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PubMed1988

Modification of host cell phagosomes by Toxoplasma gondii involves redistribution of surface proteins and secretion of a 32 kDa protein.

Toxoplasma gondii resists endocytic processing within host cell phagosomes that are modified by a prominent membranous network which forms the interface between host cell and the enclosed parasite. The formation of this intravacuolar network involves redistribution of the major outer membrane proteins of the Toxoplasma cell, consisting of 41, 35, 29, 22 kDa species, as shown by radioimmunoprecipitation, sodium dodecyl sulfate polyacrylamide gel electrophoresis, and immunogold EM labeling using monoclonal antibodies (mAbs) to T. gondii. In addition, the major 32 kDa protein found in the purified intravacuolar networks was recognized by mAb 1G5 which does not react with the surface of intact Toxoplasma cells. Immunoperoxidase EM using mAb 1G5 indicated that the 32 kDa protein is a constituent of electron-dense vacuoles within the Toxoplasma cell, in addition to being a prominent component of the intravacuolar network. Thus, assembly of the intravacuolar network appears to involve regulated release of the 32 kDa protein in conjunction with shedding of surface membrane proteins by the parasite. Our results suggest that the structural modifications of host cell phagosomes by T. gondii are precisely regulated events that follow invasion and consequently may contribute to intracellular survival.

Animals↗

PubMed1988

[In vitro measurement of the inhibitory effect of macrolides, lincosamides and synergestines on the growth of Toxoplasma gondii].

The in vitro inhibitory effect of macrolides, synergestines and lincosamides on Toxoplasma gondii was evaluated using an enzyme immunoassay performed directly on the infected cultures. Antimicrobial agents were tested at various concentrations, and regression models were used to quantify the relationship between optical density values (correlated to Toxoplasma count in the cultures) and drug concentrations in the cultures. A significant inhibitory effect was observed with the macrolides (erythromycin, roxithromycin, midecamycin, spiramycin, josamycin and oleandomycin) for concentration of 0.1 to 4 micrograms/ml. This effect progressively increased with increasing concentration of drug in the cultures and reached its maximum value for concentrations of 40 to 250 micrograms/ml. Similarly, clindamycin was found to have a significant inhibitory effect for concentration ranging from 0.5 ng/ml to 100 micrograms/ml. Only a partial inhibitory effect was noted with virginiamycin, pristinamycin and lincomycin. The concentrations giving a 50% inhibition of Toxoplasma growth in the culture were determined from regression models and ranged between 0.15 and 12 micrograms/ml according to the drug. This results confirm that macrolides, lincosamides are effective against Toxoplasma gondii in vitro, and can be proposed for treatment of toxoplasmosis because of their large diffusion, their good tolerance and their concentration in tissues such as lung and placenta.

Animals↗

PubMed1986

[Incidence of Toxoplasma gondii oocysts in cat feces].

Within two years and a half, the faeces of 620 cats coming from Brno and the area around the city were subjected to parasitological examination with special regard to the occurrence of the oocysts of Toxoplasma gondii. Sucrose solution at the specific weight of 1,150 was used as flotation medium. Oocysts of Toxoplasma gondii were eliminated by eight cats (1.29%) at the age from 16 days to 1.5 years. Six of the eight cats were younger than seven months. The Toxoplasma gondii oocysts were eliminated by the cats for 1-16 days while exhibiting signs of short-term scours and swelling of lymph nodes. In all cases the oocysts of Toxoplasma gondii were produced in the summer and autumn seasons (June-December). During the patent period, other coccidia (Isospora felis and Isospora rivolta) were also present in the cats.

Animals↗

PubMed1977

Search for the presence of lectin-binding sites on Toxoplasma gondii.

Evidence for the presence of carbohydrate on the surface membrane of Toxoplasma gondii trophozoites and on the cell wall of toxoplasma brain cysts was sought by fluorescent lectin staining. Using FITC-conjugated preparations of Concanavalin A (Con A), wheat germ agglutinin (WGA), or soy bean agglutinin (SBA), we have failed to obtain evidence for the binding of these lectins on the surface of T. gondii trophozoites. In contrast, the three test lectins bound effectively and specifically to the wall of toxoplasma brain cysts. Prefixation of cysts with glutaraldehyde or brief trypsinization of cysts did not affect the intensity of cyst wall fluorescence when stained with FITC-conjugated Con A, SBA, or WGA. The results are interpreted to indicate that whereas exposed Con A, SBA, and WGA binding sites are associated with the wall of toxoplasma brain cysts, such lectin-binding saccharide residues are not present on the surface of trophozoites in exposed or reactive form.

Animals↗

PubMed1983

Augmentation of NK cell activity by soluble and particulate fractions of Toxoplasma gondii.

The ability of sonicates of Toxoplasma gondii and of subcellular fractions of the organism to enhance natural killer (NK) cell activity in mice was examined. Treatment of BALB/c mice with the sonicate preparations enhanced peritoneal and splenic NK activity to the level obtained with intact tachyzoites. Similar augmentation of NK activity in A/J, C57BL/6, and C3H/HeJ mice was also observed. Administration of Toxoplasma sonicate intraperitoneally, intravenously, or subcutaneously enhanced both peritoneal and splenic NK activity. Treatment of mice with a sonicate of L929 fibroblast failed to enhance their NK activity. Concentrations of sonicates ranging from 400 to 4 micrograms of protein enhanced both peritoneal and splenic NK activity. Both the soluble and particulate fractions of the sonicate obtained by differential centrifugation were capable of enhancing peritoneal NK activity, whereas splenic NK activity was enhanced only by the particulate fraction. Heat, protease, and sodium periodate treatment of the Toxoplasma sonicate completely abolished its capacity to augment NK activity. Gel filtration studies revealed that the NK augmenting activity of the Toxoplasma sonicate is distributed over a wide molecular weight range.

Animals↗

PubMed1980

Prevalence of antibodies including IgM to Toxoplasma gondii in Malaysians.

A total of 736 sera collected from cord blood babies, children and adults of both sexes and of different age groups in Malaysia were tested using indirect fluorescent antibody technique for Toxoplasma antibodies. The RH strain of Toxoplasma gondii zoites were used as antigen. One hundred and twenty five sera which were reactive at 1:64 or high titres were tested with IgM specific conjugate. Results of the present studies showed that the prevalence of Toxoplasma antibody was highest among the Malays and lowest among children than among adults. The significance of Toxoplasma specific IgM was discussed.

Adolescent↗

PubMed1982

Isolation of Toxoplasma from the soil during an outbreak of toxoplasmosis in a rural area in Brazil.

During an outbreak of human toxoplasmosis attempts were made to isolate Toxoplasma from soil near Além Paraíba, Brazil. Five soil samples were collected from the gardens and also from humid shady areas near the houses. After several washings, these soil samples were centrifuged in a glucose solution, and the supernate removed to be centrifuged in water. The sediments obtained from each of the five soil samples were then inoculated orally in groups of mice. Only one soil sample, obtained from a vegetable garden, gave rise to infection in mice. Toxoplasma-like cysts were found in the brains of two mice and also a few mice from all the four subsequent passages. Cyst-positive mice presented antibodies against T. gondii. Two young cats, seronegative by the Sabin-Feldman dye test, subsequently ingested the cyst-positive mouse brain. One cat eliminated Toxoplasma-like oocysts between the 5th and 11th days after the infection and the other cat between the 6th and 16th days. Seroconversion was observed in both cats, 15 days after the inoculation. These results further emphasize sanitary precautions essential to the control of Toxoplasma.

Animals↗

PubMed1980

Detection and characterization of membrane antigens of Toxoplasma gondii.

Toxoplasma gondii tachyzoites were surface radioiodinated by the lactoperoxidase technique, and the solubilized membrane proteins were analyzed by two-dimensional polyacrylamide gel electrophoresis. Four major labeled proteins with apparent m.w. of 43,000, 35,000, 27,000, and 14,000 were detected. None of the radioiodinated proteins bound to concanavalin A-Sepharose. When a panel of eight different fluorescein-conjugated lectins was used in an attempt to characterize further the nature of the cell membrane, none of the lectins bound to intact tachyzoites. Two-dimensional polyacrylamide gel electrophoresis did not reveal any significant differences among three different strains of Toxoplasma. Each of the radioiodinated surface proteins was precipitable by sera from mice chronically infected with the same strain as well as by a series of sera from mice infected with other strains. Sera from humans with acute Toxoplasma infection showed more variability in that some precipitated all labeled proteins whereas others precipitated only two or three of them. Monoclonal antibodies (2G11 and 3E6) prepared by hybridization of spleen cells from Toxoplasma-immune mice with myeloma cells consistently precipitated both the solubilized 35,000 and 14,000 dalton proteins, whereas 1E3 precipitated the 43,000-dalton protein and 1E11 the 27,000-dalton protein.

Animals↗

PubMed1995

[Toxoplasma gondii: perspectives for a vaccine].

To date no single vaccine has been commercialized in the field of human parasitology, and therefore a practical approach to a potential Toxoplasma vaccine in the field can only be discussed theoretically. The aim of such a vaccine would consist either in inhibiting endogenous parasite multiplication (tachyzoite formation) and thus dissemination, or in preventing the final formation of Toxoplasma cysts (bradyzoite formation). Immune protectivity should confer resistance to disease and parasite dissemination in pregnant women, in order to prevent congenital toxoplasmosis in the unborn infant, and prevent cyst formation in order to avoid reactivation in case of future immunosuppression of the individual. The establishment of a successful protective immunity was elucidated in the mouse model: the number of formed Toxoplasma cysts is primarily regulated by the function of Toxoplasma-specific CD8(+)-T-cells. Direct effector functions of cytotoxic CD8+ lymphocytes directly depend on local periparasitic gamma-interferon- and TNF alpha-concentrations. Immunological aberrance occurs if locally (cerebral) synthesized Il-10 and Il-6 induce anergistic immunosuppression. An experimental vaccine in the mouse demonstrated primary dependence of a protective immune response on CD8+ and CD4+ (Th) cells. Experimental vaccines within domestic animals concentrate mainly on the development of temperature-sensitive mutants of the T. gondii RH-strain, which will protect animals from disease but not from infection and cyst formation.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1995

Different subsets of T cells in conjunction with natural killer cells, macrophages, and activated microglia participate in the intracerebral immune response to Toxoplasma gondii in athymic nude and immunocompetent rats.

Oral infection of athymic nude and immunocompetent Lewis rats with Toxoplasma gondii induced a chronic nonlethal encephalitis. The histopathological pattern of Toxoplasma encephalitis was significantly different in both groups of animals and there were substantially larger numbers of Toxoplasma cysts in the brains of athymic rats. Combined immunohistochemical and flow cytometric analyses of intracerebral leukocytes identified alpha beta TCR+ CD4+ and CD8+ T cells; macrophages, and natural killer cells as inflammatory cell populations in immunocompetent rats, whereas in athymic rats natural killer cells, macrophages, and gamma delta TCR+ CD8+ CD3+ T cells contributed to the intracerebral inflammatory infiltrates. These findings not only point to a major participation of alpha beta TCR+ T cells to the intracerebral immune response, but also indicate that they are not essential to prevent the development of a lethal Toxoplasma encephalitis. In addition, microglia were strongly activated in both strains with simultaneous up-regulation of major histocompatibility complex class I and II antigens and CD4. Activation of microglia was most prominent in athymic rats, demonstrating that immunodeficiency does not preclude an up-regulation of these molecules including the human immunodeficiency virus receptor CD4 on microglial cells.

Animals↗

PubMed1994

gamma delta T cells play a crucial role in the expression of 65,000 MW heat-shock protein in mice immunized with Toxoplasma antigen.

Toxoplasma gondii is an obligate intracellular protozoan parasite and cellular immunity plays a crucial role in protection against infection with this pathogen. When mice are immunized with Toxoplasma homogenate, they readily acquire resistance against infection with a lethal dose of a low virulence Beverley strain of T. gondii. We have reported previously that expression of 65,000 MW heat-shock protein (hsp 65) in host macrophages closely correlates with protective potentials of hosts, while this protein is not expressed in Toxoplasma themselves. In this study, we examined the mechanism of expression of hsp 65 in mice immunized with Toxoplasma homogenate. Heat-shock protein was detected in peritoneal macrophages of BALB/c mice immunized 7 days previously by electroblot assay with a specific monoclonal antibody (mAb) for microbial hsp 65. Furthermore, an immunogold ultracytochemistry assay demonstrated that this protein was expressed on the cell surface of peritoneal macrophages in immune mice. This expression was not induced in those of immune athymic nude mice and SCID mice. Treatment of BALB/c mice with anti-Thy-1.2 mAb 1 day before immunization led to an almost complete loss of the expression of hsp 65. To determine the subsets of T cells responsible for induction of this protein, mice were depleted of gamma delta T cells, alpha beta T cells, CD4+ T cells or CD8+ T cells by treating with corresponding antibodies before immunization. From these experiments, gamma delta T cells were shown to be essential for the expression of hsp 65, although CD4+ alpha beta T cells also contributed to some extent. Thus, gamma delta T cells appear to play an important role in protective immunity against infection with T. gondii through mediating the expression of hsp 65 in host macrophages.

Animals↗

PubMed1993

[Detection of circulating antigen in urine from mice infected with Toxoplasma tachyzoites].

Urine samples collected from three groups of mice infected experimentally with different numbers doses of Toxoplasma trophozoites were detected for the presence of Toxoplasma circulating antigen by using fast ELISA. The results showed that presence of circulating antigen in all three infected groups of mice in comparison with the normal control group. Toxoplasma circulating antigen was detected on days 5, 4 and 3 after infection in light-, moderate- and heavy-infection groups, respectively. The concentration of circulating antigen was on a parallel with the duration of infection. Western blot analysis of the Toxoplasma circulating antigen in urine revealed the existence of seven specific bands with molecular weights of 75, 67, 55, 43, 30, 28 and 22 kDa.

Animals↗

PubMed1995

Incidence of Toxoplasma and Toxocara antibodies among out-patients in the Ophthalmic Research Institute, Egypt.

Infection by Toxoplasma gondii and Toxocara canis is getting much important nowadays. Both are soil transmitted infections. The present study was planned to detect the incidence of T. gondii and T. canis antibodies among 100 patients attending the outpatient clinics in Research Institutes of Ophthalmology (RIO), whose urine and stool were free from other parasitic stages. Patients were classified into two groups, group I; (70 ocular cases) and group II, (30 non-occular cases). Control group (group III); 30 healthy persons. Sera from all individuals were subjected to IFAT and IHAT to detect Toxoplasma antibodies and IFAT to detect Toxocara antibodies. By using IFAT for Toxoplasma revealed, 25% as a total incidence, 21.4% in group I, 33.3% in group II and 6.6% in group III. While IHAT revealed 51% as a total incidence, 51.4% in group I, 50% in group II and 23.3% in group III. Among group I, retinochoroiditis cases showed the highest incidence and titre. While hydrocephalic cases showed highest incidence and titre in group II. T. canis antibodies revealed 23% as a total incidence, 14.3% in group I, 43.3% in group II and 5% in group III. Cases presented with retinal detachment showed the highest incidence and titre in group I while in group II hepatomegalic cases gave the highest incidence and titre. Concomitant infection of both Toxoplasma and Toxocara was detected in 8% of positive cases.

Animals↗

PubMed1995

Toxoplasma IgG. & IgM. antibodies. A case control study.

This study includes 62 cases of spontaneous abortions and 75 cross matched non pregnant multiparous women as controls. Micro-ELISA test was done to measure Toxoplasma IgM & IgG antibodies. Out of 62 aborting women, 26 gave positive anti-Toxoplasma IgG antibodies, more than 45 Eu/ml and 28 gave positive anti-Toxoplasma IgM antibodies, more than 40 Eu/ml without statistical significant difference. There was a significant difference between aborting women and the controls as regards IgG & IgM antibodies. IgG antibodies, showed statistical significant difference between those with no history of abortions or I-2 abortions versus those with 3 or more abortions. The infection was more among aborting women in rural than urban areas whom suffered poor hygienic measures and awareness about the mode of transmission of Toxoplasma infection. The results were discussed.

Abortion, Spontaneous↗

PubMed1996

Natural toxoplasma infection sought in the Indian grey mongoose (H. edwardsi, Greffroy, 1818) trapped in the eastern region., Saudi Arabia.

No doubt, the world wide distributed Toxoplasma gondii is more prevalent in nearly all the Middle East countries including Saudi Arabia. In this paper, natural Toxoplasma infection was sought in six mongooses trapped in the Eastern Region of the Kingdom. Four had seropositivity by the indirect haemagglutination tests (IHAT), the parasite was demonstrated in the spleen smears of two of them and Toxoplasma parasites were successfully isolated by mice I.P. inoculation from one of them. The results were discussed. It was concluded that Toxoplasma infection, a zoonotic protozoal parasite, is increasing in Saudi Arabia and its epidemiological status should be studied.

Animals↗

PubMed1996

Prevalence of Toxoplasma gondii and cytomegalovirus antibodies in patients with chronic renal failure.

This study aimed to determine the prevalence of Toxoplasma gondii and cytomegalovirus (CMV) antibodies in patients with chronic renal failure (CRF) with and without haemodialysis. To achieve this goal, 60 patients with CRF in addition to 20 healthy controls were investigated. Patients were classified into 3 groups, group 1 comprised 20 patients with CRF who haven't any haemodialysis sessions (under conservative treatment) group II comprised 20 patients with CRF due to primary renal diseases already on haemodialysis and group III comprised 20 patients with renal failure secondary to collagen disease or accompanied by liver disease undergoing haemodialysis. Out of 60 patients, Toxoplasma antibodies were detected in 38.3% and in 15% of the normal controls with a statistical significant difference. From the present results, it was noticed high percentages of positivity for Toxoplasma and CMV antibodies in patients with CRF undergoing haemodialysis which was also correlated to the number of the dialysis sessions. So, it can be concluded that CRF patients undergoing haemodialysis should be screened for Toxoplasma and cytomegalovirus before dialysis to prevent the dissemination of these infections through dialysis procedure.

Adult↗

PubMed1996

Antibodies against toxoplasma in children and adults with malignancy.

Twenty five children and adults with different types of malignancies were picked up from the attendants of Mansoura University Hospital and Ain Shams University Paediatrics Hospital. Their sera were examined for anti-Toxoplasma IgG and IgM antibodies by the micro-ELISA before and after chemotherapy treatment. Ten normal cross-matched individuals were selected as a control group. The results revealed seropositive IgG in 22 (88%) of patients before treatment and in 23 (92%) after treatment. The anti-Toxoplasma IgM was positive in three (12%) patients before treatment and in six (24%) after treatment. On the other hand, two of the control group showed a seropositive Toxoplasma IgG (20%) but negative anti-Toxoplasma IgM. The results were discussed.

Adolescent↗

PubMed1997

Anti-toxoplasma antibodies in butchers and slaughtered sheep and goats in Jeddah Municipal abattoir, Saudi Arabia.

Toxoplasma gondii is a zoonotic parasite of world-wide distribution. It is more or less endemic in all countries of the Middle East. In Jeddah Municipal abattoir, anti-Toxoplasma IgG was found to be 39% in sheep and 28% in goats as indicated by IHAT. On the other hand, anti-Toxoplasma IgG and IgM in butchers were 80% and 20% respectively, as indicated by the micro-ELISA. The risk of Toxoplasma transmission particularly, from meat inadequately cooked was discussed.

Abattoirs↗