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PubMed1957

The treatment of experimental toxoplasmosis in rabbits.

Sulphadimidine alone is of little value in treating experimental toxoplasmosis in rabbits, because most rabbits acetylate the drug very rapidly. Within a short time of dosing such animals, there is little or none of the uncombined drug in the blood. In rabbits which do not acetylate sulphadimidine rapidly, relatively high concentrations of the free sulphonamide can be attained in the blood: in such animals, toxoplasmosis responds to treatment with sulphadimidine. Sulphathiazole is not acetylated so rapidly and is effective even in rabbits which acetylate sulphadimidine quickly. Pyrimethamine, even in doses as high as 50 mg. three times daily, is ineffective; dapsone is effective.

Animals↗
PubMed2001

HIV-2 infection with cerebral toxoplasmosis and lymphomatoid granulomatosis.

A Nigerian man had acute onset of headache and vertigo due to a cerebellar mass. A brain biopsy of the mass revealed toxoplasmosis despite repeated negative HIV-1 serology. The presence of an opportunistic infection and his country of origin raised the suspicion for HIV-2; this was confirmed by positive HIV-2 serology. Despite his preliminary pathological diagnosis, results of physiological magnetic resonance imaging (MRI) (perfusion MRI and proton magnetic resonance spectroscopy) were not typical for toxoplasmosis. The lesion showed a biochemical and perfusion pattern that was intermediate for infectious and neoplastic processes. Further neuropathology confirmed a secondary diagnosis of lymphomatoid granulomatosis.

AIDS-Related Opportunistic Infections↗
PubMed2004

Incidence and prevalence of toxoplasmosis in Indian pregnant women: a prospective study.

PROBLEM: Toxoplasmosis is a major cause of congenitally acquired infections causing high degree of morbidity and mortality in the newborns. METHODS OF STUDY: IgG avidity method was used to distinguish the recent and more than 4 months old infection in a prospective cohort study for the first time in India. One hundred and eighty pregnant women presented in their first 4 months of pregnancy were included in this study. Their sera were tested for anti-Toxoplasma gondii antibodies using direct agglutination test, immunoglobulin (Ig)G and IgM-enzyme-linked immunosorbent assay, IgM-immunosorbent agglutination assay and VIDAS-IgG avidity. RESULTS: Overall IgG seroprevalence rate of toxoplasmosis was 45%. Only seven women (3.3%) were found to have IgM antibodies and only two of these showed low IgG avidity indicating recent infection of <or=4 months duration. One woman aborted spontaneously at her fourth month of gestation. In remaining five women the recent infection could successfully be excluded by IgG avidity testing. All these women had uneventful pregnancy. CONCLUSIONS: This study indicated that all IgM antibody positive pregnant must be tested for IgG avidity to rule out recent primary infection.

Adult↗
PubMed1994

Brainstem toxoplasmosis in patients with acquired immunodeficiency syndrome.

Brainstem involvement by Toxoplasma gondii is probably more common than other opportunistic infections, although it has not received adequate attention. Identification of toxoplasmosis is essential, as this condition responds to treatment with a significant increase in life expectancy. During the past 4 years, 366 AIDS patients with central nervous system toxoplasmosis diagnosed by biopsy or improvement following empirical treatment were evaluated. Among them, 8 (7 men, 1 woman; aged 25-55 yr) presented with signs of brainstem dysfunction. Six patients presented with an oculomotor nerve palsy and contralateral hemiplegia; 1 had an additional ipsilateral rubral tremor. The seventh patient had complete external ophthalmoplegia and the eighth had Parinaud's syndrome. Computed tomography revealed enhancing lesions in the brainstem of all patients. Seven responded to treatment with pyrimethamine and sulfadiazine.

AIDS-Related Opportunistic Infections↗
PubMed1992

Activity of clarithromycin alone or in combination with other drugs for treatment of murine toxoplasmosis.

The activity of the macrolide antibiotic clarithromycin was examined alone or in combination with other drugs for the treatment of acute or chronic infections with Toxoplasma gondii in mice. A dose of 300 mg of clarithromycin per kg per day administered alone for 10 days, beginning 24 hours after infection, protected 10 to 30% of mice infected with lethal inocula of tachyzoites or tissue cysts of different strains of T. gondii, including some strains isolated from patients with both AIDS and toxoplasmosis. Although clarithromycin was protective, a wide variation in its activity against different strains was observed. Survival of infected mice was increased significantly by treatment with clarithromycin in combination with pyrimethamine or with sulfadiazine. Treatment of chronically infected mice with clarithromycin at 300 mg/kg/day administered alone for 8 weeks resulted in significant reduction in the numbers of T. gondii cysts in their brains. The combination of clarithromycin and minocycline resulted in an activity against T. gondii cysts that was significantly greater than the activity of clarithromycin or minocycline administered alone. These results indicate a role for clarithromycin in the treatment of human toxoplasmosis, particularly when this antibiotic is used in combination with other drugs with activity against T. gondii.

Acquired Immunodeficiency Syndrome↗
PubMed1997

Treatment with interleukin 12 in combination with atovaquone or clindamycin significantly increases survival of mice with acute toxoplasmosis.

The capacity of interleukin 12 (IL-12) to potentiate drugs in the treatment of murine toxoplasmosis was examined. IL-12 (100 ng/injection), atovaquone (10 mg/kg of body weight/day), or clindamycin (5 mg/kg/day) administered alone caused delayed time to death or minimal survival rates. In contrast, significant survival rates resulted when the same dose of IL-12 was used in combination the same doses of atovaquone (P=0.01) or clindamycin (P=0.001). Infected mice treated with IL-12 plus drug produced significantly higher levels of gamma interferon than controls. Although IL-12 was effective only when administered before infection, these results suggest that this cytokine may be a useful adjunct in the therapy of human toxoplasmosis in situations when cysts reactivate and tachyzoites start multiplying in immunocompromised patients.

Animals↗
PubMed1973

Automation of the indirect fluorescent-antibody test for toxoplasmosis.

The feasibility of automating the decision-making tasks of the medical technician in the determination of the results of the indirect fluorescent-antibody test for toxoplasmosis was investigated. Two approaches were studied: (i) macroscopic measurement of fluorescence from a large number of organisms (full-field illumination measurements), and (ii) microscopic measurements of fluorescence and morphology of individual parasites (pattern recognition). The macroscopic approach was studied utilizing an argon-ion laser in incident illumination with a Leitz Ortholux microscope and a phototube mounted so as to measure green fluorescence. Due to similar amounts of fluorescence from negative polar reactions and positive rim reactions, the macroscopic technique was concluded to be not feasible. The microscopic approach was studied utilizing a high resolution optical pattern recognition instrument. The results indicate that an object area measurement is sufficient to distinguish the presence of Toxoplasma gondii organisms from debris and overlapping organisms when studying the red fluorescence (due to Evans blue counterstain). Dark reactions were determined by the absence of green fluorescence. The differentiation of the rim and polar reactions was determined by the measurement of the ratio of green fluorescing area (due to fluorescein isothiocyanate) to red fluorescing area on the same organism. Clinically important titer information was also demonstrated to be obtainable. It was concluded that complete automation of the indirect fluorescent antibody test for toxoplasmosis is feasible with existing technology.

Computers↗
PubMed2005

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.

Animals↗
PubMed2002

Preconception seroconversion and maternal seronegativity at delivery do not rule out the risk of congenital toxoplasmosis.

We describe two unusual cases of congenital toxoplasmosis, one occurring after preconception maternal infection with cervical adenopathies and the other occurring after maternal infection at the very end of pregnancy with maternal seronegativity at delivery. These documented cases of congenital toxoplasmosis demonstrate the value of extending the serologic monitoring period during pregnancy, according to the individual clinical context.

Adult↗
PubMed1982

Toxoplasmosis in immunoglobulin M-suppressed mice.

Mice challenged with a pathogenic strain of Toxoplasma gondii develop fatal infections. However, if such mice are initially treated with sulfadiazine (SD), they develop immunity and survive with chronic infections. The role of antibody (Ab) in establishing protective immunity against acute parasitemias and in maintaining chronic infections was investigated using B-cell-deficient (immunoglobulin M-suppressed), T-cell-deficient (athymic), and normal BALB/c mice. All mice not receiving SD treatment rapidly died (mean 7.5 days) after infection, but the majority (80%) of intact mice developed immunity during SD treatment and survived for over 5 months with chronic toxoplasmosis. Athymic mice rapidly died (mean 6.0 days) after the removal of SD treatment. Although all SD-treated immunoglobulin M-suppressed mice eventually died, they lived considerably longer (18 to 83 days) in the complete absence of antitoxoplasma Ab than unprotected mice (7 to 9 days). Histopathological sections of liver, lung, brain, and other tissues showed that toxoplasma organisms gave rise to fatal lesions in all nonsurviving animals. The injection of Ab into acutely infected and athymic mice imparted no protection, but transfer of antitoxoplasma Ab (titer greater than 1:8,000) to immunoglobulin M-suppressed mice after SD treatment resulted in elimination of the parasites in 50% of the mice. Results of this study suggest that Ab may not be decisive in acute infections, but may be important in controlling long-term toxoplasmosis.

Animals↗
PubMed1993

Rat model of congenital toxoplasmosis: rate of transmission of three Toxoplasma gondii strains to fetuses and protective effect of a chronic infection.

The incidence of congenital toxoplasmosis in Fischer rats infected between the 8th and 12th days of pregnancy with three different strains of Toxoplasma gondii (RH, 76K, and Prugniaud) were 58.2, 35.2, and 62.8%, respectively. No infected fetuses were collected from rats previously infected with RH or Prugniaud strain parasites, even if the rats were reinfected during pregnancy. Since pups from chronically infected mothers are protected from congenital toxoplasmosis, rat infection could thus constitute a relevant model for immunological studies and vaccine design.

Animals↗
PubMed1994

Impairment of the cellular immune response in acute murine toxoplasmosis: regulation of interleukin 2 production and macrophage-mediated inhibitory effects.

Depression of the cellular immune response to Toxoplasma gondii has been reported in both mice and humans. The present study was undertaken to determine the kinetics and mechanism of the observed downregulation of interleukin 2 (IL-2) production during experimental murine toxoplasmosis. For these investigations, the cell-mediated immune response to the wild type (PTg) was compared with that to the less-virulent mutant parasite (PTgB), which is deficient in the major surface antigen, p30 (SAG-1). Spleen cells from infected A/J mice failed to proliferate in response to Toxoplasma antigens during the first week of infection. Both PTg- and PTgB-infected A/J mice exhibited a significant reduction in the concanavalin A (Con A)-induced lymphoproliferative response. Further, the response of splenocytes from mice infected with the wild-type parasite was significantly diminished compared with that of mice infected with PTgB. The lymphoproliferative response to Con A reached its nadir at day 7 and remained below control levels for at least 14 days postinfection. By day 21 postinfection, the response to Con A and to Toxoplasma antigens was restored to the level observed prior to day 7. Con A-stimulated culture supernatants of spleen cells from mice on day 7 postinfection contained significantly less IL-2 than normal mice. There was no significant difference in the numbers of binding sites or capacity of high-affinity IL-2 receptors between infected and normal mouse splenocytes as determined by Scatchard analysis. Exogenous IL-2 at different concentrations failed to restore the proliferative response of lymphocytes from infected mice to Con A. Adherent macrophages from 7-day-infected mice were able to suppress IL-2 production by normal splenocytes following stimulation with Con A. The inhibitory activity mediated by infected cells was reversed by the antibody to IL-10 but not transforming growth factor beta. There were insignificant levels of nitric oxide production in both infected and normal splenocytes. These results indicate that during acute murine toxoplasmosis, there is a well-defined period (day 7) during which both the T-cell mitogen and parasite antigen-associated lymphoproliferative response are reduced. Further, there is a reduction in the production of IL-2 and an increase in IL-10, which appear to mediate, in part, the observed downregulation of immunity to T. gondii.

Acute Disease↗
PubMed2000

Protective immunity against congenital toxoplasmosis with recombinant SAG1 protein in a guinea pig model.

Primary infection with Toxoplasma gondii during pregnancy can induce fetal pathology and abortion in both humans and animals. The present study describes the development of an experimental model of congenital toxoplasmosis in the guinea pig. In this animal model, we evaluated the protective effect of vaccination with a recombinant form of SAG1 against maternofetal transmission of tachyzoites. The presence of parasites in fetuses was determined by nested PCRs and by an in vivo readout after fetal brain homogenate injections in mice. The absence of parasites was demonstrated in 66 to 86% of fetuses derived from adult guinea pigs immunized with SAG1 and challenged with the mildly virulent T. gondii strain C56. In contrast, more than 80% of fetuses from mock-immunized guinea pigs were infected. The protection was not correlated with titers of antibody to SAG1. Our results indicated that this experimental model constitutes a relevant model for evaluation of vaccine candidates against congenital toxoplasmosis and that SAG1 elicits significant protection against maternofetal transmission.

Animals↗
PubMed2001

Immunological studies of chronic ocular toxoplasmosis: up-regulation of major histocompatibility complex class I and transforming growth factor beta and a protective role for interleukin-6.

A murine model was used to characterize the local immune and inflammatory response during ocular toxoplasmosis. Major histocompatibility complex (MHC) class I, normally expressed at low levels in immune-privileged sites such as the eye, was up-regulated during infection as determined by competitive reverse transcriptase (RT)-PCR and immunocytochemistry for both beta2-microglobulin and the MHC class I heavy chain. However, the eyes of chronically infected mice also had increased levels of mRNA transcripts for transforming growth factor beta, a cytokine associated with immune privilege and constitutively expressed in normal eyes. Transcripts for a number of inflammatory mediators, including interleukin-6 (IL-6), were increased during chronic infection. The role of IL-6 was further investigated by comparing disease progression and the development of the local immune response in wild-type (WT) and IL-6-deficient mice (IL-6(-/-) mice). Following infection, IL-6(-/-) mice developed more severe inflammation in the retina and vitreous humor compared with WT mice. This increased severity of disease was associated with reduced ocular IL-1alpha and increased tumor necrosis factor alpha mRNA production compared with WT mice. Moreover, the increased severity of disease in IL-6(-/-) mice correlated with increased eye parasite burden as determined by RT-PCR for the Toxoplasma gondii bradyzoite-specific LDH2 gene. These results demonstrate alterations to components of immune privilege as a result of ocular toxoplasmosis and a role for IL-6 in controlling parasite numbers and inflammation in the eye.

Animals↗
PubMed2003

The MIC3 gene of Toxoplasma gondii is a novel potent vaccine candidate against toxoplasmosis.

Infection with the intracellular protozoan parasite Toxoplasma gondii causes serious public health problems and is of great economic importance worldwide. The micronemal protein MIC3, which is a potent adhesin of T. gondii, could be a significant candidate vaccine against toxoplasmosis. In this study, all CBA/J mice intramuscularly vaccinated with a plasmid encoding the immature form of the MIC3 protein (pMIC3i) produced specific anti-MIC3 immunoglobulin G (IgG) antibodies, and their sera displayed high antibody titers. This response was increased by the coadministration of a plasmid encoding the granulocyte-macrophage colony-stimulating factor (pGM-CSF). Similarly, a specific and significant cellular immune response was obtained in mice immunized with pMIC3i, and this response was markedly enhanced by pGM-CSF coadministration. The cellular immune response was associated with the production of gamma interferon IFN-gamma and interleukin-2 (IL-2), indicating that this was a Th1-type response. This was confirmed by the production of large amounts of IgG2a. Mice immunized with pMIC3i displayed significant protection against an oral challenge with T. gondii 76K cysts, exhibiting fewer brain cysts than did the control mice. Coadministration of pGM-CSF enhanced this protection. In conclusion, this study describes the design of a potent DNA vaccine encoding the novel T. gondii target antigen, MIC3 protein, that elicits a strong specific immune response as well as providing effective protection against T. gondii infection. In the attempt to achieve complete protection against toxoplasmosis, MIC3 is a good candidate vaccine which could be combined with other relevant and previously described candidates, such as SAG1 and GRA4.

Adhesins, Bacterial↗
PubMed2003

Interleukin-10 and pathogenesis of murine ocular toxoplasmosis.

To understand the role of interleukin-10 (IL-10) in ocular toxoplasmosis, we compared C57BL/6 (B6) and BALB/c background mice lacking a functional IL-10 gene (IL-10(-/-)) and B6 transgenic mice expressing IL-10 under the control of the IL-2 promoter. Increased cellular infiltration and necrosis were observed in the eye tissue of IL-10(-/-) mice of both the B6 and BALB/c backgrounds with associated changes in the levels of cytokines in serum. In contrast, there was no evidence of necrosis in the eye tissue from IL-10 transgenic mice following parasite exposure. Our results demonstrate that IL-10 is important in the regulation of inflammation during acute ocular toxoplasmosis.

Animals↗
PubMed2005

Experimental ocular toxoplasmosis in genetically susceptible and resistant mice.

Genetic factors determining the pathogenesis and course of ocular toxoplasmosis are poorly understood. In this study, we explored the development of experimental ocular pathogenesis in genetically dissimilar mice infected with either the RH strain, the PLK strain, or the immunodominant surface antigen 1 (SAG1 [P30])-deficient mutant of the RH strain of Toxoplasma gondii. At 11 days postinfection, ocular infection of C57BL/6 mice with all of the strains of parasites resulted in severe inflammatory lesions and high numbers of parasites in eye tissue; less severe ocular lesions at earlier histopathology and prolonged survival were observed in this mouse strain infected with either the major surface antigen 1-deficient SAG1(-/-) strain or the less virulent PLK strain compared with RH infection. In contrast, both BALB/c and CBA/J mice had less severe lesions and low numbers of parasites in their eye tissue, and infection developed into the chronic stage in these mice. There were significantly higher serum levels of gamma interferon and tumor necrosis factor alpha in C57BL/6 mice than in BALB/c and CBA/J mice following ocular infection. These observations confirm earlier reports on systemic immunity to these parasites that the route of Toxoplasma infection markedly influences survival of mice. Our data indicate that genetic factors of the host as well as the parasite strain are critical in determining susceptibility to experimental ocular toxoplasmosis in murine models.

Animals↗
PubMed1985

Simple hemagglutination inhibition test for the diagnosis of toxoplasmosis.

A simple hemagglutination inhibition (HI) test for the serological diagnosis of toxoplasmosis has been developed and evaluated. A total of 84 human and 120 mouse serum samples were tested by the newly developed HI test and compared with an immunoglobulin G-indirect fluorescent antibody test. Statistical analysis of serum titers obtained by using the HI test and the immunoglobulin G-indirect fluorescent antibody test showed a correlation coefficient of 0.89. The diagnostic efficacy of HI when compared with the immunoglobulin G-indirect fluorescent antibody diagnostic test results was 96.43% for human sera and 100% for mouse sera. The unique hemagglutination antigen, derived from Toxoplasma gondii (Rh strain) exotoxin, spontaneously binds with mouse or rat erythrocytes, causing the hemagglutination reaction. In this study, 2, 4, or 8 hemagglutinating units of T. gondii exotoxin was used with Swiss/Webster mouse erythrocytes as an indicator for the HI assay. The results indicate that 8 hemagglutinating units is optimal because this concentration has the least unexplained variability. T. gondii exotoxin was stable for at least 18 months at -70 degrees C. The Toxoplasma HI test we report in this paper is shown to be a fast, easy, highly specific, and sensitive test for the diagnosis of toxoplasmosis.

Animals↗