MiR-146a secreted via EVs modulates TLR9 signalling in a cell model of chronic HBV infection

Abstract

Hepatitis B virus (HBV) infection remains a major global health threat, with more than 250 million people chronically infected and at risk of cirrhosis and hepatocellular carcinoma. Infected hepatocytes release large amounts of defective, non-infectious viral particles, while only a small fraction (around 10%) is infectious. However, HBV itself does not directly trigger a strong immune response. Interferon-α (IFNα) is a key antiviral cytokine produced upon activation of Toll-like receptor 9 (TLR9). This pathway is negatively regulated by microRNA-146a (miR-146a), whose expression is elevated in patients with chronic HBV infection. We hypothesized that HBV-infected hepatocytes secrete extracellular vesicles (EVs) enriched in miR-146a, which are subsequently taken up by immune cells to suppress antiviral signalling. Consistent with this, the HBV-producing hepatoma cell line expressed significantly higher levels of miR-146a, both intracellularly and within secreted EVs, compared with control cells. Furthermore, peripheral blood mononuclear cells (PBMCs) exposed to EV-containing conditioned media from HBV-producing hepatoma cells exhibited impaired TLR9 responses, whereas HBV itself failed to activate TLR9. This suggests, that miR-146a could be the mediator of the TLR9 signalling inhibition, which will be further verified using miR-146a inhibitor. Collectively, these findings suggest, that EVs could be important mediators of HBV-induced immune deregulation and highlight EV-associated miR-146a as both a potential biomarker and a therapeutic target in chronic HBV infection.