Chronic hepatitis induced by hepatitis B virus (HBV) infection is a serious public health problem, leading to hepatic cirrhosis and liver cancer. Although the currently approved medications can reliably decrease the virus load and prevent the development of hepatic diseases, they fail to induce durable off-drug control of HBV replication in the majority of patients. The roots of Isatis indigotica Fortune ex Lindl., a traditional Chinese medicine, were frequently used for the prevention of viral disease in China. In the present study, (−)-lariciresinol ((−)-LRSL), isolated from the roots of Isatis indigotica Fortune ex Lindl., was found to inhibit HBV DNA replication of both wild-type and nucleos(t)ide analogues (NUCs)-resistant strains in vitro. Mechanism studies revealed that (−)-LRSL could block RNA production after treatment, followed by viral proteins, and then viral particles and DNA. Promoter reporter assays and RNA decaying dynamic experiments indicated that (−)-LRSL mediated HBV RNA reduction was mainly due to transcriptional inhibition rather than degradation. Moreover, (−)-LRSL in a dose-dependent manner also inhibited other animal hepadnaviruses, including woodchuck hepatitis virus (WHV) and duck hepatitis B virus (DHBV). Combining the analysis of RNA-seq, we further found that the decrease in HBV transcriptional activity by (−)-LRSL may be related to hepatocyte nuclear factor 1α (HNF1α). Taken together, (−)-LRSL represents a novel chemical entity that inhibits HBV replication by regulating HNF1α mediated HBV transcription, which may provide a new perspective for HBV therapeutics.

Previous studies have reported that Enterovirus A71 (EV-A71) infection could activate STING-related signaling pathways in vitro, but the role of STING in EV-A71 infection in vivo and the associated immune regulatory mechanisms remain unclear. Here, we used the STING-specific agonist diABZI to activate STING and STING-knockout mice to jointly study the role and mechanism of regulating STING on EV-A71 infection in vivo. The results showed that activating STING could inhibit the in vivo replication of EV-A71, alleviate clinical symptoms in infected mice, and increase the survival rate. Conversely, STING knockout significantly promoted viral replication in vivo and increased the lethality and severity of EV-A71 infection. Mechanistic studies further revealed that STING activation exerts its antiviral effects by stimulating interferon signaling pathways, upregulating the expression of interferon-stimulated genes (ISGs). Additionally, STING activation also modulated the serum cytokine response profile. Moreover, STING activation drove the expansion of diverse immune cell populations, including T cells, natural killer (NK) cells and myeloid cells. In contrast, STING knockout not only reduced the proportion of thymic T cells and impeded T cell developmental progression from double-positive (DP) to single-positive (SP) stages, but also impaired the effector functions of CD8+ T cells and NK cells during viral infection. In summary, this study demonstrates that STING activation effectively suppresses EV-A71 replication and mitigates infection symptoms by modulating immune and inflammatory responses. These findings provide a foundational framework for understanding how STING coordinates antiviral immunity and inform future investigations into STING-targeted therapies for viral infections.

Chronic hepatitis B virus (HBV) infection remains a global public health challenge, and the currently approved medications can not achieve a cure. Synthetic triterpenoids have shown promising therapeutic potential for liver pathologies. In our search for novel antiviral agents against HBV, we found that two triterpenoids, 2-cyano-3,12-dioxooleana-1,9-dien-28-oic acid (CDDO) and CDDO-ethyl amide (CDDO-EA), significantly inhibited HBV DNA replication. Further mechanistic investigation indicated that these two compounds did not significantly alter the levels of total HBV pgRNA, but dramatically reduced extracellular pgRNA and intracellular encapsidated pgRNA in a dose-dependent manner. Western blot analysis indicated minimal effects on core protein expression. Interestingly, using a particle gel assay, we observed that CDDO and CDDO-EA promoted the formation of empty capsids with no alteration in electrophoretic mobility. Moreover, we demonstrated that both compounds modulated the phosphorylation status of the core protein. Further cellular thermal shift assay (CETSA), surface plasmon resonance (SPR) assay, and molecular docking analyses collectively suggested that CDDO and CDDO-EA could bind directly to the dimer–dimer interfaces of HBV core protein. Finally, a synergistic effect was observed between CDDO-EA and lamivudine in reducing intracellular and extracellular HBV DNA levels. Our findings indicate that triterpenoids CDDO and CDDO-EA are new mechanistically type of HBV capsid assembly modulators and warranted for further development as lead compounds against HBV.