In contrast to horizontal transmission of hepatitis B virus (HBV) between adults, which often leads to self-limited acute infection, vertical transmission of HBV from mother to child often leads to chronic infection. However, the mechanisms linking vertical transmission with chronic infection are not known. We developed a mouse model to study the effect of maternal HBV infection on HBV persistence in offspring and found that HBV carried by the mother impaired CD8+ T cell responses to HBV in her offspring, resulting in HBV persistence. This impairment of CD8+ T cell responses was mediated by hepatic macrophages, which were predisposed by maternal HBV e antigen (HBeAg) to support HBV persistence by upregulation of inhibitory ligand PD-L1 and altered polarization upon restimulation with HBeAg. Depletion of hepatic macrophages led to CD8+ T cell activation and HBV clearance in the offspring, raising the possibility of targeting macrophages to treat chronic HBV patients.
Children born to mothers who carry HBV often become chronic HBV carriers. By developing a mouse model to study this vertical transmission, Ou and colleagues find that maternal HBV e antigen conditions macrophages of the offspring to suppress the CTL response to HBV, resulting in HBV persistence in the offspring.