Chronic hepatitis B virus (HBV) infection is a major health problem, affecting around 254 million people worldwide. Current treatments have side effects and can lead to resistance. Therefore, natural compounds derived from plants are being studied as potential antivirals. Isochlorogenic acid A (ICAA), which is derived from caffeoylquinic acid, exerts antiviral and hepatoprotective effects. The antioxidant effect of ICAA, triggered by upregulation of heme oxygenase 1 (HO-1), has been suggested as potential antiviral mechanism. However, the underlying mechanisms remain enigmatic. Our aim is to elucidate the mode of action of the antiviral effect of ICAA on HBV. Stable or transient transfected cells expressing HBV as well as HBV-infected cells were instrumental. (Sub)viral particles were characterized by biophysical and biochemical methods. Subcellular distribution of viral proteins was studied using confocal laser scanning microscopy. Viral genomes and transcripts were quantified by qPCR. Treatment with ICAA decreased levels of HBV surface and e antigens (HBsAg and HBeAg), as well as viral transcripts, genomes and most important cccDNA. Furthermore, impaired virus assembly was evident from accumulation of naked capsids suggesting improper capsid formation and impaired envelopment. ICAA-dependent effects on HBV correlate with upregulation of HO-1 and modulation of intracellular ROS Our data indicate a possible link between changes in the intracellular ROS level and altered free -SH groups in viral structural proteins, possibly influencing proper disulphide bond formation and thereby assembly. In conclusion ICAA-dependent effects on HBV life cycle are based on several pillars as modulation of intracellular ROS and impaired morphogenesis and replication.
Koyaweda et al. (2025) studied this question.