Charriaud, F. | bioRxiv Science

bioRxiv2026

Preclinical antiviral study of a liver-targeted TLR1/2 agonist in an immune-competent mouse model of HBV infection

Chronic hepatitis B cure requires the inactivation and/or elimination of covalently closed circular DNA (cccDNA), together with silencing of integrated viral genomes and restoration of HBV-specific immune responses. The TLR1/2 agonist Pam3CSK4 has previously been identified as a potent direct anti-HBV agent in vitro. In the present study, we engineered a liver-targeting polymeric nanoparticle formulation of Pam3CSK4 to enhance its in vivo immunostimulatory and antiviral activity. We evaluated the antiviral efficacy of this novel nanoformulation carrying the TLR1/2 agonist (NP-Pam3CSK4) in monotherapy and started to investigate its mechanism of action through immunological correlates in an immune-competent AAV-HBV mouse model. AAV-HBV-infected mice received intravenous administrations of NP-Pam3CSK4 at doses of 5 or 20 g twice per treatment cycle over four cycles, followed by a 2-week follow-up period. Soluble Pam3CSK4 was administered at substantially higher doses (100 g). Serial blood samples were regularly collected to monitor virological and host immune parameters. At study completion, liver tissues were harvested for intrahepatic quantification of viral and immunological markers using immunoassays, quantitative PCR, and histological analyses. The most pronounced antiviral effects were observed in mice treated with NP-Pam3CSK4 formulations, which achieved greater viral suppression than free Pam3CSK4 despite markedly lower administered doses. Histological examination of liver biopsies from treated animals revealed prominent immune cell infiltration, including macrophages, monocytes, and T cells, organized in dense cluster-like structures. These findings support the induction of coordinated innate and adaptive immune responses contributing to HBV control and clearance. Collectively, our results demonstrate that nanoparticle-based delivery of TLR1/2 agonist represents a promising therapeutic strategy for chronic HBV infection and may improve the likelihood of achieving functional cure. Further mechanistic and translational studies (combination) are warranted to support clinical development.

microbiology↗

bioRxiv2026

Ritonavir-Induced Cellular Stress Alters Viral HBs Glycoprotein Biogenesis and Production of Infectious Hepatitis D Virions

Chronic co-infections by HBV and its satellite virus HDV are associated with a high risk of progression to cirrhosis and liver cancer, and therapeutic options for achieving a cure are still unsatisfactory. HBs is the main surface glycoprotein of both viruses, and is also massively secreted by infected hepatocytes in the form of empty subviral particles which suppress the host immune responses. This makes HBs an attractive target to develop therapeutic strategies. Here, we took advantage of the known interaction between the Large form HDV antigen (HDAg-L) and the small form of HBs (S-HBs) to develop a non-infectious, minimalistic reporter assay for the assembly and secretion of HDV particles. By screening the existing pharmacopeia for drugs that could interfere with S-HBs and HDAg-L co-secretion, we found that ritonavir and other Cytochrome P450 inhibitors affect the biogenesis of HBs and impair the production of infectious HDV virions. Mechanistically, we established that these drugs induce oxidative stress which dysregulates disulfide bond formation in the endoplasmic reticulum. As a consequence, the production of HBs, which depends on a dense network of disulfide bonds, is markedly affected as evidenced by an abnormal glycosylation profile, altered antigenic properties, and a poor expression of the largest form of HBs (L-HBs) which is essential to virus entry into target cells. This is associated with induction of the unfolded protein response, with the upregulation of CHOP/DDIT3 and key enzymes involved in the synthesis of the reducing metabolite glutathione (PHGDH, SHMT2, MTHFD2). Overall, our results indicate that alterations in redox homeostasis significantly impact HBs biogenesis, and reveal a druggable pathway that could be exploited to eliminate HDV in chronically infected patients. IMPACT AND IMPLICATIONSMore effective therapies are still needed to achieve a functional cure in patients chronically co-infected by HBV and HDV. In this study, we discovered that ritonavir, along with other cytochrome P450 inhibitors, can affect the production of infectious HDV particles in human hepatocyte cultures. Mechanistically, ritonavir induces oxidative stress and the unfolded protein response in the endoplasmic reticulum, thereby altering the biogenesis of HBs, the surface glycoprotein of both viruses. This work highlights the potential benefit and mechanism of action of ritonavir and related molecules in the treatment of co-infected patients.

microbiology↗