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Updated: Jun 27, 2026
Toxoplasma gondii Cyst Wall Formation in Activated Bone Marrow-derived Macrophages and Bradyzoite Conditions
Published on: August 12, 2010
[Preliminary observation on the development and dynamic changes of chronic toxoplasmosis in mice]
1College of Veterinary Medicine (Institute of Comparative Medicine), Yangzhou University, Jiangsu Co-innovation Center for Prevention and Control of Important Animal Infectious Diseases and Zoonoses, Yangzhou, Jiangsu 225009, China.
Objective:
To investigate the development and dynamic changes of cysts in the brain of mice following infection with different forms of Toxoplasma gondii, so as to provide insights into for toxoplasmosis prevention and control.
Methods:
ICR mice at ages of 6 to 8 weeks, each weighing 20 to 25 g, were intraperitoneally injected with tachyzoites of the T. gondii PRU strain at a dose of 1 × 105 tachyzoites per mouse, orally administered with cysts at a dose of 20 oocysts per mouse or oocysts at a dose of 200 oocysts per mouse for modeling chronic T. gondii infection in mice, and the clinical symptoms and survival of mice were observed post-infection. Mice were orally infected with T. gondii cysts at doses of 10 (low-dose group), 20 (medium-dose group), 40 cysts per mouse (high-dose group), and the effect of different doses of T. gondii infections on the number of cysts was examined in the mouse brain. Mice were orally administered with T. gondii cysts at a dose of 20 cysts per mouse, and grouped according to gender (female and male) and time points of infections (20, 30, 60, 90, 120, 150, 180 days post-infection), and the effects of gender and time points of infections on the number of cysts was examined in the mouse brain. In addition, mice were divided into the tachyzoite group (Group T), the first-generation cyst group (Group C1), the second-generation cyst group (Group C2), the third-generation cyst (Group C3) and the fourth-generation cyst group (Group C4). Mice in the Group T were intraperitoneally injected with T. gondii tachyzoites at a dose of 1 × 105 tachyzoites per mouse, and the cysts were collected from the mouse brain tissues 30 days post-infection, while mice in the Group C1 were orally infected with the collected cysts at a dose of 30 cysts per mouse. Continuous passage was performed by oral administration with cysts produced by the previous generation in mice, and the effect of continuous passage on the number of cysts was examined in the mouse brain.
Results:
Following infection with T. gondii tachyzoites, cysts and oocysts in mice, obvious clinical symptoms were observed on days 6 to 13 and mice frequently died on days 7 to 12. The survival rates of mice were 67.0%, 87.0% and 53.0%, and the mean numbers of cysts were (516.0 ± 257.2), (1 203.0 ± 502.0) and (581.0 ± 183.1) in the mouse brain (F = 11.94, P < 0.01) on day 30 post-infection with T. gondii tachyzoites, cysts and oocysts, respectively, and the numbers of cysts in the brain tissues were significantly lower in mice infected with T. gondii tachyzoites and oocysts than in those infected with cysts (all P values < 0.01). The survival rates of mice were 87.0%, 87.0% and 60.0%, and the mean numbers of cysts were (953.0 ± 355.5), (1 084.0 ± 474.3) and (1 113.0 ± 546.0) in the mouse brain in the low-, medium- and high-dose groups on day 30 post-infection, respectively (F = 0.42, P > 0.05). The survival rates of male and female mice were 73.0% and 80.0%, and the mean numbers of cysts were (946.4 ± 411.4) and (932.1 ± 322.4) in the brain tissues of male and female mice, respectively (F = 1.63, P > 0.05). Following continuous passage, the mean numbers of cysts were (516.0 ± 257.2), (1 203.0 ± 502.0), (896.8 ± 332.3), (782.5 ± 423.9) and (829.2 ± 306.0) in the brain tissues of mice in the T, C1, C2, C3 and C4 groups, respectively (F = 4.82, P < 0.01), and the number of cysts was higher in the mouse brain in Group 1 than in Group T (P < 0.01). Following oral administration of 20 T. gondii cysts in mice, cysts were found in the moues brain for the first time on day 20 post-infection, and the number of cysts gradually increased over time, peaked on days 30 and 90 post-infection and then gradually decreased; however, the cysts were still found in the mouse brain on day 180 post-infection.
Conclusions:
There is a higher possibility of developing chronic T. gondii infection in mice following infection with cysts than with oocysts or tachyzoites and the most severe chronic infection is seen following infection with cysts. The number of cysts does not correlate with the severity of chronic T. gondii infection, and the number of cysts peaks in the mouse brain on days 30 and 90 post-infection.
Insights
Mice infected with Toxoplasma gondii cysts develop more severe chronic infections. The number of cysts in the brain peaks at 30 and 90 days post-infection, not correlating with infection severity.
Area of Science:
- Parasitology
- Immunology
- Neuroscience
Background:
- Toxoplasma gondii (T. gondii) is a protozoan parasite causing toxoplasmosis.
- Chronic T. gondii infection establishes persistent cysts in the brain.
- Understanding cyst dynamics is crucial for disease management.
Purpose of the Study:
- To investigate the development and dynamic changes of T. gondii brain cysts in mice.
- To compare cyst formation following infection with different T. gondii forms (tachyzoites, cysts, oocysts).
- To provide insights for toxoplasmosis prevention and control.
Main Methods:
- Mice were infected with T. gondii tachyzoites, cysts, or oocysts via intraperitoneal injection or oral administration.
- Dose-response and time-course studies were conducted to assess cyst burden.
- Continuous passage experiments were performed to evaluate cyst generation effects.
- Brain cyst numbers were quantified at various time points post-infection.
Main Results:
- Infection with T. gondii cysts led to higher cyst burdens in mouse brains compared to tachyzoites or oocysts.
- Clinical symptoms were observed between days 6-13, with mortality peaking days 7-12.
- Brain cyst numbers peaked at 30 and 90 days post-infection, remaining detectable for up to 180 days.
- No significant correlation was found between cyst number and chronic infection severity.
Conclusions:
- Infection with T. gondii cysts poses a higher risk for severe chronic infection in mice.
- The number of brain cysts does not directly correlate with the severity of chronic toxoplasmosis.
- Brain cyst dynamics show a peak at 30 and 90 days, highlighting critical time points in infection.
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