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PubMed1989

Isolation of a potential DNA probe for Toxoplasma gondii.

A genomic DNA library for Toxoplasma gondii has been constructed in plasmid pUC8. Some recombinant plasmids (pJMBG1-pJMBG55) were analysed by restriction endonuclease mapping and by hybridization to DNA isolated from T. gondii and from human tissue culture cells. A number of recombinant plasmids, or DNA fragments derived from these, hybridizing only to Toxoplasma DNA have been identified. These are currently being characterized for the development of diagnostic DNA probes for Toxoplasma.

Animals↗
PubMed1989

[The effect of a subretinal injection of Toxoplasma gondii on the serum antibody titer in a rabbit model of ocular toxoplasmosis].

A single subretinal injection of RH toxoplasma initiated an experimental toxoplasmosis of the eyes in big chinchilla rabbits. This animal model was used to study the development of the serum IgG level against toxoplasma. As a rule, the specific antibody level rose between the 9th and the 20th day following injection. At that time, the peak of inflammation had already been exceeded. An influence of cyclophosphamide0 or complete Freund's adjuvant on the humoral immune response of the animals to toxoplasma could not be detected. An attempt is made to interpret the findings deviating from the toxoplasmosis of the human eye.

Animals↗
PubMed1989

[Observations on the growth dynamics of 4 strains of Toxoplasma gondii in HeLa cells].

Growth dynamics of PP, CN and ZS2 strains of Toxoplasma gondii isolated in China was studied and compared with that of RH strain. HeLa cells were used in this work. It took only 2 min for the organisms of RH strain to infect the HeLa cells when contacting with the cells. By contrast, the CN strain requires 5 min, the ZS2 and PP strains, 10 min. Toxoplasma began its multiplication after a lag time of about 6 h in the HeLa cells. The mean generation time of the 4 strains was assessed by calculating the number of the parasites in the parasitophorous vacuoles at different incubation times and by the linear regression equation. The results showed that the mean generation time was 5.2 h for RH strain, 5.98 h for CN strain, 6.78 h for ZS2 strain and 7.69 h for PP strain. Among the 3 strains of Toxoplasma gondii isolated in China. CN strain was similar to RH strain in their infectivity and proliferation.

Animals↗
PubMed1988

In vitro generation of adherent mononuclear suppressor cells to Toxoplasma antigen.

Adherent mononuclear cells have been found to suppress the lymphocyte proliferation, of T lymphocytes of patients with various chronic infections, to pathogen-specific antigens. To explore mechanisms involved in the generation of these suppressor cells, we established an in vitro method for the generation of suppressor-adherent mononuclear cells. Adherent mononuclear cells separated from mononuclear cells from subjects with serological evidence of chronic Toxoplasma infection could be induced, by preincubation with Toxoplasma antigen for 8 days, to suppress the proliferative response to autologous mononuclear cells to Toxoplasma antigen (TA) (mean suppression = 47%) and tetanus toxoid (TT) (mean suppression = 39%) compared to the proliferative response of autologous mononuclear cells co-cultured with no antigen. When adherent cells were removed after 1-day culture there was no significant suppression of the lympho-proliferative response to TA or TT. Induction of the adherent suppressor cell depended on the presence of CD4-positive T cells and not CD8-positive T cells. Adherent suppressor cells acted directly on the proliferative response of CD4 cells to antigen. The adherent cells contained 90 +/- 5% esterase-positive cells. In cell-mixing experiments, equal numbers of CD8-positive T cells pretreated in a similar manner did not have a suppressive effect. However, pretreated CD4-positive cells did have a suppressive effect at higher concentrations of cells than found in the adherent cells. Indomethacin did not alter the suppressive effect. These studies demonstrate the induction of adherent suppressor cells in vitro and implicate the macrophage and CD4-positive T cells as the suppressor cells.

Animals↗
PubMed1988

[The production of hybrid cells producing monoclonal antibodies against Toxoplasma gondii].

Hybridomas that secrete monoclonal antibody to Toxoplasma gondii have been developed. Two groups of 10 female BALB/c mice each were immunized either over a shorter (71 d) or longer (117 d) period at first with Toxoplasma lysate antigen and afterwards with intact tachyzoites of the RH strain. Higher titres of antibody were obtained with the long-period immunization. The fusion experiments have shown that both schemes of immunization approximately result in the same number (16 and 14% respectively) of hybridoma cell lines producing antigen-specific monoclonal antibodies. Hybridoma cultures secreting antitoxoplasma monoclonal antibodies were screened parallel by indirect immunofluorescence antibody test (IFAT) and enzyme immunoassay (EIA). 16 of the hybridoma cell cultures produced positive results only in the IFAT, 112 reacted only in the EIA and 21 were positive in both tests. The monoclonal antibodies 5B10, 5G6 and 1B2, which are positive in the IFAT form a chemical compound with the major antigens on the surface of RH tachyzoites. The patterns of fluorescence produced by these monoclonal antibodies are in conformity with those produced by using polyclonal sera of Toxoplasma gondii infected hosts (mouse, rabbit, man).

Animals↗
PubMed1986

Acute toxoplasma infection of mice induces spleen NK cells that are cytotoxic for T. gondii in vitro.

Murine spleen natural killer (NK) cells from normal and Toxoplasma-infected BALB/c mice were examined for their reactivity against RH strain tachyzoites in vitro. First, the effect of suspending medium on survival of extracellular RH tachyzoites was determined. Optimal parasite viability (by ethidium bromide-acridine orange staining) was observed when tachyzoites were incubated in phosphate-buffered saline (PBS) containing 10% horse serum (HS) for as long as 5 hr. In addition, parasite viability in PBS-HS correlated with subsequent infectivity, because freshly harvested and PBS-HS-incubated tachyzoites were equivalent in their ability to cause lethal infections in normal mice and to survive within normal mouse macrophages. Furthermore, viability and tumoricidal capacity of murine spleen NK cells incubated in PBS-HS was comparable to that of NK cells incubated in a standard cytotoxicity medium. Incubation of effector NK cells and target tachyzoites in PBS-HS in vitro revealed that spleen NK cells from 3-day Toxoplasma-infected mice had significantly greater cytotoxicity for extracellular RH tachyzoites than did control cells from uninfected mice. Moreover, Toxoplasma gondii-induced spleen NK cell toxoplasmacidal activity was significant at all effector to target cell ratios tested, and appeared to be mediated by direct contact between the host cell and the parasite. These in vitro results suggest that NK cells may be important in host defense against T. gondii.

Acute Disease↗
PubMed1986

Prevalence of Toxoplasma gondii among West African rodent, Thryonomys swinderianus from the Niger Delta.

The prevalence of Toxoplasma gondii among West African rodent, Thryonomys swinderianus, was assessed by the Sabin-Feldman dye-test. All of the 104 animals examined in the study were seropositive for Toxoplasma dye-test antibody. This indicates that there exists among these rodents a considerable reservoir of Toxoplasma from which infection can be transmitted to man and other animal species in that area.

Animals↗
PubMed1985

Toxoplasma gondii infection of cats in Beirut, Lebanon.

The prevalence of serum antibodies to Toxoplasma gondii was determined by the indirect fluorescent antibody (IFA) test in cats of Beirut, Lebanon from September 1980 to July 1983 (35 months). Testing revealed that 253/324 (78.1%) cats had antibodies in the IFA test. While the prevalence of Toxoplasma antibodies in stray cats was considerably greater than in owned cats at the beginning of the study, this difference diminished over time, and prevalence was similar by the end of the study. Faecal shedding of Toxoplasma-like oocysts was found in 31/313 (9.9%) of cats, while 38/313 (12.1%) shed other Isospora spp. oocysts. The occurrence of dual infections was statistically significant.

Animals↗
PubMed1979

Propagation of Toxoplasma gondii in suspension cultures of HeLa cells.

A novel method of Toxoplasma gondii cultivation in suspension cultures has been introduced using silicone-coated glass vessels (working volume 100 ml). The cells were kept in suspension by a magnetic impeller at 75 rpm at a temperature of 37 degrees C. HeLa cells grown on MEM with calf serum were used as host substrate. The HeLa cells were infected with zoites of Toxoplasma gondii virulent P strain. After seven days the host cells were destroyed by the toxoplasmas and the number of zoites was up to 24 x 10(6)/ml.

HeLa Cells↗
PubMed1985

Persistence of encysted Toxoplasma gondii in tissues of equids fed oocysts.

Thirteen 6-month- to 13-year-old equids were each inoculated orally with 10,000 infective Toxoplasma gondii oocysts. The equids remained clinically normal. Equids were euthanatized on postinoculation days 33, 45, 90, 104, 120, 140, 162, 183, 197, 204, 211, 294, and 476. Their tissues were bioassayed for viable oocysts by feeding muscles to Toxoplasma-free cats and by inoculation of pepsin digests of 13 organs into mice. Using mouse inoculation, T gondii was recovered from tissues of the 9 equids euthanatized on each of postinoculation days 33, 45, 120, 140, 183, 197, 211, 294, and 476. Toxoplasma gondii was isolated from the tongue and intestines of 4 equids, from the heart of 3 equids, from thigh muscles, brain, and heart of 2 equids, and from the eye, lungs, and spinal cord of 1 equid. Muscles from 9 of 13 equids were infectious to cats, as evidenced by feline shedding of oocysts. Results indicate that T gondii can persist in edible tissues of living equids up to 476 days and that non-cooked horsemeat should not be fed to cats or eaten by human beings.

Abattoirs↗
PubMed1979

Density gradient centrifugation for separation of different stages of Toxoplasma gondii.

Suitable procedures for separation of various stages of Toxoplasma gondii by density gradient centrifugation have been delineated using peritoneal exudate of infected mouse as a model. Separation from host cells was effected by gradient centrifugation at 450 g for 30 minutes. Using Ficoll, dextran and sucrose, average parasite recoveries by pooling up to and including the peak fraction of 73.65%, 66.18% and 65.68% respectively were obtained. Toxoplasma trophozoites peaked at density of 1.040 g/ml with Ficoll, 1.060 g/ml with dextran and 1.110 g/ml with sucrose. In view of successful separation of exo-enteric stages of Toxoplasma by density gradient centrifugation, possible application of this method to isolation of various endo-enteric stages is discussed.

Animals↗
PubMed1979

Biology of Toxoplasma gondii, its survival in body tissues and liquids, risks for the pregnant woman.

After briefly outlining the biology of Toxoplasma gondii the authors discuss the resistance of the parasite in body liquids and tissues under certain environmental conditions. Parasite resistance and its consequent risk of human infection, particularly for the pregnant woman, is emphasized. Toxoplasma oocysts, the sexual expression of the parasite, and the cyst facilitate the diffusion of Toxoplasma, as they are much more resistant than the trophozoite.

Animals↗
PubMedDate not supplied

[Toxoplasmas of wild warm-blooded animals in Turkmenia].

Antibodies to Toxoplasma in the reaction of indirect hemagglutination were found in 8 species of mammals and 2 species of birds. Carriage of antibodies to Toxoplasma in house mouse, common fox, bald coot , and rock-dove was first recorded from Turkmenia . Analysis of the infection with Toxoplasma according to species, habitat of antibodies carriers, their ecology, age, sex and season of investigation is given.

Animal Population Groups↗
PubMed1983

[Systemic lupus erythematosus, polymyositis and toxoplasma antibodies].

High toxoplasma antibody titers have been reported in polymyositis and other connectivitis with myositis. The authors describe a case of systemic lupus erythematosus with polymyositis and high titers of IgG toxoplasma antibodies. Studies of muscle biopsy specimens by immunofluorescence and inoculation of mice with muscle extracts failed to demonstrate the presence of Toxoplasma gondii. The nature of the toxoplasmic agression is discussed. It may be that reactivation of a previous infection due to the rupture of cysts was promoted by the immunologic disorders and complement deficiency related to systemic lupus erythematosus.

Adult↗
PubMed1982

Prevalence of Toxoplasma antibodies in pregnant African women in Tanzania.

Three hundred and fifty-seven serum samples from pregnant African women were examined for Toxoplasma gondii antibodies with indirect haemagglutination test in Dar es Salaam. Out of these 222 women were normal, sixty-nine had anaemia and sixty-six were suffering from hypertension. Infection rate in normal pregnant women was 41.9%, in anaemic women 52.5%, and in those suffering from hypertension 66.7%. Highly significant relationship was observed between Toxoplasma infection and anaemia, and hypertension. Infection rate was significantly high in women who had histories of abortion. The results suggested associations of Toxoplasma gondii infection with hypertension and anaemia in African women.

Adult↗
PubMed1983

A solid-phase indirect haemadsorption assay (SPIHA) for detection of immunoglobulin m antibodies to Toxoplasma gondii: application to diagnosis of acute acquired toxoplasmosis.

A solid-phase indirect haemadsorption assay (SPIHA) for the detection of immunoglobulin M (IgM) antibodies to Toxoplasma gondii is described. Polystyrol microtiter plates are coated with anti-human IgM (mu-chain-specific) antibodies and then sequentially allowed to react with patient's serum and sheep erythrocytes sensitized with soluble antigen of Toxoplasma gondii. A total of 111 sera were tested in fluorescent antibody test (FAT and IgM-FAT), complement fixation test (CFT), indirect haemagglutination assay (IHA), and in SPIHA. 47 sera were from individuals with a suspected or verified acute Toxoplasma infection. In most of these cases the SPIHA allowed a clear interpretation with respect to the status of the infection, even when the IgM-FAT was not conclusive. In contrast to IgM-FAT, rheumatoid factor or exceedingly high specific IgG antibodies did not interfere with results in SPIHA. A laboratory-acquired infection enabled us to demonstrate the course of immune response measured by SPIHA as well as by IgM-FAT, FAT, CFT, and IHA. The method proposed here is well appropriated to IgM detection, simple to perform, inexpensive, and thus representing an alternative to IgM-FAT, convenient for the routine laboratory.

Complement Fixation Tests↗
PubMed1984

Prevalence of Toxoplasma antibodies in Chiang Mai population.

Five hundred sera from blood donors were examined for antibodies to Toxoplasma by the indirect hemagglutination antibody (IHA) and the indirect fluorescent antibody (IFA) techniques. In addition, the IHA test was used to detect Toxoplasma antibodies in 500 pregnant women's sera. It was found that 4.6% of the blood donors were positive by the IHA and only 1.2% by the IFA methods. The seroprevalence, however, was less in pregnant women as only 2.8% were positive. Interestingly, 7.5% of the blood donors and 15.2% of pregnant women showed no detectable antibodies. The frequency distribution curves of IHA titers were unimodal in both groups studied. From the basis of these findings, it was concluded that there was a low degree of Toxoplasma transmission in Chiang Mai.

Adult↗
PubMed1983

Preparation of a Toxoplasma gondii agar gel immunodiffusion test antigen from ovine fetal kidney cell cultures.

A toxoplasma gondii antigen prepared from the cell-free supernatant of ovine fetal kidney (OFK) cell cultures produced a sharp precipitation line against anti-Toxoplasma serum in an agar-gel immunodiffusion (AGID) test. Results obtained from the AGID and indirect hemagglutination (IHA) tests on 46 human and nine rabbit sera were compared. Thirty-three percent of the serum samples, which were negative for the Toxoplasma IHA test, were positive when assayed by the AGID method. The AGID test appears to be superior to the IHA test for detecting low titers of antibodies against T. gondii. After 70 generations of serial passages through the OFK cell cultures, T. gondii still produced the AGID test antigen.

Animals↗