Maternal Murine Cytomegalovirus Infection during Pregnancy Up-regulates the Gene Expression of Toll-like Receptor 2 and 4 in Placenta

Increasing evidence has revealed that maternal cytomegalovirus (CMV) infection may be associated with neurodevelopmental disorders in offspring. Potential relevance between the placental inflammation and CMV-related autism has been reported by clinical observation. Meanwhile, abnormal expression of Toll-like receptor 2 (TLR2) and TLR4 in placenta of patients with chorioamnionitis was observed in multiple studies. IL-6 and IL-10 are two important maternal inflammatory mediators involved in neurodevelopmental disorders. To investigate whether murine CMV (MCMV) infection causes alterations in placental IL-6/10 and TLR2/4 levels, we analyzed the dynamic changes in gene expression of TLR2/4 and IL-6/10 in placentas following acute MCMV infection. Mouse model of acute MCMV infection during pregnancy was created, and pre-pregnant MCMV infected, lipopolysaccharide (LPS)-treated and uninfected mice were used as controls. At E13.5, E14.5 and E18.5, placentas and fetal brains were harvested and mRNA expression levels of placental TLR2/4 and IL-6/10 were analyzed. The results showed that after acute MCMV infection, the expression levels of placental TLR2/4 and IL-6 were elevated at E13.5, accompanied by obvious placental inflammation and reduction of placenta and fetal brain weights. However, LPS 50 μg/kg could decrease the EL-6 expression at E13.5 and E14.5. This suggests that acute MCMV infection during pregnancy could up-regulate the gene expression of TLR2/4 in placental trophoblasts and activate them to produce more proinflammatory cytokine IL-6. High dose of LPS stimulation (50 μg/kg) during pregnancy can lead to down-regulation of IL-6 levels in the late stage. Imbalance of IL-6 expression in placenta might be associated with the neurodevelopmental disorders in progeny.