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PubMed1981

Experimental infection of the guinea pig inner ear with Toxoplasma gondii.

Based on the question whether toxoplasma gondii is a potential pathogenetic factor in sudden deafness and vertigo (especially in the acquired form of Toxoplasmosis) we started a series of investigations, dealing with direct, local, hematogenous, and intracisternal infection of the guinea pig cochlea with toxoplasma gondii. Three of ten directly inoculated and one of five hematogenously infected guinea pigs showed a severe labyrinthitis in electron and light microscopy. Thus, we could demonstrate that toxoplasma gondii is a potent pathogenetic factor in acute inner ear disturbances in laboratory animals. Toxoplasmosis should always be considered in cases with sudden deafness and vertigo without obvious other cause. With a specific therapy the labyrinthine disturbances can apparently be successfully treated.

Animals↗

PubMed1995

Limited value of cerebrospinal fluid for direct detection of Toxoplasma gondii in toxoplasmic encephalitis associated with AIDS.

The diagnosis of acquired immunodeficiency syndrome-associated toxoplasmic encephalitis (TE), a typically focal disease resulting from reactivation of tissue cysts, relies mainly on indirect diagnostic methods. In a prospective study, we investigated the value of detection of Toxoplasma gondii in cerebrospinal fluid (CSF) by using the polymerase chain reaction and the mouse inoculation test. Twenty-four patients with 26 episodes of TE, 2 HIV-infected patients with primary acute Toxoplasma infection, and 38 HIV-infected control patients with latent Toxoplasma infection were investigated. Detection of T. gondii in CSF by both methods was possible in only 3 of the TE patients (11.5%), the remaining patients being negative with either of the methods. In contrast, T. gondii DNA was detected in both of the acutely infected patients, indicating that in primary acute toxoplasmosis parasites may easily be found in the CSF, whereas in the majority of TE cases in immunocompromised patients, T. gondii parasites do not gain access to the CSF drawn by lumbar puncture.

AIDS-Related Opportunistic Infections↗

PubMed1984

Topographical localization of distinct antigenic domains of Toxoplasma gondii with the aid of monoclonal antibodies.

In the present study, a panel of six individual hybridoma derived antibodies produced against the BK strain of Toxoplasma gondii were evaluated for their reactivity in an immunofluorescence test. Each of the six monoclonal antibodies demonstrated a unique pattern of fluorescence localized to distinctive regions on the toxoplasmas. Although all of the six detected antigenic determinants which were shared by at least four different T. gondii strains, monoclonal antibody TG-E4A17 has disclosed hitherto unrecognized population differences among the BK or PH strain parasites. The fact that some of the antigenic molecules are restricted to distinct regions of the toxoplasmas may have implications in the infections process/immune response.

Animals↗

PubMed1979

[Modes of entry of Toxoplasma gondii trophozoites into normal mouse peritoneal macrophage and HeLa cell monolayers. A phase-contrast microcinematographic study (author's transl)].

The mode of entry of living trophozoites of Toxoplasma gondii (RH strain) into normal mouse peritoneal macrophage and HeLa cell monolayers was studied by phase-contrast microcinematography. The results have shown that Toxoplasma can enter into macrophages either by phagocytosis (Figs. 1 and 2) and/or by active penetration (Fig. 3). Only the latter process was observed with normally non-phagocytic HeLa cells (Fig. 4). During this process the parasites actively moved towards the host-cells by flexion and penetrated them always through their sharpest end. Active penetration was a rapid phenomenon (about 20 s at 37 degrees C) and was accompanied by a series of morphological changes, i.e., elongation of the anterior end, contraction and swelling of the parasite body. Contrasting with phagocytosis, toxoplasmas which had penetrated into the cell were not immediately isolated from the host-cytoplasm by a microscopically discernable vacuole. The nature of the process of penetration (pressure and/or perforation of the plasma membrane) is discussed.

Animals↗

PubMed1978

[Comparative review of the developmental biology of the genera Sarcocystis, Frenkelia, Isospora, Cystoisospora, Hammondia, Toxoplasma and Besnoitia (author's transl)].

A review is given of the advances in our knowledge of the developmental biology of the so-called cyst-forming coccidia in the years from 1974 to 1978. Until 1970 only 6 Isospora species were known to occur in cats, dogs and men. After the discovery of the coccidian nature of the genera Toxoplasma, Sarcocystis, Besnoitia and Frenkelia, and after the discovery of the new genus Hammondia the number of known species rose to over 30. In addition it could be shown that also birds of prey, owls and reptiles serve as final hosts for several Sarcocystis and Frenkelia species. The coccidia with isosporoid oocysts can be classified into two major groups: Species with gamogony and sporogony in the final host (Sarcocystis, Frenkelia) and species with schizogony and gamogony in the final host and sporogony on the ground (Isospora, Cystoisospora, Hammondia, Toxoplasma, Besnoitia). The subdivision of the first group into the genera Sarcocystis and Frenkelia based on the localization of their cysts in the musculature and in the brain, respectively, cannot be upheld in the future. Their classification into organisms with small cystozoites of about 7 microm with birds or reptiles as final hosts (Sarcocystis and Frenkelia species of rodents) and those with large cystozoites of about 15 microm and mammals as final hosts (Sarcocystis spp. of domestic animals and rodents) would be more significative. The second group can be subdivided into monoxenous species (Isospora), species with an optional intermediate host in which no or only slight multiplication occurs (Cystoisospora) and in genera with a multiplication in two phases in the intermediate host (Hammondia, Toxoplasma, Besnoitia). The nomenclature of single species is very controversial. As an example the controversial apprehension of the taxonomy of the Sarcocystis species of cattle is discussed. An application has been submitted to the International Commission for the Zoological Nomenclature to delcare a number of names as nomina dubia and to introduce unambiguous names for those organisms for which type specimens are available.

Animals↗

PubMed1979

[Fine-structure changes in Toxoplasma gondii trophozoites after deep-freezing with dimethyl sulphoxide (author's transl)].

The changes observed in trophozoites of Toxoplasma gondii after deep-freeze preservation were examined by electron microscopy. Toxoplasmas (strain BK) from peritoneal exudate of infected NMRI mice were supended in Ringer's solution, deep-frozen in liquid nitrogen with 5% dimethylsulphoxide (DMSO), and compared after thawing with control samples with and without the addition of DMSO. Slight structural changes such as widening of endoplasmic reticulum, formation of fissures in the cytoplasm, and loosening of chromatin were only observed in some of the free toxoplasmas of the DMSO control. Among the deep-frozen parasites, about 1/5 of the free stages showed no or only slight morphological changes. In contrast to this, almost all intracellular forms found in macrophages showed lesions. The most remarkable change was a partial destruction of the inner cell membrane complex. The outflow of ribosome-containing protoplasm with ballon-like swelling of the outer elementary membrane was observed as a consequence of this frequent lesion. The outflow of protoplasm induced a drastic decrease in the electronic density of the whole cytoplasm. Other characteristic degenerative signs were vacuolation of cytoplasm up to formation of great optically empty spaces, widening of the perinuclear space, swelling of mitochondria, disintegration of rhoptria, micronemata, and Golgi zone, coarse-plaque loosening, and displacement of electron-dense areas of the nucleus up to disintegration with maintenance of the karyoplasm. In some almost completely disintegrated trophozoites, enlarged mitochondria with remarkable electronic density were observed. Apart from the cell membrane, the conoid was the longest-persisting organelle. The alterations observed after deep-freezing permit the conclusion that the free cells, which were only slightly impaired or not at all, remained infective.

Animals↗

PubMed1992

Toxoplasma gondii: differentiation and death of bradyzoites.

The living parasites in Toxoplasma cysts cannot be eradicated by current therapy and maintain latent infections for many years. Relatively little is known about encysted Toxoplasma. We therefore undertook studies using mice infected with the avirulent ME 49 strain of Toxoplasma. The bradyzoites in young (12- to 17-day-old) cysts contained the same organelles as did tachyzoites. The bradyzoites of older cysts (4 weeks postinoculation) had differentiated, losing certain organelles and acquiring others. Our major new finding was that in animals inoculated greater than or equal to 4 weeks previously, some bradyzoites were totally disrupted, spilling their contents (perhaps including lytic substances) into the cyst matrix. Many older bradyzoites in the same cysts lacked internal membranes and their viability was questionable, but there were also occasional parasites resembling viable tachyzoites and mature bradyzoites, organisms that might possibly initiate daughter cyst formation after cyst rupture. The life span of an individual bradyzoite may be shorter than formerly appreciated despite the prolonged course of latent infections.

Animals↗

PubMed1998

Estimation of the avidity of immunoglobulin G for routine diagnosis of chronic Toxoplasma gondii infection in pregnant women.

Present serological methods differentiate poorly between acute and chronic toxoplasmosis in pregnant women, particularly when immunoglobulin G (IgG) and immunoglobulin M (IgM) antibodies to Toxoplasma gondii are present simultaneously. In the present study, a simple test for discriminating between high-avidity antibodies, which are usually present in chronic infections, and low-avidity antibodies, typical of acute infection, was evaluated. Sera were evaluated for Toxoplasma gondii antibodies using a commercial enzyme immunoassay, but a duplicate well was washed in 6M urea to disrupt low-avidity complexes. Results are expressed as the percentage of antibodies resisting elution by urea. Equivocal sera (n = 493) containing both IgG and IgM Toxoplasma gondii antibodies from 309 pregnant women whose status as chronically or acutely infected had been independently determined using standard methods were evaluated for antibody avidity. A value of > 35% elution-resistant antibodies was always associated with chronic infection and could absolutely exclude a recent (< 3 months) infectious incident. Values of < 35% require repeat testing four weeks later to confirm the patient's status, since a proportion of individuals with chronic toxoplasmosis maintain low-avidity antibodies over long periods. This inexpensive, simple method can provide reassurance to clearly chronically infected individuals and avoids the need for repeated testing in these cases.

Acute Disease↗

PubMed1996

Performance of European laboratories testing serum samples for Toxoplasma gondii.

One hundred twenty-nine European laboratories participated in a collaborative, multicentre study designed to evaluate the overall reliability of different serological techniques for diagnosis of Toxoplasma gondii infection. Five freeze-dried reference sera were distributed to each laboratory, each of which analysed the sera with its routine methods. The enzyme-linked immunosorbent assay was the technique used most frequently, followed by the immunofluorescent antibody technique. Only nine laboratories performed the Sabin-Feldman dye test. In general, there was good concordance between qualitative results, but for sera with low concentrations of Toxoplasma gondii-specific IgG antibodies, some false-negative results were found. For specific IgM and IgA antibodies, the immunosorbent agglutination assay proved the most sensitive. The present study demonstrates the need for regular assessment of laboratory serodiagnosis of Toxoplasma gondii infection.

Animals↗

PubMed1979

Investigation into the occurrence of toxoplasma in pharyngeal and palatine tonsils by inoculation of tonsillar tissues into mice.

Among randomly chosen persons in the age group one to seven years the generally accepted proportion of positive dye tests for Toxoplasma is about eight per cent. The 124 children in this age group studied by us represent a selected group in which a higher percentage is to be expected. The group included 63 boys and 61 girls, from whom no blood samples were available for serological investigation. An arbitrary percentage of twice the eight per cent would result in 20 cases with a positive dye test. In the four successful attempts to isolate Toxoplasma all four cases were boys. Among 20 persons aged 14 to 21 years in whom a positive dye test could actually be established, one attempt to isolate the organism in a girl of 16 years of age was successful. No generalized lymph node enlargements were mentioned in the history of the five successful cases, only relapsing laryngo-pharyngeal symptoms. In the five successful isolations the Toxoplasma organisms present in the tonsillar organs appeared not to be virulent for the mice used; the organism was recovered in the cystic form from the brains of the mice. In subsequent animal passages the virulence could be influenced by the number of cysts per inoculum.

Adolescent↗

PubMed1995

Multicenter evaluation of a new commercial assay for detection of immunoglobulin M antibodies to Toxoplasma gondii. Multicenter Study Group.

A new commercial assay for detection of IgM-specific antibodies to Toxoplasma gondii (IMx Toxo IgM, Abbott, USA), based on microparticle enzyme immunoassay technology, was evaluated at 15 clinical sites in Europe and the USA. Performance characteristics were established by testing clinical specimens collected randomly from pregnant women, blood donors, individuals with suspected Toxoplasma gondii infection and individuals confirmed HIV positive. Reference testing was performed using Toxo-M EIA (Abbott). Specimens evaluated at European sites yielding discordant results between the new assay and the reference EIA were further tested with an immunosorbent agglutination assay; at sites in the USA, discordant results were resolved using Platelia Toxo IgM (Sanofi, France) and Vidas Toxo IgM (bioMérieux, France) assays. In addition, matched plasma and serum, heat-treated and non-heat-treated specimens, and fresh and frozen specimens were evaluated at the USA sites. At European sites the new commercial assay had a sensitivity of 95.6% (196/205), a specificity of 99.8% (3,137/3,143) and an agreement of 99.6% (3,333/3,348) following resolution of discordant results; sensitivity in the USA was 97.4% (184/189), specificity was 99.8% (1,204/1,207) and agreement was 99.4% (1,388/1,396) following resolution. The new IMx Toxo IgM is a sensitive and specific assay for measurement of IgM antibodies to Toxoplasma gondii in human serum and plasma.

Animals↗

PubMed1996

High predictive value of Toxoplasma gondii IgG antibody levels in HIV-infected patients for diagnosis of cerebral toxoplasmosis.

The results of serological tests for Toxoplasma gondii IgG in 31 HIV-infected patients with toxoplasmic encephalitis (TE) and 49 HIV-infected patients seropositive for Toxoplasma gondii but without TE were compared. All patient had a CD4+ lymphocyte count < 150/microliters. Of the TE patients, 22 (71%) were designated as having relatively high IgG levels on the basis of the following Toxoplasma IgG titre combination: Sabin-Feldman test > or = 1:256, indirect hemagglutination test > or =1:1024, direct agglutination test > or = 1:14,580. Only 3 patients without TE had relatively high IgG titres. Relatively high IgG titres indicated TE with a positive predictive value of 88% in HIV-infected patients with CD4+ cell counts < 150/microliters, and could be observed in most patients several months prior to the first clinical and radiological signs of TE.

AIDS-Related Opportunistic Infections↗

PubMed1996

Interlaboratory comparison of polymerase chain reaction for the detection of Toxoplasma gondii DNA added to samples of amniotic fluid.

To investigate the accuracy of the polymerase chain reaction (PCR) method for the detection of Toxoplasma gondii in clinical specimens, aliquots of amniotic fluid to which known amounts of Toxoplasma gondii DNA had been added were tested by five European Centres. Four laboratories were able to detect DNA at levels equivalent to ten tachyzoites or less, including two that detected DNA equivalent to a single parasite. Two laboratories erroneously found one of eight negative control samples to be positive. These findings confirm that the high level of sensitivity associated with the PCR method can be readily achieved under routine laboratory conditions, but they also underscore the potential for both false-positive and false-negative findings to occur. Furthermore, the results confirm the urgent need for an external quality assurance scheme to support laboratories employing PCR in a clinical context for the detection of Toxoplasma gondii.

Amniotic Fluid↗

PubMed1995

Prevalence of anti-Toxoplasma gondii antibodies in the population of the area of Parma (Italy).

Between 1987 and 1991, the prevalence of IgG antibodies to Toxoplasma gondii was determined by ELISA in 28,247 serum samples belonging to 19,432 subjects of the area of Parma (Italy). The overall prevalence was 48.5%. The correlation of infection with age, performed on 420 sera, showed a significant increase of positivity until 30-40 approximately years. In consecutive sera obtained from 172 subjects, the IgG and IgM production was analyzed for about 8 months, and four different patterns were delineated which were comprehensive of the wide range of immunological responses to Toxoplasma gondii exposure observed. Among pregnant females the prevalence of anti-Toxoplasma gondii antibodies was 48.7%, and 5 cases of seroconversion during the pregnancy were observed (0.27%) from which two cases of congenital toxoplasmosis originated.

Animals↗

PubMed1995

Seroepidemiology of Toxoplasma gondii among pregnant women in different parts of Sweden.

Surveys of pregnant women in four areas of Sweden in 1987-88, reveal a significant trend for decrease in Toxoplasma seroprevalence from Gotland island (26%, n = 467) in the south through Orebro county (18%, n = 1413) and Stockholm area (18%, n = 939), to Northern Sweden (12%, n = 837). No within area differences were observed between samples from rural and urban localities. Quantitative antibody data indicate marginally higher levels in the north than in the south, and a significant declining trend by age only in Orebro county. Incidence models are used to describe age-seroprevalence profiles for each area, using different assumptions about age- and time-specific infection rates, and to estimate the risk of maternal infection at the time of the survey. It is shown that the patterns of seroprevalence with age in Orebro county and Northern Sweden, but not Gotland island or Stockholm, strongly implicate time-dependent changes in Toxoplasma incidence, consistent with a declining incidence in the past which has possibly been reversed in recent years. The estimates of Toxoplasma incidence and risk of maternal toxoplasmosis are strongly dependent upon the underlying assumption of temporal change in incidence, with wide ranges in the predicted values. These studies demonstrate the difficulties in interpretation of horizontal cross-sectional data and the need for longitudinal studies of age-prevalence and seroconversion in the determination of the true risk of maternal toxoplasmosis.

Adolescent↗

PubMed1991

In vivo activity of the macrolide antibiotics azithromycin, roxithromycin and spiramycin against Toxoplasma gondii.

The macrolide antibiotics azithromycin, roxithromycin and spiramycin were examined in parallel for in vivo activity against Toxoplasma gondii. Azithromycin was considerably more active in protecting mice against death due to acute toxoplasmosis even when the other two antibiotics were used at twice its dose. The higher activity of azithromycin prompted a further examination of its activity against five different strains of Toxoplasma gondii, including two isolated from patients with AIDS. Although variable degrees of protection against death were noted, treatment with 200 mg/kg/day for ten days was sufficient to promote survival of 100% of mice infected with inocula as high as 1 x 10(5) tachyzoites of Toxoplasma gondii. 90% of mice inoculated with 1 x 10(5) tachyzoites of strain MO, isolated from an AIDS patient, and treated orally with 200 mg/kg/day for ten days survived the infection whereas only 40% of mice infected with the same inoculum of the SOU strain, also isolated from an AIDS patient, survived. Tissue concentrations of azithromycin were examined in treated infected and non-infected mice. In both groups of mice azithromycin attained high concentrations in liver, spleen and heart, which exceeded concurrent serum levels by 25- to 200-fold. The concentrations in the brain were almost tenfold higher than the concentrations in serum after treatment with 200 mg/kg/day for ten days. Moreover, the concentrations in brains of infected mice were approximately two-fold higher than in brains of non-infected mice.

Animals↗

PubMed1991

Role of gamma interferon in Toxoplasma gondii infection.

Toxoplasma gondii has emerged as an important pathogen in the ever increasing numbers of patients with disorders of the immune system. Better understanding of the mechanisms of resistance of the host against this protozoan is important for development of safe, effective alternative treatment regimens for toxoplasmosis. Gamma interferon is the cytokine that plays a central role in protection against Toxoplasma gondii. The purpose of this review is to highlight the current knowledge of the role of gamma interferon in Toxoplasma gondii infection.

Acquired Immunodeficiency Syndrome↗

PubMed1990

Evaluation of immunoblotting for the detection of Toxoplasma gondii immunoglobulin M antibodies.

Immunoblot analysis was used to detect human IgM antibodies to Toxoplasma gondii in 20 patients with recent toxoplasmosis, 30 immune individuals, 30 non-immune individuals, and 24 children less then two years old. Analysis of the IgM strips revealed that specific IgM antibodies detectable after a recent Toxoplasma gondii infection react with the same antigens as the 'natural' antibodies present in the sera of immune and non-immune individuals and in the sera of young children. These data indicate that immunoblotting is not useful as a reference method for Toxoplasma gondii IgM detection, and suggest that improvement of the specificity of IgM detection will remain difficult.

Animals↗