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PubMed1987

In vivo and in vitro activity of roxithromycin against Toxoplasma gondii in mice.

Roxithromycin protected mice against a lethal infection with the extremely virulent RH strain and the C56 strain of Toxoplasma gondii. Therapy initiated 2 h after infection with 2 X 10(3) or 2 X 10(4) RH or C56 tachyzoites protected more than 80% of the mice, compared with 0% of untreated controls (p less than 0.001). Paradoxically, Toxoplasma gondii was isolated more frequently (greater than 80%) in treated mice surviving infection with the less virulent strain (C56) than those surviving infection with the more virulent RH strain (less than 25%). Furthermore, in vitro studies revealed that roxithromycin at dosages up to 250 micrograms/ml had no effect on the proliferation of Toxoplasma gondii in murine peritoneal macrophage cultures.

Acute Disease↗

PubMed1986

Serodiagnosis of human G and M immunoglobulins to Toxoplasma gondii by ELISA using whole tachyzoites as antigens: a comparative study with the indirect haemagglutination (IHA) and immunofluorescence (IFA) tests.

An indirect ELISA using whole tachyzoites of Toxoplasma gondii fixed onto the bottom of microtiter plate wells is described for detection of specific G and M anti-toxoplasma antibodies. ELISA results were compared with those of IFA and IHA tests. Similarity of antigens (cell surface) involved in ELISA and IFA permits high correlation between the two tests (r = 0.84-0.93, P less than 0.001) and results in good accordance for negative sera. As ELISA offers several advantages over the classical IFA test, it may be considered an alternative method for screening of G and M anti-toxoplasma antibodies.

Animals↗

PubMed2000

Clinical and diagnostic relevance of the Toxoplasma IgG avidity test in the serological surveillance of pregnant women in Austria.

For evaluation of the medical relevance of a Toxoplasma IgG avidity test within the Austrian program for screening of pregnant women, 23 sera from women with seroconversions (group 1) and with proven latent Toxoplasma infections (group 3), respectively, as well as 92 sera from women suspected of having a primary infection (group 2) were tested by the indirect immunofluorescence test (IFAT), Sabin-Feldman's dye test (SFT), IgM enzyme-linked immunofluorescence assay (ELFA-IgM), IgA microparticle enzyme immunoassay, and the IgG avidity test. Group 1 sera (seroconversions) revealed a median avidity index (AI) of 0.25, whereas the median AI of group 3 sera (latent infections) was 0.66. In 31 (33.7%) of 92 cases suspected of involving a primary Toxoplasma infection, low (<0.41) or borderline AIs (0.41-0.50) were assessed, and in 61 cases (66.3%) the AIs exceeded 0.50. Finally, a recent infection could be excluded due to the results of the IgG avidity test in 59 cases; in at least 34 IgM-positive cases an unnecessary and, thus, unjustified treatment could be avoided.

Animals↗

PubMed2006

Women infected with parasite Toxoplasma have more sons.

The boy-to-girl ratio at birth (secondary sex ratio) is around 0.51 in most populations. The sex ratio varies between societies and may be influenced by many factors, such as stress and immunosuppression, age, primiparity, the sex of the preceding siblings and the socioeconomic status of the parents. As parasite infection affects many immunological and physiological parameters of the host, we analyzed the effect of latent toxoplasmosis on sex ratios in humans. Clinical records of 1,803 infants born from 1996 to 2004 contained information regarding the mother's age, concentration of anti-Toxoplasma antibodies, previous deliveries and abortions and the sex of the newborn. The results of our retrospective cohort study suggest that the presence of one of the most common parasites (with a worldwide prevalence from 20 to 80%), Toxoplasma gondii, can influence the secondary sex ratio in humans. Depending on the antibody concentration, the probability of the birth of a boy can increase up to a value of 0.72, C.I.95 = (0.636, 0.805), which means that for every 260 boys born, 100 girls are born to women with the highest concentration of anti-Toxoplasma antibodies. The toxoplasmosis associated with immunosuppression or immunomodulation might be responsible for the enhanced survival of male embryos. In light of the high prevalence of latent toxoplasmosis in most countries, the impact of toxoplasmosis on the human population might be considerable.

Animals↗

PubMed2002

In vitro effects of gliotoxin, a natural proteasome inhibitor, on the infectivity and proteolytic activity of Toxoplasma gondii.

We examined the in vitro effect of increasing gliotoxin concentrations on the infectivity of Toxoplasma gondii for NIH-3T3 murine fibroblasts and on Toxoplasma chymotrypsin-like activity, which is specific to the proteasome. Parasite penetration of host cells was not modified by a high gliotoxin concentration (1 microM), but replication was markedly decreased (approximately 50% inhibition by 0.5 microM gliotoxin). Gliotoxin reduced the chymotrypsin-like activity of the Toxoplasma proteasome, but five times less potently than in HeLa cells.

Animals↗

PubMed2001

Transcriptional profile of Toxoplasma gondii-infected human fibroblasts as revealed by gene-array hybridization.

To investigate the host-cell response to infection with the obligate intracellular pathogen Toxoplasma gondii, the transcriptional profiles of infected and uninfected human fibroblasts (HFF) were determined by hybridization to gene arrays representing nearly 600 genes. Transcripts that displayed a greater than five-fold increase in level relative to uninfected controls were also examined by RT-PCR and Northern analysis, resulting in the identification of 13 genes that were strongly up-regulated after infection with T. gondii. Comparisons with the transcriptional profiles of fibroblasts infected with Salmonella typhimurium and Chlamydia trachomatis allowed the identification of genes which are specifically induced in T. gondii-infected cells. While most of the up-regulated genes were induced on infection with all three pathogens, the genes for the transferrin receptor and MacMARCKS were up-regulated in Toxoplasma-infected fibroblasts only. Expression of the transferrin receptor protein was examined by Western analysis and found to be specifically elevated in Toxoplasma-infected fibroblasts. Genes which are specifically induced in T. gondii-infected cells are particularly interesting for further studies, since they might be used to dissect specific interactions of this pathogenic parasite with its host cell.

Animals↗

PubMed2003

Unspecific reactivity of IgM directed against the low-molecular-weight antigen of Toxoplasma gondii.

During routine serological survey, eight patients (5 pregnant women, 3 grafted patients) were positive for Toxoplasma gondii-specific IgM by enzyme-linked immunoassay but negative by a simultaneously performed immunosorbent agglutination assay. No clinical or biological symptoms of toxoplasmosis were observed later, despite the absence of treatment. Only one IgM-reactive band, which corresponded to the low-molecular-weight antigen of Toxoplasma gondii, was observed by Western blotting of these patients' sera. Dot blotting of lipid extracts of Toxoplasma gondii demonstrated that this reactivity was directed against sphingolipids or ceramides. This IgM positivity, which is unrelated to acute toxoplasmosis, raises strong concerns about the possibility of misleading results of this test in the diagnosis of toxoplasmosis in humans.

Animals↗

PubMedDate not supplied

Systemic T cell response to Toxoplasma gondii antigen in patients with ocular toxoplasmosis.

PURPOSE: Analysis of systemic cellular response to Toxoplasma antigen in patients with ocular toxoplasmosis. METHODS: Activated (CD25(+)) T cells were detected by flow cytometry after a 7-day culture of whole blood from patients with ocular (n = 16) or asymptomatic (n = 14) toxoplasmosis, and controls (n = 10), in the presence of soluble Toxoplasma antigen (ST-Ag). Interferon (IFN)-gamma, interleukin (IL) 4, and IL-10 were measured in culture supernatants by enzyme-linked immunosorbent assay. RESULTS: Higher percentages of CD25(+) T cells were detected in ST-Ag-activated cultures from Toxoplasma-infected patients, with or without ocular lesions (37.0 +/- 19.1% or 41.1 +/- 19.3%, respectively) than from controls (3.2 +/- 1.2%) (P < 0.0001). Differences were not statistically significant between asymptomatic and ocular toxoplasmosis (P > 0.4) or among congenital, acquired, and undetermined ocular toxoplasmosis (P > 0.2). Higher levels of IFN-gamma were detected in ST-Ag-stimulated blood cultures from infected patients than in those from controls (P < 0.0001), with no difference between patients with asymptomatic or ocular toxoplasmosis (P > 0.05). IL-10 was detected only in activated culture supernatants from three patients with ocular toxoplasmosis and two patients with asymptomatic toxoplasmosis. IL-4 was never produced in ST-Ag-activated cultures. CONCLUSIONS: Systemic cellular response to ST-Ag does not differ between the patients with ocular and asymptomatic toxoplasmosis with regard to activation markers and type 1 cytokine production.

Adolescent↗

PubMed1977

Uterine toxoplasma infections and repeated abortions.

Serologic testing for Toxoplasma antibodies (dye test, indirect fluorescent antibody test on serum, and complement-fixation test) was done in 96 women with habitual abortions and 61 women with sporadic abortions. In 61 of these women, endometrial biopsies were examined for content of T. gondii (animal inoculation procedures, immunofluorescence microscopy). Control subjects were 59 women with no spontaneous abortions. In seven patients (one control patient and six with habitual abortion), tachyzoites of T. gondii were observed in repeated biopsies from the endometrium and in menstrual blood by the immunofluorescence method. In no case, however, could T. gondii be isolated from the endometrium by inoculations. Moreover, the serologic results obtained among the patients with habitual abortion did not differ significantly from those obtained among the ones with sporadic abortion or among the control subjects. Five of the women with Toxoplasma-positive endometrium were serologically negative. Treatment of the Toxoplasma-positive women with antitoxoplasma drugs led to removal of parasites from the endometrium. T. gondii was not observed in the semen of the husbands.

Abortion, Habitual↗

PubMed1984

Macrophage-mediated suppression of immune responses in Toxoplasma-infected mice. I. Inhibition of proliferation of lymphocytes in primary antibody responses.

The suppressor cells induced by Toxoplasma infection were shown to be macrophages, since they adhered to plastic, and their suppressive activity in anti-sheep erythrocytes (SRBC) antibody responses was abrogated by treatment with silica or carrageenan, which are selectively cytotoxic for macrophages. The suppressor macrophages strongly inhibited the uptake of tritiated thymidine ( [3H]TdR) by normal mouse spleen cells in the responses to SRBC and Toxoplasma antigens. Supernatant fluids from the suppressor macrophages could not passively transfer the suppressive effect on anti-SRBC antibody responses. Furthermore, when the suppressor macrophages were isolated by a cell-impermeable membrane from normal mouse spleen cells, the antibody responses of normal spleen cells were not suppressed. These results indicate that suppression of antibody responses in Toxoplasma-infected mice is caused by an inhibitory effect of the suppressor macrophages upon proliferation of lymphocytes via direct contact with responder target cells. The suppressive effect of the macrophages was not counteracted by indomethacin, a potent inhibitor of prostaglandin synthesis, or catalase, a catabolic enzyme for hydrogen peroxide (H2O2).

Animals↗

PubMed1984

Enhancement of human natural killer cell activity by subcellular components of Toxoplasma gondii.

The ability of sonicates and subcellular fractions of the intracellular parasite Toxoplasma gondii to enhance in vitro human natural killer (NK) cell activity was examined. Incubation of nylon-wool-non-adherent human peripheral blood lymphocytes (PBL) with sonicates of T. gondii for 18-72 hr resulted in increased NK activity against an NK-sensitive, as well as an insensitive, target cell. Single-cell assays revealed that augmentation of NK activity was not due to an increased binding of K562 target cells to effector cells. Differential centrifugation studies indicated that NK-augmenting activity was distributed in membrane-enriched and cytoplasmic fractions. This activity was found to be resistant to treatment with ribonuclease (RNase) and deoxyribonuclease (DNase), but susceptible to proteolysis. Antibodies present in the serum of humans infected with Toxoplasma blocked the NK cell-augmenting effect of the membrane-enriched fractions. Enhancement of NK activity by PBL incubated with Toxoplasma sonicate was accompanied by a concomitant increase in interferon (IFN), but not of interleukin 2 (IL-2), levels in supernatants of the cell cultures.

Adult↗

PubMed1994

Western blot analysis of the IgG response of sheep vaccinated with S48 Toxoplasma gondii (Toxovax).

The IgG antibody responses of sheep vaccinated by the subcutaneous injection of live tachyzoites of 'incomplete' strain S48 toxoplasma (Toxovax) were analysed by Western blotting. Antibodies corresponding to a range of tachyzoite antigens (13 to 48 kD) were detected, but the response was dominated by antibody recognising a 30 to 32 kD band. Unvaccinated ewes challenged orally with oocysts of the 'complete' M3 toxoplasma strain had a more complex IgG response that recognised antigens in six dominant bands of similar intensity as those in sheep vaccinated with S48 tachyzoites and then challenged with M3 oocysts. No differences were detected between the antigenic structures of the S48 tachyzoites and RH strain tachyzoites when the antigens were probed with immune ovine sera. Many of the anitgens of the S48 tachyzoites that were recognised had molecular weights similar to those of antigens that have been identified in other strains of toxoplasma.

Animals↗

PubMed1985

Effects of adjuvants and Toxoplasma gondii antigens on immune response and outcome of peroral T. gondii challenge.

Toxoplasma gondii antigens and adjuvants administered parenterally and perorally were tested for their ability to produce serum antibody to T. gondii, to enhance peritoneal microbicidal capacity for T. gondii, and to prevent acquisition of infection by T. gondii ingested subsequently. N-acetylmuramyl-L-alanyl-D-isoglutamine-6-0-stearoyl (MDP) incorporated into liposomes administered intramuscularly to mice with 80 micrograms of T. gondii antigens and the synthetic adjuvant N,N-dioctadecyl-N',N'bis (2-hydroxyethyl) propanediamine (CP 20,961) administered intramuscularly to mice with 80 micrograms of T. gondii lysate antigens produced the highest titres of antibody to T. gondii in sera (i.e., the mean +/- S.D. of the log2 of the reciprocal of the antibody titre to T. gondii measured by Sabin Feldman Dye test was 9 +/- 2 in sera of mice that received T. gondii antigens plus MDP and was 8 +/- 1 in sera of mice that received T. gondii antigens plus CP 20,961). No orally administered preparation produced high titres of serum antibody to T. gondii. None of the preparations which were tested protected mice against infection with T. gondii when cysts containing the parasite were administered by mouth subsequently or enhanced macrophage microbicidal capacity between two and three weeks after the last immunizations. These experiments demonstrate that presence of Toxoplasma antibody (i.e., when log2 of the reciprocal of Toxoplasma antibody titres is 10 or less measured by Sabin Feldman dye test) does not protect mice against dissemination of ingested T. gondii from the gastrointestinal tract. The method of peroral challenge with T. gondii developed for this study is useful for examining effects of other potentially protective regimens in preventing acquisition of ingested T. gondii.

Adjuvants, Immunologic↗

PubMed1985

Congenital toxoplasmic retinochoroiditis in the mouse--the use of the peroxidase anti-peroxidase method to demonstrate Toxoplasma antigen.

The peroxidase anti-peroxidase immunocytochemical staining method has been used to demonstrate Toxoplasma antigen within paraffin-embedded sections of the eyes of mice congenitally infected with Toxoplasma. Intact Toxoplasma tissue cysts were demonstrated within the retina but in no other ocular structure. No endozoites and no extra-cystic antigens were detected by this technique within any of the eyes examined. The possible implications of these findings in relation to the pathogenesis of toxoplasmic retinochoroiditis are discussed.

Animals↗

PubMedDate not supplied

Toxoplasma antibodies in HIV-positive patients from Nairobi.

Sera from 94 patients infected with human immunodeficiency virus (HIV) 1, together with 86 controls, attending the Kenyatta National Hospital, Nairobi were examined for antibodies to Toxoplasma gondii using enzyme immunoassay and latex and dye tests. 54% had Toxoplasma-specific immunoglobulin G (IgG) by dye test. 22% of the HIV-positive group had IgG levels in excess of 180 units/ml (approximating to a dye test titre of 1:1300) compared to 1% of the HIV-negative group. There was no correlation between high levels of IgG and clinical stage of HIV disease or features indicative of active toxoplasmosis. It is proposed that the elevated serum IgG is a reflection of early Toxoplasma reactivation, not necessarily associated with disease.

Acquired Immunodeficiency Syndrome↗

PubMed1984

Immunizing efficacy of Toxoplasma gondii strains isolated from different hosts.

Studies were carried out to determine the fate of virulent Toxoplasma gondii challenge in immune animals. Toxoplasma strains isolated from human, swine, rabbit and cat hosts were used for the primary immunization of mice. Brains were removed at various intervals after the challenge and subinoculated into normal mice. Prior immunization with one of the nine toxoplasma strains enabled the mice either to eliminate or harbour the challenge organisms without loss of virulence. The outcome of challenge infection was dependent on the parasite strain used for the immunization and the time interval between challenge and subinoculation. Mice immunized with strain KSU isolated from a cat eliminated repeatedly administered challenge from 80% of animals. Strain S 162 isolated from a swine eliminated similar challenge from only 20% of animals. The results indicate that the extent of protection against virulent T. gondii can vary widely and is related to the immunogenicity of the original immunizing strain.

Animals↗

PubMed1986

Superoxide dismutase and catalase in Toxoplasma gondii.

Catalase and superoxide dismutase detected in both RH and C strain Toxoplasma gondii tachyzoites were distinctly different in electrophoretic mobility from host cell enzymes. Catalase and superoxide dismutase activity levels were similar in both Toxoplasma strains and showed narrow pH optima around 8.0. Toxoplasma superoxide dismutase was resistant to cyanide but inhibited by azide or peroxide, consistent with an iron-containing enzyme typical of protozoan parasites. These enzymes may play a role in intracellular survival; however, they do not appear to be the basis for differences in virulence to mice.

Animals↗

PubMed1988

The alpha- and beta-tubulins of Toxoplasma gondii are encoded by single copy genes containing multiple introns.

We have studied the fundamentals of gene expression in the protozoan parasite Toxoplasma gondii by analyzing, in detail, the genes encoding alpha- and beta-tubulin. Southern analysis and quantitation studies reveal that, unlike in other organisms studied thus far, both these genes are present as single copies in the haploid Toxoplasma genome. Sequencing of these genes indicates that they both contain multiple introns with conserved 5' and 3' splice site signals. We have found that HeLa cell nuclear extracts are able to accurately splice a Toxoplasma pre-mRNA construct. We have mapped, for the alpha-tubulin gene, the exact site of transcription initiation and the approximate site of poly A addition by primer extension and RNase protection assays. Trans-splicing, as demonstrated in the Kinetoplastida, is not involved in the formation of the mature alpha-tubulin transcript in T. gondii.

Amino Acid Sequence↗