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PubMed2005

Decreased level of novelty seeking in blood donors infected with Toxoplasma.

OBJECTIVES: Toxoplasma gondii, a parasitic protozoan, infects about 30 - 60% of people worldwide. Toxoplasma is known to induce behavioral changes and an increase of dopamine in mice. The presence of anti-Toxoplasma antibodies (latent toxoplasmosis) is also a risk factor for schizophrenia. Latent toxoplasmosis in men (male soldiers) is associated with lower novelty seeking. As the novelty seeking is supposed to negatively correlate with level of dopamine, the observed effect was interpreted as indirect evidence of increased dopamine levels in subjects with toxoplasmosis. However, it is also possible that the observed effect was caused by association of both novelty seeking and Toxoplasma infection with a third factor, e.g. size of place of residence. METHODS: Personality profile of 290 blood donors (205 men and 85 women) were measured by Cloninger's TCI (Temperament and Character Inventory) and their blood samples were assayed for the presence of anti-Toxoplasma antibodies. Difference between Toxoplasma-infected and Toxoplasma-free subjects was tested with ANCOVA method with gender, size of place of residence, and age as covariates. RESULTS: The present analysis revealed that lower novelty seeking was associated with latent toxoplasmosis both in men and women. The effect of infection on novelty seeking remained significant even after adjustment for size of place of residence (p<0.01). CONCLUSION: Decreased novelty seeking in Toxoplasma-infected subjects have been already confirmed in three independent populations (male soldiers and male and female blood donors). These findings suggest that the local inflammation-induced increase in dopamine in the brain of infected subjects can represent a missing link between toxoplasmosis and schizophrenia.

Adult↗

PubMed1993

Prevalence of Toxoplasma infection in a cohort of homosexual men at risk of AIDS and toxoplasmic encephalitis.

The purpose of this study was to characterize the epidemiologic, clinical, and laboratory parameters of a cohort of men at risk of AIDS-associated toxoplasmic encephalitis. One hundred seventeen (11%) of the 1,073 participants at the time of enrollment into the Chicago Multicenter AIDS Cohort Study (MACS) were seropositive for Toxoplasma antibodies. Significant differences in prevalence of antibodies between African-American, Hispanic, or white men were not observed (p = 0.49). One hundred one (86%) of the 117 antibody-positive participants had at least one follow-up serology performed and 6 (6%) of the 101 had a significant rise in IgG antibody titer on subsequent visits. Five of six participants with a significant rise in titer were also seropositive for HIV-1 at entry or seroconverted during the study. A trend toward higher IgG Toxoplasma titers and prevalence of IgM antibodies in participants seropositive for HIV-1 was observed, but the differences did not reach statistical significance. There was no evidence that the presence of Toxoplasma infection predisposed to development of CD4+ depletion or AIDS. None of the 183 individuals in the cohort who developed AIDS and who were seronegative for Toxoplasma antibodies developed toxoplasmic encephalitis. In contrast, of the 13 persons who developed AIDS and who were positive for Toxoplasma antibodies, 5 (38%) developed toxoplasmic encephalitis. Prevalence of Toxoplasma antibodies in the MACS population was independent of HIV-1 serostatus. Toxoplasma infection does not appear to predispose to progression of HIV-1 infection. The risk of development of toxoplasmic encephalitis in persons with AIDS and chronic Toxoplasma infection may have been underestimated by previous retrospective studies.

Acquired Immunodeficiency Syndrome↗

PubMed1987

Activation of rat alveolar macrophages by gamma interferon to inhibit Toxoplasma gondii in vitro.

We have investigated the effects of murine interferons on the ability of rat alveolar macrophages (AM) to inhibit the proliferation of the intracellular protozoan Toxoplasma gondii. This activity was determined by measuring suppression of 3H-uracil uptake into the Toxoplasma and by microscopic enumeration of the intracellular organisms. Recombinant gamma interferon (rMulFN-gamma), but not alpha/beta interferon (IFN-alpha/beta) was able to activate AM for antimicrobial activity in vitro. Maximum activation was achieved by incubation with 50-200 units/ml rMulFN-gamma and the activity was lost at one unit/ml. The highest levels of activation were obtained when macrophages were incubated with interferon for 48-72 h prior to the challenge with Toxoplasma organisms. Activation could still be obtained, however, when the interferon was added to the cultures as late as 2 h after the phagocytosis of Toxoplasma. Neither MDP nor low concentrations (1-1-ng/ml) of S. typhosa lipopolysaccharide (LPS) were able to activate these cells to inhibit the growth of Toxoplasma. Phagocytosis of Toxoplasma by AM did not result in the release of O2-, in fact the spontaneous release of O2- by these cells was inhibited by Toxoplasma. This inhibition was reversed by preincubation of the cells with rMulFN-gamma.

Acetylmuramyl-Alanyl-Isoglutamine↗

PubMed1983

Distribution of cysts and tachyzoites in calves and pregnant cows inoculated with Toxoplasma gondii oocysts.

Sixteen calves and 6 cows were each inoculated with 100 000 infective oocysts of the GT-1 strain of Toxoplasma gondii. Cattle were necropsied between 3 and 287 days post-inoculation (DPI) and their tissues were inoculated into mice or fed to Toxoplasma-free cats for the detection to Toxoplasma in bovine tissues. Ten to 10 000-fold more T. gondii were recovered from small intestine and mesenteric lymph nodes of calves at 3 and 6 DPI than from lungs and liver, and the number of T. gondii in bovine tissues was reduced 1000-fold between 6 and 8 DPI. By using the Pepsin digestion technique, or feeding tissues to Toxoplasmas-free cats, it was demonstrated that T. gondii encysted in bovine tissues as early as 11 DPI and persisted as late as 287 DPI. More Toxoplasma gondii cysts occurred in livers than in many other bovine tissue. Of the 6 cows inoculated at 95--155 days after breeding, 5 delivered normal calves and T. gondii was isolated from only one of these calves. One cow was barren. Toxoplasma gondii was not isolated either by mouse inoculation or by feeding cats tissues from 2 cows killed 132 and 190 DPI. Toxoplasma gondii was not isolated in mice inoculated with tissues of cows killed 98 and 109 DPI, but cats fed on bovine tissues shed T. gondii oocysts. The organism, however, was isolated in mice inoculated with the mesenteric lymph nodes of 1 of the 2 cows killed 162 and 168 DPI, and from the small intestine of the other. Cats fed tissues of these cows later shed T. gondii oocysts.

Animals↗

PubMed1996

Human V delta 2+ gamma delta T-cell tolerance to foreign antigens of Toxoplasma gondii.

Little is known about the mechanisms involved in human gammadelta T-cell tolerance to self or to foreign antigens. Patients with congenital toxoplasmosis offer a unique opportunity to examine Vdelta2+ gammadelta T-cell tolerance. Analysis of gammadelta T cells in patients with congenital toxoplasmosis revealed evidence for anergy of these cells with or without clonal Vdelta2+ gammadelta T-cell expansion in the acute phase of the Toxoplasma infection. T cells in general were unresponsive and did not proliferate upon exposure to mitogens or to Toxoplasma lysate antigens or in response to live Toxoplasma-infected cells when the congenitally infected infants were 1 month of age, and they exhibited selective anergy to Toxoplasma lysate antigens and live Toxoplasma-infected cells when the infants were aged 5 months. During the chronic phase of congenital toxoplasmosis in the patients who were more than I year of age, the repertoires of the gammadelta T-cell receptors were found to be within normal ranges. In addition, in the chronic phase, the gammadelta T cells proliferated and secreted gamma-interferon in response to exposure to live Toxoplasmia-infected cells. By contrast, alphabeta T cells remained anergic. Vdelta2+ gammadelta T cells have been considered to undergo extrathymic maturation and thus to be subject to development of peripheral tolerance. Our findings indicate that Vdelta2+ gammadelta T-cell tolerance was lost in these infected infants earlier than alphabeta T-cell tolerance. These findings suggest that gammadelta T cells play a role in protection against Toxoplasma gondii in the chronic phase when congenitally infected children are more than 1 year of age, especially in those in whom alphabeta T cells continue to exhibit deficits in specific immune responses to Toxoplasma antigens.

Acute Disease↗

PubMed1985

Serologic diagnosis of toxoplasmosis with emphasis on the detection of Toxoplasma-specific immunoglobulin M antibodies.

Commercially available kits were used for the detection of Toxoplasma-specific IgM antibodies. False positive IgM results were observed in whole sera containing Toxoplasma-specific antibodies together with rheumatoid factor when tested by immunofluorescence (IFA). False negative IgM results occurred in whole sera containing competing levels of Toxoplasma-specific IgG antibodies, as indicated by the IFA:IgM-M ratio. False positive and false negative IgM results often occurred when whole sera were tested. These false reactions were eliminated by fractioning IgM from IgG using the Isolab's IgM Isolation System. All five sera in this study with an IFA titer to Toxoplasma of greater than or equal to 1:16,384 also contained Toxoplasma-specific IgM antibodies. This suggests that sera with high titers to Toxoplasma should be tested for Toxoplasma-specific IgM antibodies.

Antibody Specificity↗

PubMed1991

Toxoplasma serology, parasitemia and antigenemia in patients at risk for toxoplasmic encephalitis.

In order to further characterize the pathogenesis of Toxoplasma gondii infection in patients with AIDS and AIDS-related complex (ARC), a cohort of HIV- and Toxoplasma-infected individuals were identified and prospectively followed. Four hundred and 10 HIV-infected individuals followed in the San Francisco General Hospital AIDS Clinic were screened for antibodies to Toxoplasma between November 1986 and November 1988. Of the 67 (16%) individuals seropositive for Toxoplasma antibodies, 33 (49%) were followed monthly for a mean duration of 7.5 months. One hundred and 11 follow-up blood samples were obtained in order to determine Toxoplasma serology and the incidence of parasitemia. In general, Toxoplasma immunoglobulin (Ig) G antibodies remained stable over time. Detection of Toxoplasma antigenemia and parasitemia was uniformly negative, including those specimens obtained from two individuals within 45 days of their developing toxoplasmic encephalitis.

Animals↗

PubMed1986

Strain differences of interferon-generating capacity and resistance in toxoplasma-infected mice.

To explore a possible correlation between susceptibility to Toxoplasma and interferon (IFN)-generating capacity in mice, we compared the levels of serum IFN induced by stimulation with Toxoplasma lysate antigen (TLA) in different strains of Toxoplasma-infected and uninfected mice. Injection of TLA into five strains of mice with chronic Toxoplasma infection resulted in the release of considerable amounts of IFN into the circulation. Most of these IFN activities were acid labile and not neutralized by sheep antiserum against mouse IFN-alpha/beta, indicating that IFN-gamma was the dominant form produced in this system. In contrast, the majority of IFN induced in uninfected mice was characterized as IFN-alpha/beta by their acid stability and antigenicity. The response of IFN production in Toxoplasma-infected and uninfected mice varied quantitatively depending on the mouse strains examined. C57BL/6 mice were found to be the best producers of both IFN-alpha/beta and IFN-gamma, while BALB/c mice were consistently poor producers of both IFN populations. A/J, DBA/2, and C3H/He mice could be roughly classified as intermediate producers of both IFN populations. C57BL/6 and C3H/He mice showed a significant prolongation of mean survival time following primary or secondary infection with Toxoplasma compared to that of BALB/c mice. However, there was no direct correlation between the susceptibility to Toxoplasma and the levels of serum IFN.

Acute Disease↗

PubMed1998

Seroprevalence of toxoplasma antibodies among the antenatal population in Bangladesh.

OBJECTIVE: To determine the seroprevalence of toxoplasma antibodies toxoplasma IgG and toxoplasma IgM) among an antenatal population in a hospital of Bangladesh. METHODS: Sera from 286 pregnant women were tested for toxoplasma IgG antibody by applying enzyme linked immunosorbent assay (ELISA) technique. Among the 286 sera, 88 sera were randomly selected and tested for toxoplasma IgM applying ELISA. RESULTS: Among 286 patients 110 (38.5%) were positive for toxoplasma IgG antibody and among 88 patients only one (1.1%) was positive for toxoplasma IgM. The seroprevalence gradually increased with age and parity. The seroprevalence of antibody was higher among the women in poor (53.0%) than the upper socio-economic class (22.0%) and among the women with jobs (55.0%) than the housewife group (35.0%). CONCLUSION: This study shows that toxoplasmosis is endemic in Bangladesh and also affecting pregnant women. There is need for further detailed studies on toxoplasmosis and its influence on perinatal morbidity and mortality.

Adolescent↗

PubMed1986

Mechanisms of killing of Toxoplasma gondii by rat peritoneal macrophages.

Rats are resistant to Toxoplasma infection, and macrophages are thought to mediate this resistance. We performed a series of experiments to investigate the mechanism of the anti-Toxoplasma activity of resident rat peritoneal macrophages. Resident rat peritoneal macrophages killed more than 90% of ingested Toxoplasma gondii in vitro. This capacity was reduced progressively with the prolongation of culturing of macrophages in vitro before challenge with T. gondii. Exhaustion of the respiratory burst of macrophages with phorbol myristate acetate impaired their ability to kill and limit the replication of T. gondii. Histidine and diazabicyclooctane, presumed scavengers of singlet oxygen, were the only members of a battery of scavengers of metabolites of the respiratory burst that impaired the anti-Toxoplasma activity of macrophages. Ingestion of heat-killed Candida albicans by macrophages reduced large amounts of intracellular Nitro Blue Tetrazolium dye, whereas little dye was reduced by the ingestion of T. gondii. Challenge of macrophages with T. gondii released no detectable superoxide anion, as measured by the reduction of ferricytochrome c, whereas stimulation of macrophages with phorbol myristate acetate or ingestion of heat-killed Candida by macrophages released abundant superoxide anion. These data are consistent with the contributions of oxygen-dependent and oxygen-independent mechanisms to the anti-Toxoplasma activity of rat peritoneal macrophages. In addition, neonatal rats are known to be susceptible to Toxoplasma infection in vivo. However, resident neonatal rat peritoneal macrophages ingested and killed T. gondii to the same extent as did adult macrophages. Thus, the susceptibility of neonatal rats to Toxoplasma infection probably resides in other aspects of macrophage function or the immune response.

Animals↗

PubMed1981

Immunoglobulin M-immunosorbent agglutination assay for diagnosis of infectious diseases: diagnosis of acute congenital and acquired Toxoplasma infections.

An immunoglobulin M (IgM)-immunosorbent agglutination assay (IgM-IS-AGA) was negative in all sera from individuals negative in the Sabin-Feldman dye test, in sera from individuals with chronic Toxoplasma infection, and in cord blood samples from uninfected infants. In contrast, all sera that were obtained from individuals with a recent history of acute Toxoplasma infection and from infants with congenital Toxoplasma infection and that were positive in both the dye test and the IgM-indirect fluorescent-antibody (IgM-IFA) test were positive in IgM-ISAGA. A total of 21 (67.7%) of 31 sera that were negative in the IgM-IFA test, despite being obtained from individuals with recently acquired Toxoplasma infection, and 8 (72.7%) of 11 sera that were negative in the IgM-IFA test and obtained from infants with congenital Toxoplasma infection were positive in IgM-ISAGA. The presence of rheumatoid factor, antinuclear antibodies, or both did not cause false-positive results in the IgM-ISAGA but did so in the IgM-IFA test. Thus, IgM-ISAGA in both more sensitive and more specific than the IgM-IFA test for detection of IgM antibodies to Toxoplasma gondii and, therefore, for the diagnosis of acute congenital and acquired Toxoplasma infections.

Acute Disease↗

PubMedDate not supplied

Toxoplasma lymphadenitis. Analysis of cytologic and histopathologic criteria and correlation with serologic tests.

OBJECTIVE: To identify cases of Toxoplasma lymphadenitis by light microscopic examination of fine needle aspiration cytology (FNAC) smears and paraffin sections and to correlate the result with those of serologic tests. STUDY DESIGN: The study group consisted of 19 cases of Toxoplasma lymphadenitis, 7 of which were diagnosed by FNAC, 9 on excision biopsy and 3 on FNAC followed by biopsy. Nineteen cases of reactive lymphadenitis, tuberculosis and infectious mononucleosus composed the control group. Sera from all 38 patients were screened for antibodies to Toxoplasma. RESULTS: Eleven of 19 cases (58%) of Toxoplasma adenitis had very high titers of antibody (> 300 ELISA units/ml), and 6 cases (31%) had antibody titers in a range suggestive of active infection (210-300 ELISA units/mL) and required demonstration of rising titers. Overall, 89% of patients with Toxoplasma lymphadenitis showed significant levels of antibody. All patients from the control group showed consistently low levels of antibody to Toxoplasma. CONCLUSION: Though serologic tests are mandatory for the diagnosis of Toxoplasma lymphadenitis, a high index of suspicion can be obtained by means of light microscopy alone.

Adolescent↗

PubMed2004

The roles of cats and dogs in the transmission of Toxoplasma infection in Kuna and Embera children in eastern Panama.

OBJECTIVE: To examine the relationship between antibody status and various hypothesized risk factors for Toxoplasma gondii infection among two different Amerindian populations in eastern Panama. Following up on earlier research that we conducted, we now explore the role of dogs in the natural transmission of Toxoplasma, the role that dogs play in promoting transmission, the interactive effect of cats and dogs, and the accessibility of infective material to children. METHODS: In 1991, 10 Panamanian medical students conducted interviews and took blood samples from 760 Kuna and Embera children aged 2 through 12 years in the Upper Bayano River Basin and the San Blas Islands. Serologic assays were performed using direct agglutination. The data analyses in the 1990s included univariate, bivariate, and multivariate analyses, without regard to data on dogs. Further bivariate and multivariate analyses were performed in 2003 to examine the contribution of dogs. RESULTS: In communities with high Toxoplasma antibody prevalence in children, logistic regression suggested that the factors predictive of antibody presence were: compacted soil floors of huts (P = 0.001), having a dog (P = 0.038), and the interviewer seeing a cat in the house (P = 0.049). Our results suggest that the villagers' dogs play a significant role in facilitating the transmission of Toxoplasma gondii to humans, most often in the presence of cats in the houses, and only in those communities with higher Toxoplasma seroprevalence in children. CONCLUSIONS: Dogs may act as mechanical vectors, by rolling in foul-smelling substances and by ingesting fecal material. In areas of high Toxoplasma prevalence in children and where dogs and cats are plentiful, immunocompromised individuals and pregnant women should be warned of the possibility of acquiring Toxoplasma gondii from dogs as well as from soil contaminated by cats. People should be encouraged to wash their hands after contact with soil, dogs, or cats as well as before eating.

Animals↗

PubMed1975

Method for differentiation of nonspecific from specfic toxoplasma IgM fluorescent antibodies in patients with rheumatoid factor.

In a study performed to define the prevalence of false positive toxoplasma IgM-IFA test results in sera containing RF, 8 (19.5%) of 41 sera which were positive for RF were positive in the toxoplasma DT and conventional toxoplasma IFA test. Three of these eight were also positive in the toxoplasma IgM-IFA test and in two, the results were considered to be false positives. Of the 33 sera remaining which were positive for RF but negative in both the DT and conventional IFA test, three were positive in the toxoplasma IgM-IFA test. Of 51 sera from patients with suspected rheumatoid arthritis or other collagen vascular disorders, all of which were negative when tested for RF, none was positive for toxoplasma IgM antibodies in the IgM-IFA test. Sera from 15 adults with the acute lymphadenopathic form of toxoplasmosis and 13 infants with congenital toxoplasmosis were tested for the presence of RF. Whereas none of the sera from the acquired cases had demonstrable RF, two of the congenital cases had RF, and their titers were both 1:320. False positive IgM-IFA test results became negative after treatment of sera with heat-aggregated IgG. In contrast, IgM-IFA test titers in cases of acute congenital or acquired toxoplasmosis were unaffected by this treatment. Thus, treatment with heat-aggregated IgG can be used to differentiate false positive IgM-IFA test titers due to RF from those due to specific IgM toxoplasma antibody.

Agglutination Tests↗

PubMed1998

Antibody reaction of human anti-Toxoplasma gondii positive and negative sera with Neospora caninum antigens.

Anti-Neospora caninum antibody was detected in anti-Toxoplasma gondii positive and negative human sera by ELISA, western blot and immunofluorescence assay (IFA). Twelve cases out of 172 (6.7%) Toxoplasma-positive sera cross-reacted with both T. gondii and N. caninum antigens, and one out of 110 Toxoplasma-negative sera reacted with N. caninum antigen by ELISA. By western blot, all 12 sera reacted with T. gondii antigens with various banding patterns but specifically at 30 kDa (SAG1) and 22 kDa (SAG2) bands. With N. caninum antigen, the number of reactive bands was reduced, however a 43 kDa band reacted in three cases in Toxoplasma-positive sera in addition to one in Toxoplasma-negative control sera. All sera of the Toxoplasma-positive group labeled surface membrane of T. gondii, but reacted differently with N. caninum. Fluorescence was detected in surface membrane, subcellular organelles, or both in N. caninum. And one case in the Toxoplasma-negative group also reacted with N. caninum strongly in subcellular organelles. This suggested that the antibody against N. caninum may be present in human sera although the positive rate was very low in this study. The possibility of human infection with N. caninum remains to be evaluated further.

Animals↗

PubMed1989

Toxoplasma gondii: a simple method for titration of infectivity with monolayer cells.

A simple method for assessing the infectivity of Toxoplasma gondii using primary cultured monolayer cells has been devised. Statistic analysis important for interpreting the results of such experimentation was made. In this method, the number of intracellular toxoplasmas and the percentage of confluency of the monolayer were measured. The latter value was used for conversion of the number of intracellular toxoplasmas per unit area to the percentage of infective toxoplasmas. A linear dose-response relationship between the number of intracellular toxoplasmas per unit area and that of toxoplasmas inoculated was demonstrated with primary cell monolayers from the lungs of two-day old inbred golden hamsters and the kidneys of newborn mice and newborn Wistar Imamichi strain rats. On the average, 37% of the toxoplasma organisms harvested from the peritoneal exudate of mice on the third or fourth day of infection were found to be infective. This value compares very favorably with the value 40% reported previously.

Animals↗

PubMed2001

Risk of Toxoplasma gondii infection in slaughterhouse workers in Kitakyushu City.

To clarify the risk of Toxoplasma gondii infection among slaughterhouse workers, we investigated Toxoplasma antibody in workers and swine in the meat center of Kitakyushu City and discussed the result from the standpoint of working conditions. Among 67 slaughterhouse workers, 22 were positive for Toxoplasma antibody (positive rate, 32.8%), while among 208 swine, 19 were positive (positive rate, 9.1%). When classified by ages of workers, positive rates in workers were 0% at the age of 30 or less and around 40% at the age of 31 and over. Especially, positive rate became as high as 66.7% in workers aged 61 and over. Positive rates for Toxoplasma antibody in workers classified by duration of employment were 25% for 5 years or less and 41.5% for 6 years and over. Moreover, there was no difference in positive rates of Toxoplasma antibody between swine slaughterers (positive rate, 32.4%) and cattle slaughterers (33.9%). Although overall positive rate of Toxoplasma antibody in slaughterers was higher, positive antibody in younger slaughterers or that of shorter duration of employment was considerably low. In addition, since positive rate of Toxoplasma antibody in swine brought to the slaughterhouse has decreased remarkably in comparison to the previous study, risk of toxoplasmosis in slaughterhouse workers also seemed to have decreased.

Abattoirs↗

PubMed1975

IgG antibody suppression of the IgM antibody response to Toxoplasma gondii in newborn rabbits.

Studies were performed in an experimental rabbit model in an attempt to explore the possibility that the absence of an IgM antibody response in human infants congenitally infected with Toxoplasma may be caused by a suppressive effect of IgG antibody passively transferred from the mother. The IgM antibody response to Toxoplasma gondii infection in newborn rabbits previously injected with IgG Toxoplasma antibody was significantly suppressed as determined by an immunofluorescent antibody assay (IgM-IFA). In newborn rabbits infected with Toxoplasma, IgM-IFA antibody was first demonstrated 15 days after infection and reached a peak titer of 1:128 in two animals on days 20 and 25. In newborn rabbits injected with IgG Toxoplasma antibody and then infected with Toxoplasma, the Igm-IFA antibody and then infected with Toxoplasma, the Igm-IFA antibody response was considerably lower; the highest titer was 1:16 and occurred 25 and 30 days after infection. The results of these studies lend support to the concept that maternally transmitted IgG may suppress the IgM antibody response in the fetus and newborn infant.

Animals↗