CXCR3-Dependent Immune Pathology in Mice following Infection with Toxoplasma gondii during Early Pregnancy

Abstract

Toxoplasmosis is a worldwide zoonosis caused by the obligate intracellular parasite Toxoplasma gondii. The symptoms of congenital toxoplasmosis range from embryonic death and resorption to subclinical infection, but the mechanism of disease onset remains unclear. C-X-C motif chemokine receptor 3 (CXCR3) is highly expressed in Th1-associated immune cells and plays an important role in the trafficking and activation of immune cells. However, the roles of CXCR3 in T. gondii-induced fetal loss and the molecular mechanism of embryo resorption remain poorly understood. In this study, we investigated the role of CXCR3 in fetal wastage caused by T. gondii infection using CXCR3-deficient (CXCR3-/-) mice. CXCR3-/- and wild-type pregnant mice were inoculated intraperitoneally with T. gondii tachyzoites on day 3.5 of gestation (Gd3.5). Pregnancy rates decreased as the pregnancy progressed in both infected groups; however, infected CXCR3-/- mice showed a significant fetal loss at Gd13.5 compared with that at Gd7.5. All embryos of the infected groups showed necrosis, and embryo resorption was significantly increased in infected CXCR3-/- compared with wild-type mice at Gd13.5. The parasite load of fetoplacental tissues was significantly increased in CXCR3-/- mice at Gd10.5. Moreover, mRNA expression levels of inducible nitric oxide synthase were significantly increased in fetoplacental tissues from infected wild-type mice compared to infected CXCR3-/- mice following the infection. These results suggested that CXCR3-dependent immune responses provide anti- Toxoplasma activity and play an essential role in reducing embryo resorption and fetal loss caused by T. gondii infection during early pregnancy.