzoites of Toxoplasma gondii or a soluble parasite extract. Small numbers of parasites are sufficient to stimulate this response, which is also induced by cell-free supernatants of cultured tachyzoites. The parasite molecules responsible for triggering IFN-gamma production are heat-labile but resistant to freezing and thawing. Depletion of NK cells or adherent cells from the splenocyte population abolishes the response. Moreover, cultured bone marrow-derived NK cells are stimulated by Toxoplasma to produce IFN-gamma, but only when supplemented with adherent peritoneal washout or thioglycollate-induced exudate cells. Supernatants of macrophages preincubated with T. gondii extract also induce IFN-gamma synthesis by cultured NK cells. Addition of neutralizing mAb against TNF-alpha abolishes the IFN-gamma response of scid spleen cells exposed to the parasite or of NK cells incubated with supernatants of adherent cells stimulated with T. gondii extract. Moreover, splenic adherent cells produce low levels of TNF-alpha in response to the parasite. Nevertheless, TNF-alpha alone is not sufficient to trigger IFN-gamma production from purified NK cell populations. These findings provide the first example of the stimulation of T-independent IFN-gamma production by a protozoan. The ability of T. gondii to trigger this pathway may underlie its induction of strong IFN-gamma-dependent nonspecific and specific cell-mediated immunity.

Animals↗
PubMed1993

[The clinical significance of culturing Toxoplasma gondii on blood and other organic media].

BACKGROUND: The aim of this study was to determine the value of the Toxoplasma gondii culture in blood and in other organic fluids in HIV positive and negative patients. METHODS: Retrospective analysis (October 1990-May 1992) was carried out including all patients with positive cultures for T. gondii admitted to the Hospital Central of Asturias. The parasite was identified by monoclonal antibodies against the tachyzoite membrane. All patients with positive cultures were treated with pyrimethamine and sulphadiazine. RESULTS: Three hundred two samples from 256 patients, seropositive and seronegative for HIV, were analyzed. Of the seropositive group 8/45 (18%) had positive cultures for T. gondii versus 9/211 (4.3%) of the seronegative group (p = 0.002). Of the 19 positive samples, 15 were from blood, 3 from bronchoalveolar lavage and one from the vitreous fluid. Four out of 9 patients (44%) with AIDS and encephalic toxoplasmosis (ET) had blood cultures positive for T. gondii. Another 4 patients with AIDS presented toxoplasmenia without visceral involvement. Of the 9 HIV seronegative patients (3 immunodepressed patients), 4 had pulmonary toxoplasmosis, one ocular toxoplasmosis, and other clinical forms of toxoplasmosis were seen in the remaining 4. All the patients evolved to cure except 2 cases coinfected by cytomegalovirus who died. CONCLUSIONS: The identification of Toxoplasma gondii may be performed by blood cultures in half of the patients with AIDS and encephalic toxoplasmosis and in an undetermined percentage of the other clinical forms both in immunocompetent and immunodepressed subjects. In addition, toxoplasmemia has been registered in AIDS patients preceding any other organic seating of the parasite. Early antitoxoplasma therapy may, therefore, be effective.

AIDS-Related Opportunistic Infections↗
PubMed1995

Sensitivity and specificity of various serologic tests for detection of Toxoplasma gondii infection in naturally infected sows.

The sensitivity and specificity of various serologic tests for antibodies to Toxoplasma gondii were compared in 1,000 naturally exposed sows, using isolation of viable T gondii as the definitive test. Serum samples obtained from heart blood of 1,000 sows from Iowa were examined for T gondii antibodies by use of the modified agglutination test (MAT), latex agglutination test (LAT), indirect hemagglutination test (IHAT), and ELISA. Toxoplasma gondii was isolated from 170 hearts of 1,000 sows by bioassays in mice and cats. The percentage of samples diagnosed as positive for each of the serologic tests was: MAT = 22.2% (titer > or = 1:20), IHAT = 6.4% (titer > or = 1:64), LAT = 10.4% (titer > or = 1:64), and ELISA = 24.1% (OD > 0.360). The sensitivity and specificity of these tests were calculated respectively to be: 82.9 and 90.29% for MAT, 29.4 and 98.3% for IHAT, 45.9 and 96.9% for LAT, and 72.9 and 85.9% for ELISA. The dye test was run at 1:20 dilution on only 893 sera because of bacterial contamination and presence of anticomplement substances. Dye test antibodies were found in 17.8% of the sera, and sensitivity and specificity were 54.4 and 90.8%, respectively. Thus, the MAT had the highest sensitivity among all serologic tests used.

Agglutination Tests↗
PubMed1977

[Methods for the preparation of a pure soluble antigen from Toxoplasma gondii].

In this study we report 4 methods for separating leucocytes from toxoplasma found in peritoneal exudate of infected mice. a) Passage through No: 26 needle, b) glass adherence, c) passage through glass wool, d) sonic vibration. Experiment showed that sonic vibration at 60 watt; 60 seconds was the best way to destroy selectively almost all leucocytes present in the preparation. In order to prepare a soluble antigen from clean toxoplasmas sonic vibration at 70 watt, 60 second was found sufficient to destroy all parasites present in the suspension. We suggest that this pure T. gondii antigen, may give more reliable results in passive hemagglutination, precipitation and complement fixation tests.

Animals↗
PubMed1996

Colchicine decreases the infection by Toxoplasma gondii in cultured glial cells.

Addition of colchicine (2.5 x 10(-8)-1.25 x 10(-6) M) to cultures of glial cells infected with Toxoplasma gondii decreased the number of parasites up to 80% (P < 0.05) in comparison with controls. Our results indicate that colchicine could interfere with the infectious, or replicative mechanisms, or both, of Toxoplasma and place it as a candidate in the search for additional antitoxoplasmic therapy for those cases where the parasitic load is massive. Further studies in vivo must be made to confirm this finding and provide support for therapeutic trials.

Animals↗
PubMed1996

Detection of Toxoplasma gondii in feline and canine biological samples by use of the polymerase chain reaction.

OBJECTIVE: To develop a polymerase chain reaction (PCR) technique to identify Toxoplasma gondii DNA in biological samples from cats and dogs. DESIGN: To artificially create samples that would mimic those acquired in a clinical setting from animals with naturally acquired toxoplasmosis. Using these samples, a PCR test to identify T gondii DNA was developed. SAMPLE POPULATION: Feline and canine aqueous humor, CSF, serum, and blood samples. PROCEDURE: Tachyzoites of several strains of T gondii grown in cell culture were added to feline and canine aqueous humor, CSF, serum, and blood samples. Protocols for identifying T gondii DNA by use of the PCR were developed. RESULTS: The DNA from as few as 10 tachyzoites of T gondii could be identified in feline and canine aqueous humor, CSF, and serum samples. One hundred tachyzoites could be identified in blood samples. CONCLUSIONS: Toxoplasma gondii can be identified in feline and canine biological samples by use of the PCR. CLINICAL RELEVANCE: Correlation of clinical disease to T gondii serum antibodies provides only a presumptive diagnosis of toxoplasmosis. Use of PCR to detect T gondii DNA in biological samples from cats and dogs may provide a sensitive tool for the antemortem diagnosis of toxoplasmosis and may be most beneficial when used in conjunction with serum antibody titers.

Animals↗
PubMedDate not supplied

Age influence in the natural resistance of white rat and mice to the protozoan Toxoplasma gondii.

Groups of 1, 5, 10, 15 and 30 day old rats (Sprague Dawley) and Wistar mice were infected per os with different inocula of Toxoplasma gondii oocysts from an avirulent strain. Infection pattern was followed by determination of survival time, tissue lesions, parasite presence and serology. Although all the animals survived the total experimental period (30 day), there were important differences between both rodents regarding to Toxoplasma natural resistance. Brain cysts, as well as tachyzoites in other organs were regularly present in mice but not in rats. On the other hand, most of the organs from mice presented characteristic T. gondii lesions, while in rats a normal tissues were observed, with the exception of an acute reaction found in the brain of a 15d old animal.

Age Factors↗
PubMed1996

IL-15 augments CD8+ T cell-mediated immunity against Toxoplasma gondii infection in mice.

Cytokines of the Th1 profile are important mediators of protective host immunity against Toxoplasma gondii infection in mice. In this study we describe the effect of the recently identified cytokine, IL-15, on prevention of murine infection with T. gondii. Administration of exogenous rIL-15 with soluble Toxoplasma lysate Ag (TLA) provides complete protection against a lethal parasite challenge, whereas treatment with either rIL-15 or TLA alone is not protective. Following immunization with TLA/rIL-15, there is a significant proliferation of splenocytes expressing the CD8+ phenotype in response to TLA. A significant rise in the level of serum IFN gamma was observed in vaccinated mice. Adoptive transfer of CD8+ T cells, but not CD4+ T cells, from TLA/rIL-15-vaccinated mice protects naive mice from a lethal parasite challenge. These CD8+ T cells exhibit enhanced CTL activity against target macrophages infected with T. gondii. Mice that have been immunized are protected against lethal parasite challenge for at least 1 mo postvaccination. These observations demonstrate that TLA when administered with exogenous rIL-15 generates toxoplasmacidal Ag-specific CD8+ T cells. These T cells proliferate upon exposure to parasite Ag, exhibit long term memory CTL against infected target cells, and may be involved in host immune memory to this parasite.

Adjuvants, Immunologic↗
PubMed1996

Inhibitory effect of interferon-gamma activated ovine umbilical vein endothelial cells on the intracellular replication of Toxoplasma gondii.

Toxoplasma gondii is an obligate intracellular parasite that is a major cause of abortion and neonatal mortality in sheep. In congenital toxoplasmosis, T gondii first invades the umbilical vein endothelial cells and are then disseminated throughout the fetus. Treatment of ovine umbilical vein endothelial cells with bovine recombinant gamma-interferon (IFN-gamma) blocked the growth of T gondii. Growth of the parasite was measured by 3H-uracil incorporation 18 h after the onset of the infection and by microscopic enumeration of parallel cultures. This assay revealed that when the cells were pretreated with IFN-gamma in concentrations ranging from 0.15-1,250 U/mL, a high degree of inhibition of T gondii replication was observed with the effect being dose-dependent. Maximum activation was achieved by incubating with 625 U/mL IFN-gamma and no activity was present at 0.15 U/mL. This technique could be of relevance as a first line of defense against congenital ovine Toxoplasma infection. Inhibition of T gondii replication is due to a different mechanism from that existing in mouse macrophages and human fibroblasts. L-Arginine-dependent production of reactive nitrogen and oxygen intermediates was not responsible for the inhibition of T gondii replication. Supplements of five amino acids were able to overcome the inhibition partially but significantly. The mechanism of the inhibition remains to be elucidated.

Amino Acids↗
PubMed1996

Evaluation of three immunoassays for detection of Toxoplasma-specific immunoglobulin G and M.

A time-resolved immunofluorometric assay of the IgG specific for Toxoplasma gondii has been compared with two commercial methods, one automated enzyme linked fluorescent assay (VIDAS) and one automated colorimetric enzyme immunoassay (BEIA). The coefficients of variation were 3.4% and 7.4% within-assay (n = 12), and 9.2% and 8.1% between-assay (n = 10) for two sera at low and high concentrations of specific IgG. The regression lines obtained with 96 samples were y = 1.04x + 2.1 and y = 0.98x - 1.1. We also compared a time-resolved capture fluoroimmunoassay for Toxoplasma-specific IgM with a commercial immunoenzymatic assay (BEIA TOXO-M). The sensitivity and specificity were 100%, calculated from assays of 78 samples.

Animals↗
PubMed1996

Primary and secondary Toxoplasma gondii infection in normal and feline immunodeficiency virus-infected cats.

Normal and asymptomatic feline immunodeficiency virus (FIV)-infected adult cats were inoculated orally with Toxoplasma gondii tissue cysts to assess differences in clinical disease, T. gondii serologic test results, hematologic results, and oocyst shedding. There was no difference between FIV-naive and FIV-infected cats in terms of clinical illness and duration of oocyst shedding following primary exposure. Both groups of cats developed significant decreases in neutrophil counts following primary inoculation with T. gondii; FIV-infected cats that were neutropenic prior to inoculation with T. gondii developed the most profound decreases in neutrophil numbers. Both FIV-naive and FIV-infected cats became lymphopenic during acute T. gondii infection; however, only FIV-naive cats developed lymphocytosis in the recovery stage. FIV-infected cats had lower total CD4+ and higher total CD8+ T-lymphocyte counts than FIV-naive cats prior to inoculation with T. gondii, but changes in these lymphocyte subsets were similar between groups of cats during the first several weeks after inoculation. Toxoplasma gondii infection had neither an ameliorating nor enhancing effect on T-lymphocyte subset abnormalities in FIV-infected cats during acute or chronic infection. Both groups of cats developed comparable levels of T. gondii-specific IgM and IgG antibodies and T. gondii antigen-specific lymphocyte blastogenic responses following primary inoculation. Both groups of cats were fed T. gondii tissue cysts 66 wk following primary exposure and both groups were solidly immune as evidenced by a lack of oocyst shedding and only minor changes in IgM but not IgG antibodies.

Animals↗
PubMed1996

Toxoplasma antibodies in clinically suspected cases of toxoplasmosis.

One hundred and seven cases, 35 males and 72 females aging from 3 months to 32 years old were divided into 4 groups: ocular, neurological, cases with abortion and cases having Down's syndrome. 47 apparently healthy individuals were taken as control. All were serologically tested for Toxoplasma antibodies using IFAT and ELSA for detection of IgG. The positive cases as well as cases below one year old were tested by ELISA IgM for the detection of acute or congenital toxoplasmosis. Toxoplasma antibodies (IgG) were found in 28 (26%) and 43 cases (40%) by IFAT and ELISA respectively. ELISA IgM was positive in 12 (20%) out of 60 serum samples. Two cases (11%) among 27 patients below one year old positive. Statistical significance was reported concerning the positive cases in the ocular group as well as patients with abortions. Results revealed that ELISA is more sensitive and specific than IFAT.

Adolescent↗
PubMed1996

[Prevalence of Toxoplasma gondii infections in groups of individuals in Rome and its environment].

This study was aimed out to point out the prevalence of Toxoplasma gondii infections in Roma and in the province. The results pointed out that the percentage of antibodies positivity has been 45% this prevalence was the same of the prevalence reported by other authors in Italy. The presence of a lot of women without anti-Toxoplasma gondii antibodies shows that is necessary to continue the control of the young women especially at the beginning of the pregnancy.

Animals↗
PubMed1996

Skeletal muscle pathology in mice experimentally infected with Toxoplasma gondii.

In two different groups of mice, the infection with Toxoplasma gondii was produced by intraperitoneal route, with 2 x 10(5) parasites (n = 8) and 14 x 10(5) parasites (n = 3). Five days after infection animals were killed to examine skeletal muscles by light and transmission electron microscopy. Severity of muscle alterations depended upon concentration of parasites. Parasite cysts were not identified in muscle sections. Ultrastructural features revealed different degrees of fibre atrophy, alterations in the sarcomeric structure and, in some cases, disorganization of contractile and sarcotubular systems. Changes in muscular capillaries included loss of the endothelial wall, occlusion of lumen and necrosis. Motor end-plates were abnormal and axonolysis was present. A mononuclear cell infiltrate consisted of macrophages, lymphocytes, mastocytes and eosinophils were observed. In this murine model it was demonstrated that the infection of non-immunocompromised hosts with Toxoplasma gondii produces an acute myositis.

Animals↗
PubMed1996

Seroprevalence of antibodies to Toxoplasma gondii, with particular reference to obstetric history of patients in Rawalpindi-Islamabad, Pakistan.

Six hundred and forty blood samples were obtained from Rawalpindi-Islamabad to determine the frequency of Toxoplasma gondii antibodies using indirect immunofluorescent antibody (IFA) test. Two hundred and forty samples were from suspected cases of Toxoplasmosis. Forty (17%) cases were positive for IgG antibody. Seven (3%) of these cases showed antibody titre greater than 1:320. Of 65 children tested, 8 (12.30%) were positive. Four (6%) children had a rising titre from 1:160 to 1:1025. Prevalence of Toxoplasma antibodies was correlated to mode of living, maternal obstetric history, their animal contact and age of the children.

Abortion, Spontaneous↗
PubMed1997

Serological and histopathological studies on toxoplasma Gondii among the workers and the slaughtered animals in Tanta Abattoir, Gharbia Governorate.

Toxoplasma gondii is one of the important zoonotic parasite of worldwide zoological and geographical distribution. In this paper, Toxoplasma antibodies were investigated among workers (21) and slaughtered animals (258) in Tanta abattoir. The indirect haemagglutination test (IHAT) was positive among workers (52.4%) at titers 1/64, 1/256, 1/512 and slaughtered animals (44.1%), at titers > 1:64. The indirect fluorescent antibody test (IFAT done for animals only) was positive (48.8%) at titers 1/40. Histopathological study on infected prescapular lymph nodes of the examined animals showed different clinical pictures, which coincided with the serological results. It was concluded that meat should not be consumed uncooked or undercooked.

Abattoirs↗
PubMed1995

Toxoplasma infection in healthy persons and in patients with HIV or ocular disease.

Toxoplasma infection is associated with acquired immune deficiency syndrome (AIDS), pregnancy, chorioretinitis, etc. Since the number of AIDS patients is increasing rapidly in Thailand and there are few reports about T. gondii immune status in this country. Toxoplasma-specific IgG and IgM antibodies (Ab) were determined in healthy persons and patients with different symptoms who were suspected of toxoplasmosis. Specific IgG Ab were detected in 3.2% of healthy persons, 12.5% of patients with ocular disease and in 42.5% in HIV positive patients. Only 3.1% of patients with ocular disease were positive for specific IgM Ab. No specific IgM Ab were found in the other samples studied.

AIDS-Related Opportunistic Infections↗