Immune-enhancing activity of Astragalus maximus extract for inhibiting the Toxoplasma gondii infection: experimental research

BACKGROUND: This study aimed to evaluate the in-vitro anti-Toxoplasma effects and cytotoxicity effects of Astragalus maximus chloroformic extract (AMCE) on the T. gondii Rh strain. METHODS: In-vitro effects of AMCE (2–64 µg/ml) on tachyzoites were measured by MTT assay for 48 h. The effects of AMCE on infectivity rate and intracellular parasites into macrophage cells (J774-A1) were evaluated. The Griess reaction assay and quantitative real-time PCR were used to determine the nitric oxide (NO) and the mRNA expression levels of IFN-γ and iNOS in infected J774-A1 macrophage cells. RESULTS: The mortality rate of the parasites significantly (P<0.001) increased in a dose-dependent manner with an IC(50) value of 9.85 μg/ml. The rate of infection and the mean number of intracellular tachyzoites in macrophage cells were significantly reduced (P<0.001) after exposure of the macrophage cells to AMCE. The mRNA expression levels of IFN-γ, iNOS, and NO production in macrophage cells after treatment with the AMCE were increased, especially at the concentration of ½ IC(50) and IC(50) (P<0.001). CONCLUSION: The findings of the current in vitro investigation revealed favorable anti-Toxoplasma effects of AMCE against tachyzoites and intracellular forms of T. gondii. Despite the fact that the accurate anti-Toxoplasma mechanisms of AMCE are not clear, our results showed that triggering NO production and cellular immunity can be considered as the main mechanisms of action of AMCE for controlling and eliminating T. gondii. However, further surveys are mandatory to assess the efficacy and safety of AMCE in an animal model and its accurate mechanisms of action.