Toxoplasma gondii : Kinetics of Bradyzoite-Tachyzoite Interconversion in vitro

Soête, Martine; Fortier, B; Camus, Daniel; Dubremetz, Jean‐François

doi:10.1006/expr.1993.1031

Cited by 172 publications

(134 citation statements)

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“…Therefore, the finding of N. caninum tachyzoites and intermediate zoites within the same vacuole indicates that stage conversion can occur asynchronously within a cloned intravacuolar population. This is similar to findings with T. gondii (Bohne et al, 1993;Soete et al, 1993). These mixed vacuoles can rupture, as was observed in the present experiment, thereby providing an opportunity for intermediate zoites to spread to new cells.…”

Section: Discussionsupporting

confidence: 92%

Neospora Caninum in Vitro: Evidence That the Destiny of a Parasitophorous Vacuole Depends on the Phenotype of the Progenitor Zoite

Tunev

McAllister

Anderson-Sprecher

et al. 2002

Journal of Parasitology

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We previously reported that Neospora caninum can be induced to express BAG1, a bradyzoite antigen, within 3 days of culture under stress conditions. The main goals of the present experiment were to increase the expression of BAG1 in vitro (in part by extending cultures for 9 days), to observe parasitophorous vacuoles at various points of stage differentiation, and to test the ability of organisms produced in vitro to function like mature bradyzoites. Expression of BAG1 and of a tachyzoite antigen (NcSAG1) was monitored using a double-label immunofluorescence assay. For the purpose of this study, organisms expressing NcSAG1 were designated as tachyzoites, those expressing BAG1 were designated as bradyzoites, and those expressing both antigens were designated as intermediate zoites. The greatest percentage of intermediate zoites and bradyzoites (14%) occurred in bovine monocytes maintained for 9 days. These bradyzoites did not appear to be functionally mature; they did not induce patent infections in dogs, in contrast to bradyzoites that were produced in chronically infected mice. In vitro, large parasitophorous vacuoles contained either a pure population of tachyzoites or a mixture of tachyzoites and intermediate zoites, which is indicative of asynchronous stage conversion of organisms within a vacuole. Bradyzoites were first observed within small vacuoles on day 6, and bradyzoites never shared vacuoles with tachyzoites. This finding suggests that vacuoles containing bradyzoites may develop only if the cell is invaded by a zoite that has already begun bradyzoite differentiation. An alternative possibility is that cysts may develop if the establishing tachyzoite undergoes bradyzoite differentiation before multiplying. Cysts do not appear to arise from transformation of tachyzoites within large parasitophorous vacuoles.Infection with Neospora caninum, an apicomplexan protozoan, can cause abortions in cattle (Thilsted and Dubey, 1989) and goats (Barr et al., 1992). Dogs are a definitive host (McAllister et al., 1998), and ruminants are intermediate hosts. Wild canids and wild ruminants are suspected to be a natural reservoir for the infection (Dubey et al., 1999;Barling et al., 2000). NIH-PA Author Manuscript Lindsay et al., 1992) and induce patent infections in the definitive host by carnivorism.Bradyzoites are needed for scientific investigation. First, bradyzoites are needed for investigation of the factors that induce recrudescence of latent infection. Recrudescence is responsible for vertical propagation of N. caninum within infected lines of cows (Björkman et al., 1996) and may also be a cause of systemic neosporosis in dogs. Second, a supply of bradyzoites could enable the development of an oral vaccine to prevent farm dogs from shedding N. caninum oocysts and thus infecting cattle.We previously reported that N. caninum can be induced to express BAG1, a bradyzoite antigen, within 3 days of culture in human fibroblasts under stress conditions (Weiss et al., 1999). The main goals of the present experime...

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Section: Discussionsupporting

confidence: 92%

Neospora Caninum in Vitro: Evidence That the Destiny of a Parasitophorous Vacuole Depends on the Phenotype of the Progenitor Zoite

Tunev

McAllister

Anderson-Sprecher

et al. 2002

Journal of Parasitology

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“…Although the phenomenon of reactivation is far from being synchronous, as experimentally demonstrated by the simultaneous existence of all forms of T. gondii in the brain tissue [13,18], during immunosuppression in vivo the mechanisms that regulate conversion into bradyzoites are predominant and more bradyzoite surface molecules are expressed [35]. Several bradyzoite genes encoding for specific antigens have been identified and cloned including SAG4, BAG1/hsp30, LDH2 and MAG1 [7,12,20,22].…”

Section: Discussionmentioning

confidence: 99%

“…This may account for the failure of PCR which targets the B1 gene [6][7][8][9][10][11]. Recently, cloning of stage-specifically expressed genes, such as SAG1, located in the tachyzoites, or BAG1, SAG4 and MAG1, located in the bradyzoites, has enabled further analysis of regulatory mechanisms that are involved in the stage interconversion and provided insights into the pathogenesis of toxoplasmosis [3,[12][13][14][15][16][17][18].…”

Section: Introductionmentioning

confidence: 99%

The role of stage-specific oligonucleotide primers in providing effective laboratory support for the molecular diagnosis of reactivated Toxoplasma gondii encephalitis in patients with AIDS

Contini¹,

Cultrera

Seraceni³

et al. 2002

Journal of Medical Microbiology

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The switch from bradyzoites to tachyzoites is the fundamental pathogenic event that leads to Toxoplasma gondii encephalitis (TE) in patients with AIDS. Distinction between these stages is difficult, particularly when specific treatment has been started. A new approach consisting of a nested PCR (n-PCR) assay was performed on cerebrospinal fluid (CSF) specimens collected from AIDS patients with TE before or after antiparasitic therapy was initiated, to assess the efficacy of primer sets which amplify target sequences expressed on bradyzoites (SAG4 and MAG1), tachyzoites (SAG1) or both stages (B1) of T. gondii. CSF specimens were obtained from 46 patients with AIDS, of whom 27 had TE (16 first episode, 11 relapse) and 19 had other AIDS-related brain lesions (AIDS-OBL) in the absence of TE. CSF specimens from 26 HIV-negative and immunocompetent patients were also checked. All samples were tested with different primer pairs targeting the B1, SAG-1, SAG-4 and MAG-1 genes. With B1, 75% of patients with first episodes of TE were positive, compared with 36.3% of those with relapse of TE and 5.2% of those with AIDS-OLB. The SAG1 gene yielded positive values in 28.7% and 45.4% of patients with first episodes of TE or relapse of TE, respectively, and in none of the controls. With the SAG4 and MAG1 genes, 72.7% of patients with relapse of TE were detected, compared with 25% of patients with first episodes of TE and 5.2% with AIDS-OLB. None of the HIV-negative subjects showed positive PCR reactions. These results demonstrate that specific primers for the genes SAG4, MAG1 and SAG1 may be useful in AIDS patients with relapse of TE, in whom the use of PCR targeting the B1 gene may fail to detect DNA, especially when prophylaxis or treatment has been started.

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“…Despite the importance of growth mechanisms in Toxoplasma -caused disease, we know very little about the regulation of the parasite cell cycle or how growth mechanisms are linked to parasite development. It has long been established that differentiation of tachyzoites-to-bradyzoites is accompanied by a change to a slower parasite growth rate (Soete et al ., 1993;Bohne et al ., 1994) which is programmed (Jerome et al ., 1998;Radke et al ., 2003) and obligatory to development as fast growing mutant strains do not spontaneously differentiate but will do so if their growth is slowed by drug or stress treatment (Soete et al ., 1993;Bohne et al ., 1994). These and other findings (Jerome et al ., 1998) indicate that molecular switches link the growth rate and number of parasite divisions to the developmental fate of this organism, and therefore, studies of the parasite cell cycle are crucial to understand chronic as well as acute disease.…”

Section: Introductionmentioning

confidence: 99%

Genetic rescue of a Toxoplasma gondii conditional cell cycle mutant

White

Jerome

Vaishnava

et al. 2005

Molecular Microbiology

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SummaryGrowth rate is a major pathogenesis factor in the parasite Toxoplasma gondii ; however, how cell division is controlled in this protozoan is poorly understood. Herein, we show that centrosomal duplication is an indicator of S phase entry while centrosome migration marks mitotic entry. Using the pattern of centrosomal replication, we confirmed that mutant ts 11C9 undergoes a bimodal cell cycle arrest that is characterized by two subpopulations containing either single or duplicated centrosomes which correlate with the bipartite genome distribution observed at the non-permissive temperature. Genetic rescue of ts 11C9 was performed using a parental RH strain cDNA library, and the cDNA responsible for conferring temperature resistance (growth at 40 ∞ ∞ ∞ ∞ C) was recovered by recombination cloning. A single T. gondii gene encoding the protein homologue of XPMC2 was responsible for genetic rescue of the temperature-sensitive defect in ts 11C9 parasites. This protein is a known suppressor of mitotic defects, and in tachyzoites, TgXPMC2-YFP localized to the parasite nucleus and nucleolus which is consistent with the expected subcellular localization of critical mitotic factors. Altogether, these results demonstrate that ts 11C9 is a conditional mitotic mutant containing a single defect which influences two distinct control points in the T. gondii tachyzoite cell cycle.

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Toxoplasma gondii : Kinetics of Bradyzoite-Tachyzoite Interconversion in vitro

Cited by 172 publications

References 0 publications

Neospora Caninum in Vitro: Evidence That the Destiny of a Parasitophorous Vacuole Depends on the Phenotype of the Progenitor Zoite

Neospora Caninum in Vitro: Evidence That the Destiny of a Parasitophorous Vacuole Depends on the Phenotype of the Progenitor Zoite

The role of stage-specific oligonucleotide primers in providing effective laboratory support for the molecular diagnosis of reactivated Toxoplasma gondii encephalitis in patients with AIDS

Genetic rescue of a Toxoplasma gondii conditional cell cycle mutant

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