Altered TLR7 Expression-Mediated Immune Modulation Is Supportive of Persistent Replication and Intrauterine Transmission of HBV

Hepatitis B Virus (HBV) is posing as a serious public health threat mainly due to its asymptomatic nature of infection in pregnancy and vertical transmission. Viral sensing toll-like receptors (TLR) and Interleukins (IL) are important molecules in providing an antiviral state. The study aimed to assess the role of TLR7-mediated immune modulation, which might have an impact in the intrauterine transmission of HBV leading to mother to child transmission of the virus. We investigated the expression pattern of TLR7, IL-3, and IL-6 by RT-PCR in the placentas of HBV-infected pregnant women to see their role in the intrauterine transmission of HBV. We further validated the expression of TLR7 in placentas using Immunohistochemistry. Expression analysis by RT-PCR of TLR7 revealed significant downregulation among the Cord blood (CB) HBV DNA positive and negative cases with mean ± standard deviation (SD) of 0.43 ± 0.22 (28) and 1.14 ± 0.57 (44) with p = 0.001. IL-3 and IL-6 expression revealed significant upregulation in the CB HBV DNA-positive cases with p = 0.001. Multinomial logistic regression analysis revealed that TLR7 and IL-3 fold change and mother HBeAg status are important predictors for HBV mother to child transmission. Immunohistochemistry revealed the decreased expression of TLR7 in CB HBV DNA-positive cases. This study reveals that the downregulation of TLR7 in the placenta along with CB HBV DNA-positive status may lead to intrauterine transmission of HBV, which may lead to vertical transmission of HBV.