Gut commensal bacteria exacerbate toxoplasmosis associated with TgSheepCHn5 (ToxoDB#2) and TgRedpandaCHn1 (ToxoDB#20) through Th1 immune response.

Oral infection of mice with several strains of Toxoplasma gondii results in intestinal pathological lesions, which contributes to the invasion of this parasite. However, the exact mechanism is unclear, and only a few strains have been explored. Here, T. gondii TgSheepCHn5 and TgRedpandaCHn1 strains from sheep and red panda were evaluated. The TgSheepCHn5 and TgRedpandaCHn1 strains induced intestinal lesions, loss of Paneth cells, and gut commensal bacteria dysbiosis in Swiss Webster mice. The lesions and loss of Paneth cells were dependent on IFN-γ and gut commensal bacteria during T. gondii infection. Deleting IFN-γ or gut commensal bacteria suppressed the Th1 immune response, alleviated the lesions and parasite loading, and upregulated the number of Paneth cells. Loss of IFN-γ production accelerated mice death, whereas the deletion of gut commensal bacteria enhanced the survival time of the host. The Th1 cell immune responses have positive and negative effects on toxoplasmosis, resistance to T. gondii infection, and acceleration intestine lesions. Adjustment of Th1 cell responses and gut commensal bacteria may be effective treatments for toxoplasmosis.