Pathobiology of human RH strain induced experimental toxoplasmosis in murine model

Humane Endpoints in Swiss Webster Mice Infected with Toxoplasma gondii RH Strain

The highly virulent Toxoplasma gondii RH strain is maintained through successive passages in mice, but there is still a lack of studies that refine these procedures from a 3Rs perspective, where humanitarian ideals aim to minimize the stress, pain, or suffering of the animals used in the research without the loss of results. The aim of this study was to establish humane endpoints in Swiss Webster mice inoculated with the T. gondii RH strain. A total of 52 mice were infected with 5 × 106 tachyzoites/mL and monitored for periods of up to 5 days. The parameters body weight; hair condition; higher than normal body temperature; hypothermia; respiratory function; pain; soft stools or diarrhea; bloody diarrhea; tense, nervous, or in distress during handling; and ascites were recorded daily in score tables. The results showed that prominent piloerection, respiratory function, pain parameters, and ascites are important clinical signs to be used as a cut-off point for implementing euthanasia. The application of this refinement method helped to avoid animal suffering and pain without compromising the number of parasites recovered. We therefore suggest adopting these parameters in research protocols that require the maintenance of the T. gondii RH strain in murine models to avoid and reduce animal suffering.

Immunobiotic and Paraprobiotic Potential Effect of Lactobacillus casei in a Systemic Toxoplasmosis Murine Model

One of the main characteristics of probiotics is their ability to stimulate and modulate the immune response regardless of their viability. Lactobacillus casei (Lc) can stimulate local and systemic immunity, in addition to the activation of macrophages at sites distant from the intestine. Activated macrophages limit the replication of intracellular protozoa, such as Toxoplasma gondii, through the production of nitric oxide. The present study aimed to evaluate the protection generated by treatment with viable and non-viable Lc in the murine systemic toxoplasmosis model. CD1 male mice were treated with viable Lc (immunobiotic) and non-viable Lc (paraprobiotic), infected with tachyzoites of Toxoplasma gondii RH strain. The reduction of the parasitic load, activation of peritoneal macrophages, inflammatory cytokines, and cell populations was evaluated at 7 days post-infection, in addition to the survival. The immunobiotic and paraprobiotic reduced the parasitic load, but only the immunobiotic increased the activation of peritoneal macrophages, and the production of interferon-gamma (IFN-γ), tumor necrosis factor (TNF), and interleukin-6 (IL-6) while the paraprobiotic increased the production of monocyte chemoattractant protein-1 (MCP-1) and T CD4⁺CD44⁺ lymphocytes. Viable and non-viable Lc increases survival but does not prevent the death of animals. The results provide evidence about the remote immunological stimulation of viable and non-viable Lc in an in vivo parasitic model.

Ginsenoside Rh2 attenuates microglial activation against toxoplasmic encephalitis via TLR4/NF-κB signaling pathway

Background

Ginsenoside Rh2 (GRh2) is a characterized component in red ginseng widely used in Korea and China. GRh2 exhibits a wide range of pharmacological activities, such as anti-inflammatory, antioxidant, and anticancer properties. However, its effects on Toxoplasma gondii (T. gondii) infection have not been clarified yet.

Methods

The effect of GRh2 against T. gondii was assessed under in vitro and in vivo experiments. The BV2 cells were infected with tachyzoites of T. gondii RH strain, and the effects of GRh2 were evaluated by MTT assay, morphological observations, immunofluorescence staining, a trypan blue exclusion assay, reverse transcription PCR, and Western blot analyses. The in vivo experiment was conducted with BALB/c mice inoculated with lethal amounts of tachyzoites with or without GRh2 treatment.

Results and conclusion

The GRh2 treatment significantly inhibited the proliferation of T. gondii under in vitro and in vivo studies. Furthermore, GRh2 blocked the activation of microglia and specifically decreased the release of inflammatory mediators in response to T. gondii infection through TLR4/NF-κB signaling pathway. In mice, GRh2 conferred modest protection from a lethal dose of T. gondii. After the treatment, the proliferation of tachyzoites in the peritoneal cavity of infected mice markedly decreased. Moreover, GRh2 also significantly decreased the T. gondii burden in mouse brain tissues. These findings indicate that GRh2 exhibits an anti–T. gondii effect and inhibits the microglial activation through TLR4/NF-κB signaling pathway, providing the basic pharmacological basis for the development of new drugs to treat toxoplasmic encephalitis.

Development of a murine vertical transmission model for Toxoplasma gondii oocyst infection and studies on the efficacy of bumped kinase inhibitor (BKI)-1294 and the naphthoquinone buparvaquone against congenital toxoplasmosis

Objectives

Establishment of a mouse model for congenital toxoplasmosis based on oral infection with oocysts from Toxoplasma gondii ME49 and its application for investigating chemotherapeutic options against congenital toxoplasmosis.

Methods

CD1 mice were mated, orally infected with 5, 25, 100, 500 or 2000 oocysts and monitored for clinical signs and survival of dams and pups until 4 weeks post partum . The parasite burden in infected mice was quantified by real-time PCR in lungs, brains and, in the case of surviving pups, also in eyes. Seroconversion was assessed by ELISA. T. gondii cysts in brain were identified by immunofluorescence. In a second experiment, pregnant CD1 mice challenged with 20 oocysts/mouse were treated with buparvaquone or the calcium-dependent protein kinase 1 inhibitor bumped kinase inhibitor (BKI)-1294 and the outcome of infection was analysed.

Results

T. gondii DNA was detected in the brain of all infected animals, irrespective of the infection dose. Seroconversion occurred at 3 weeks post-infection. Most pups born to infected dams died within 1 week post partum , but a small fraction survived until the end of the experiment. T. gondii DNA was detected in the brain of all survivors and half of them exhibited ocular infection. Chemotherapy with both compounds led to dramatically increased numbers of surviving pups and reduced cerebral infection. Most efficient were treatments with BKI-1294, with 100% survivors and only 7% brain-positive pups.

Conclusions

BKI-1294 and buparvaquone exert excellent activities against transplacental transmission in pregnant mice.