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PubMed1994

Antibodies against toxoplasma in commensal rodents trapped in Riyadh Region, Saudi Arabia.

Toxoplasma gondii, that protozoal parasite which causes toxoplasmosis, pays no respect to boundaries of Zoology and Geography. It has been reported in a large number of birds and mammals including man from nearly all over the world. In Saudi Arabia, the incidence of human infection ranges between 21% and 49.3%. In this paper, the level of antibodies against Toxoplasma in sera of different species of rodents was measured by the indirect haemagglutination tests (IHA). The seropositivities ranged between 12.5% (Mus musculus) and 41.7% (Rattus norvegicus). The overall rate of infection was 35.6%. The role played by rodents in the spreading of the Toxoplasma infection was discussed.

Animals↗
PubMed1993

Cloned human CD4+ cytotoxic T lymphocytes specific for Toxoplasma gondii lyse tachyzoite-infected target cells.

Infection with Toxoplasma gondii is an important cause of morbidity and mortality throughout the world. In immunocompetent hosts, the infection is usually not significant. However, infection occurring in neonates or other individuals with defective cellular immunity (such as recipients of organ allografts or persons with AIDS) may be life threatening. An effective vaccine to prevent toxoplasmosis, or immunotherapy for persons already infected with Tg would be important additions to the therapeutic armamentarium. We cloned toxoplasma-specific CTL from the PBMC of an asymptomatic individual with serologic evidence for prior Tg infection by stimulation with Ag produced from the RH strain of Tg. These CTL were exclusively of the CD3+, CD4+, CD8- surface phenotype, and lysed autologous target cells that had been either pulsed with Toxoplasma Ag, or infected with live tachyzoites. Lysis of target cells was inhibited by incubation of CTL with anti-T cell antibody, or by incubation of target cells with anti-DR antibody or chloroquine. These CTL also lysed target cells either pulsed with Ag derived from C strain Tg or infected with live C strain tachyzoites, indicating cross-reactivity of recognition. Unlike recently reported murine or human CD8+ Tg-specific CTL, which lysed tachyzoites in an extracellular, and hence HLA-unrestricted environment, these CD4+ CTL had no effect on the infectivity of extracellular tachyzoites. CD8+ Tg-specific CTL were not derived from this donor despite several different approaches to their generation. These data confirm previous reports of human Tg-specific CTL, and extend these observations to include CD4+ CTL. These findings suggest that specific immunotherapy directed against Tg, as well as the development of a preventive vaccine, may be possible.

Animals↗
PubMed1994

Analysis of aqueous humor in ocular toxoplasmosis: detection of low avidity IgG specific to Toxoplasma gondii.

Using a modified enzyme-linked immunosorbent assay that included dissociation of antigen antibody complexes with 6M urea solution, we analyzed the avidity of Toxoplasma-specific IgG in aqueous humor and serum samples from 24 patients with toxoplasmic chorioretinitis. As a control, we studied aqueous humor and serum samples from 14 cataract patients without history of uveitis and serum samples from 10 patients with recent primary systemic toxoplasmic infection without ocular lesions. IgG avidity was markedly lower in aqueous humor samples from patients with toxoplasmic chorioretinitis than in serum samples, despite those samples presenting higher levels of Toxoplasma-specific IgG than in serum samples. The detection of the low-avidity Toxoplasma-specific antibodies can offer a valuable aid to make a specific etiologic diagnosis and perhaps contribute to understand the pathogenic mechanisms of ocular toxoplasmosis.

Adolescent↗
PubMed1993

Prevalence of encysted Toxoplasma gondii in raptors from Alabama.

Little is known about the prevalence of encysted Toxoplasma gondii in wild birds. We examined the hearts and breast muscles from 101 raptors for encysted T. gondii. All of the raptors had been submitted for necropsy to the State Veterinary Diagnostic Laboratory, Auburn, Alabama. Tissues were digested in acid-pepsin solution and inoculated into groups of 3-5 laboratory mice. Toxoplasma gondii was isolated from 27 of 101 (26.7%) raptors: 8 of 12 (66.7%) red-shouldered hawks (Buteo lineatus), 13 of 27 (41.1%) red-tailed hawks (Buteo jamaicensis), 1 of 4 (25%) Cooper's hawks (Accipiter cooperi), 1 of 5 (20%) great horned owls (Bubo virginianus), 4 of 15 (26.7%) barred owls (Strix varia), and 1 of 3 (33.3%) kestrels (Falco sparverius). Toxoplasma gondii was not isolated from 3 broad-winged hawks (Buteo platypterus), 3 sharp-shinned hawks (Accipiter striatus), 6 barn owls (Tyto alba), 9 screech owls (Asio otus), a Mississippi kite (Ictinia misisippiensis), 2 golden eagles (Aquila chrysaetos), a bald eagle (Haliaeetus leucocephalus), 4 ospreys (Pandion haliaetus), 4 turkey vultures (Cathartes aura), or 2 black vultures (Coragyps atratus). No significant difference (P > 0.05) in prevalence was detected based on sex using chi-square analysis. Chi-square analysis of the data demonstrated that adult raptors had encysted stages of T. gondii significantly (P < 0.05) more often than did immature raptors.

Age Factors↗
PubMed1993

Experimental Toxoplasma gondii infection in raccoons (Procyon lotor).

Six raccoons (Procyon lotor) without detectable Toxoplasma gondii antibodies were used. Four raccoons were inoculated orally (2 with oocysts and 2 with tissue cysts) with ME49 strain of T. gondii and 2 raccoons were not inoculated with T. gondii. All raccoons remained clinically normal. Raccoons were killed between 59 and 61 days after inoculation and portions of their heart, skeletal muscle, and brain were digested in pepsin solution, and homogenates were bioassayed in mice. Toxoplasma gondii was isolated from all 4 inoculated raccoons; from the heart of 3, skeletal muscles of 2 and the brain of none. All 4 inoculated raccoons developed antibody titers > or = 1:1,600 in the modified direct agglutination test (MAT) using whole formalinized tachyzoites. Toxoplasma gondii antibody titers of the raccoons not inoculated with T. gondii remained < 1:25, and T. gondii was not isolated from their tissues. It was concluded that muscle tissue from multiple sites including the heart was the tissue of choice for conducting parasitologic surveys for T. gondii in raccoons. Evaluation of the sera of the experimentally infected raccoons in the Sabin-Feldman dye test, latex agglutination test, and the indirect hemagglutination tests indicated that the MAT detected antibodies faster and in higher titers than did the other serological tests.

Agglutination Tests↗
PubMed1993

Comparative study of three tests (indirect haemagglutination, direct agglutination, and indirect immunofluorescence) for detection of antibodies to Toxoplasma gondii in pregnant women.

Sera of 600 asymptomatic pregnant women were tested by IHAT for Toxoplasma antibodies. The positive reactors were further tested by IFAT and direct agglutination test (DAT). The prevalence of Toxoplasma antibodies was found to be 27.3% by IHAT, and 58.5% of those found positive were also positive by IFAT, while only 51.8% of them were positive by DAT with 71.34% degree agreement between both tests. So, IFAT was found to be more sensitive than DAT in reference to IHAT and is recommended as a confirmatory test for those found positive on screening by IHAT, DAT, compared to IFAT, gave 69.7% sensitivity and 73.5% specificity. Results support previous findings that IHAT, IFAT and DAT measure different antibodies of Toxoplasma gondii.

Agglutination Tests↗
PubMed1977

Experimental toxoplasmosis in mice and rabbits. Virulence and cyst formation of Toxoplasma gondii.

Avirulent Toxoplasma gondii were made virulent by passages in mice, and then attenuated by storage. In contrast to the avirulent parasites, attenuated organisms did not appear to form cysts in mice and rabbits, although parasites could be isolated from such animals as long as three months after their inoculation. Rabbits infected with parasites of attenuated virulence had high antibody levels, and survived challenge with virulent Toxoplasma gondii. Cysts were not detected in the brains of such rabbits following this second infection. By following the generation of Toxoplasma gondii in mouse peritoneal cavities, it was found that attenuated parasites resembled avirulent more than virulent organisms. Although the effect of attenuation was mainly on the parental generation of parasites, some genetic effect seemed to be involved as well.

Animals↗
PubMed1993

Primary structure of the dihydrofolate reductase-thymidylate synthase gene from Toxoplasma gondii.

We have determined the primary genomic and cDNA sequences encoding the bifunctional dihydrofolate reductase-thymidylate synthase (DHFR-TS) enzyme of the protozoan parasite Toxoplasma gondii (dihydrofolate reductase, EC 1.5.1.3; thymidylate synthase EC 2.1.1.45). The DHFR-TS gene of T. gondii (strain RH) spans more than 6 kilobases of genomic DNA. Unlike the DHFR-TS genes of other protists, sequences encoding the Toxoplasma protein are interrupted by numerous intervening sequences. Analysis of processed T. gondii DHFR-TS cDNAs reveals a single open reading frame of 1830 nucleotides, predicting a 610-amino acid protein of molecular mass of 69 kilodaltons. Because its nucleotide composition and codon usage are roughly comparable to those observed in "higher" eukaryotes, the Toxoplasma DHFR-TS sequence is particularly useful for assessing evolutionary relationships between eukaryotic species. The predicted amino acid sequence for the DHFR-TS protein shows conservation of the major structural features identified in other DHFR and TS enzymes, while revealing certain differences which may be exploited for the design of novel antifolates for treatment of toxoplasmosis associated with AIDS.

Amino Acid Sequence↗
PubMed1996

Production of nitric oxide (NO) is not essential for protection against acute Toxoplasma gondii infection in IRF-1-/- mice.

Production of nitric oxide (NO) by macrophages is important for the killing of intracellular pathogens. IFN-gamma and LPS stimulate NO production by transcriptional up-regulation of inducible nitric oxide synthetase (iNOS). In the present study we used mice with a targeted disruption of the IFN regulatory factor-1 gene (IRF-1-/-) to investigate the importance of NO in the host immune response against Toxoplasma gondii, a major cause of infection in newborns and those with AIDS. IRF-1-/- mice were more susceptible to acute Toxoplasma infection, and treatment with either exogenous IFN-gamma or in vivo neutralization of endogenous IFN-gamma had little effect on their susceptibility to infection. However, administration of exogenous IL-12 was able to prolong survival even when IFN-gamma was depleted. An in vivo depletion study suggested that the mechanism of this protective response is mediated in part by CD4+ T cells. The administration of IL-12 could not overcome the inhibition of lymphoproliferative response in T. gondii-infected mice and treatment with N-monomethyl-L-arginine (L-NMMA), a nitric oxide synthase (iNOS) antagonist in vitro was unable to reverse the immunosuppression. In response to Toxoplasma infection, splenocytes from IRF-1-/- mice exhibited increased production of IL-10 as well as a 30-fold increase in its message expression. These studies indicate that NO may not be essential for host immunity to the parasite, and moreover that IL-12 appears to induce an IFN-gamma-independent mechanism of protection against this opportunistic pathogen.

Animals↗
PubMed1996

Infectivity of low numbers of Toxoplasma gondii oocysts to pigs.

To define the infectiousness of the VEG strain of Toxoplasma gondii, 42 pigs were fed doses estimated at 10, 1, or < 1 mouse infective oocysts. They were killed 38-99 days after inoculation and 50 g of tissues from their tongue, heart, and brain were individually homogenized in acidic pepsin solution and bioassayed in mice. Pools of brain, heart, tongue, and skeletal muscle (total 500 g) were bioassayed in cats. Toxoplasma gondii was isolated by bioassays in mice and in cats from 13 of 14 pigs fed 10 oocysts, 13 of 14 pigs fed 1 oocyst, and 4 of 14 pigs fed "less than" 1 oocyst, indicating high infectivity of VEG strain of T. gondii to pigs. All infected pigs developed modified agglutination test antibodies (> 1:50). Control pigs (n = 6) remained seronegative (< 1:20) and T. gondii was not isolated from their tissues. Toxoplasma gondii was isolated from tongues of 27 (93%), brains of 21 (72%), and hearts of 13 (45%) of 29 experimentally infected pigs by bioassay in mice. The number of T. gondii-positive mice after inoculation of tongue, brain, and heart from infected pigs was 240 (80%), 84 (28%), and 36 (12%) of 300 mice inoculated with each organ, respectively. Thus, the VEG strain of T. gondii was localized more often and in higher numbers in the tongue than in the brain and the heart of pigs. The apparent muscle localization after infection with the low dose of the VEG strain of T. gondii agrees with other studies in livestock that suggest T. gondii is more neurotropic in mice than in livestock.

Animals↗
PubMed1996

[Susceptibility of Sigmodon hispidus (Rodentia: Cricetidae) to Toxoplasma gondii (Eucoccidia: Sarcocystidae)].

Sigmodon hispidus, a cotton rat, was inoculated with tachyzoites or oocysts of Costa Rican strains of Toxoplasma gondii to demonstrate the resistance to this parasite, as compared with mice, hamster and white rat infection. Susceptibility to tachyzoite inoculation was higher in this animal than in white rats but lower than in the other animals. Independent to the Toxoplasma strain studied, oocyst infection was less lethal for S. hispidus when compared with mice and hamsters; the results were similar to those observed for white rats. There is a probable participation of this wild animal in the natural Toxoplasma life cycle.

Animals↗
PubMed1997

Expression pattern and cellular origin of cytokines in the normal and Toxoplasma gondii-infected murine brain.

In the normal brain, low levels of cytokines are observed, whereas inflammatory disorders of the central nervous system are characterized by an up-regulation of cytokine production. The cellular sources for cytokines in the central nervous system are largely undefined. In the present study, we have analyzed intracerebral cytokine production in normal and Toxoplasma gondii-infected mice using immunohistochemistry, in situ hybridization, flow cytometry of brain-derived leukocytes, and reverse transcriptase polymerase chain reaction detection in various subpopulations of inflammatory cells. In the normal brain, neurons and choroid plexus epithelia expressed interleukin (IL)-1 beta and IL-10. Microglia/macrophages produced IL-1 beta, IL-10, and tumor necrosis factor-alpha In Toxoplasma encephalitis, these cell types exhibited increased levels of the respective cytokines. In addition, microglia/macrophages showed a de novo expression of inducible nitric oxide synthase. CD4+ and CD8+ T cells, which were recruited to the brain, produced IL-2, IL-10, tumor necrosis factor-alpha, and interferon-gamma. IL-4 was exclusively detectable in CD4+ T cells, whereas CD8+ T cells showed expression of IL-1 beta. As chronic Toxoplasma encephalitis was not associated with neuronal degeneration and an up-regulation of neurotrophic factors, some cytokines may also exert neurotrophic and/or neuroprotective properties.

Animals↗
PubMedDate not supplied

Increasing toxoplasma seropositivity in women with bad obstetric history and in newborns.

BACKGROUND: Most infants with congenital Toxoplasma gondii infection have no symptoms at birth but few may develop retinal diseases or neurological abnormalities later in life. The presence of significant titres of antitoxoplasma antibodies in women in the reproductive age group indirectly indicates that Toxoplasma gondii is the cause of such congenital abnormalities and also sporadic abortions in some women. METHODS: We did a retrospective analysis of antitoxoplasma antibodies detected by indirect haemagglutination assay, in women with bad obstetrical history and in newborns clinically suspected of congenital toxoplasmosis during 1981-91. RESULTS: A significant increase in seropositivity in women and newborns was seen during 1989-91 as compared to 1981-88. More seropositive patients were recorded between April-June and October-December. However, no significant correlation could be observed between rising incidence of seropositivity and the seasonal distribution or age of women. CONCLUSION: Epidemiological studies are required to ascertain the reason for the increasing trend of toxoplasma seropositivity and to suggest appropriate control strategies as it is possible to prevent congenital infection.

Adolescent↗
PubMed1996

Seroepidemiological study of Toxoplasma infection in central and western regions in Nepal.

The present study was carried out to ascertain the seroprevalence rate in different geographical areas in Central and Western Regions in Nepal. A total of 1,237 serum samples collected from Nuwakot (217), Kathmandu valley (402) and Chitawan (159) districts in Central Region, and Mustang (143), Surkhet (64) and Banke (252) districts in Western Region in Nepal were included in this study. Toxoplasma antibodies were detected by micro-latex agglutination (MLA) and enzyme linked immunosorbent assay (IgM-ELISA) methods. The seropositive rate in Central and Western Regions were found to be 48% and 49%, respectively; with an overall positive rate of 48 percent. Districtwise, the seropositive rate in Nuwakot, Kathmandu valley, Chitawan, Mustang, Surkhet and Banke districts were 38, 46, 64, 51, 67 and 44%, respectively. Interestingly, the relatively newly inhabited Surkhet district in Western Region and Chitawan district in Central Region showed significantly higher seropositive rate compared with those of two other districts in the respective Regions (p < 0.05). Ethnically, Tibeto-Burmans showed higher seropositive rates in Central Region (p > 0.05). In contrast, Indo-Aryans showed higher seropositive rate in Western Region (p > 0.05). Age related increase in seropositivity was observed only in Central Region. One percent of Toxoplasma antibody positive samples also showed Toxoplasma IgM antibody positivity.

Adult↗
PubMedDate not supplied

[The spread of antibodies to cytomegalovirus and Toxoplasma among donors of blood components].

The spread of IgG antibodies to cytomegalovirus and Toxoplasma in the blood sera of 323 donors of hemocomponents was studied. Among young males in the northwestern region of Russia three fourths were found to be seropositive to cytomegalovirus and one third, to Toxoplasma. In older ages the proportion of seropositive persons somewhat increased. In donors with blood group O (I) antibodies to cytomegalovirus occurred almost twice as often (91%) as in donors with blood group AB (IV) (47%). Among donors with blood group AB (IV) the proportion of persons seropositive to Toxoplasma (54%) was twice as great as that among donors with blood group O (I) (27%).

ABO Blood-Group System↗
PubMed1997

[Lymphadenopathy caused by Toxoplasma in an intramammary lymph node: role of molecular biology in the diagnosis].

We describe a case of Toxoplasma gondii lymphoadenopathy in an intramammary lymph node in a 22 year old woman. Clinical evidence and ultrasound were suggestive for fibroadenoma, while cytology on fine needle aspiration suspected a lymphomatous lesion. The pathological examination demonstrated a lymph node with granulomatous foci with epithelioid histiocytes, consistent with Toxoplasma gondii lymphadenopathy. The pathological finding was confirmed by serological tests and by PCR (Polymerase Chain Reaction) using specific primers designed on ribosomal 18s DNA sequence of Toxoplasma gondii. The aim of this work is to emphasize the role of molecular biology techniques as an aid to pathological diagnosis in parasite diseases.

Adult↗
PubMed1997

[Detection of IgA antibodies as important markers of acute primary infection with Toxoplasma gondii].

The diagnosis of Toxoplasma gondii infection is currently based on immunological tests, but tests for IgM and IgG antibodies alone are often insufficient to estimate the risk of active disease, especially during pregnancy and in immunodeficient patients. Classically the study of anti-toxoplasma immunity involves titration of IgG antibodies, which reflect immunity to the parasite, and IgM antibodies which of present, reveal acute infection. However, technical advances have shown the limitations of these tests as tests for IgM can be positive because of residual specific IgM or even in subjects free of acute infection due to the existence of natural interfering IgM. In addition, IgM can be absent in children with congenital toxoplasmosis or subjects with secondary reactivation. The purpose of our study was to evaluated of IgA antibodies to T. gondii in serum samples which were positive in screening test. Our results confirm the diagnostic value of testing for anti-toxoplasma IgA antibodies. These antibodies are absent in uninfected subjects and are detected rapidly after primary infection. The determination of IgA complements IgM determination for the diagnosis of toxoplasmosis.

Adult↗
PubMed1998

[A case of congenital toxoplasmosis confirmed by detection of Toxoplasma gondii in placenta].

We report a case of congenital toxoplasmosis with a prenatal diagnosis of fetal hydrocephalus. A CT scan performed at birth revealed ventricular dilation with calcification. The serum and CSF Toxoplasma specific IgM were elevated. The diagnosis was confirmed by the presence of Toxoplasma cysts in the placenta, and detection of the Toxoplasma SAG1 gene by a polymerase chain reaction (PCR) (placenta, positive; CSF, negative). Signs of active central nervous system infection, such as the decreased CSF glucose, and elevated CSF protein, neuron specific enolase and LDH, resolved after initiation of treatment with pyrimethamine and sulfazoxine. A PCR test using the placental tissue may be useful for the rapid diagnosis of congenital toxoplasmosis.

Adult↗