New strategies for the treatment of chronic hepatitis B

Viral sequence determines HLA-E-restricted T cell recognition of hepatitis B surface antigen

The non-polymorphic HLA-E molecule offers opportunities for new universal immunotherapeutic approaches to chronic infectious diseases. Chronic Hepatitis B virus (HBV) infection is driven in part by T cell dysfunction due to elevated levels of the HBV envelope (Env) protein hepatitis B surface antigen (HBsAg). Here we report the characterization of three genotypic variants of an HLA-E-binding HBsAg peptide, Env371-379, identified through bioinformatic predictions and verified by biochemical and cellular assays. Using a soluble affinity-enhanced T cell receptor (TCR) (a09b08)-anti-CD3 bispecific molecule to probe HLA-E presentation of the Env371-379 peptides, we demonstrate that only the most stable Env371-379 variant, L6I, elicits functional responses to a09b08-anti-CD3-redirected polyclonal T cells co-cultured with targets expressing endogenous HBsAg. Furthermore, HLA-E-Env371-379 L6I-specific CD8+ T cells are detectable in HBV-naïve donors and people with chronic HBV after in vitro priming. In conclusion, we provide evidence for HLA-E-mediated HBV Env peptide presentation, and highlight the effect of viral mutations on the stability and targetability of pHLA-E molecules.

Inhibition of hepatic bile salt uptake by Bulevirtide reduces atherosclerosis in Oatp1a1-/-Ldlr-/- mice

Bile salts can strongly influence energy metabolism through systemic signaling, which can be enhanced by inhibiting the hepatic bile salt transporter Na+ taurocholate cotransporting polypeptide (NTCP), thereby delaying hepatic reuptake of bile salts to increase systemic bile salt levels. Bulevirtide is an NTCP inhibitor and was originally developed to prevent NTCP-mediated entry of Hepatitis B and D into hepatocytes. We previously demonstrated that NTCP inhibition lowers body weight, induces glucagon-like peptide-1 (GLP1) secretion, and lowers plasma cholesterol levels in murine obesity models. In humans, a genetic loss-of-function variant of NTCP has been associated with reduced plasma cholesterol levels. Here, we aimed to assess if Bulevirtide treatment attenuates atherosclerosis development by treating female Ldlr-/- mice with Bulevirtide or vehicle for 11 weeks. Since this did not result in the expected increase in plasma bile salt levels, we generated Oatp1a1-/-Ldlr-/- mice, an atherosclerosis-prone model with human-like hepatic bile salt uptake characteristics. These mice showed delayed plasma clearance of bile salts and elevated bile salt levels upon Bulevirtide treatment. At the study endpoint, Bulevirtide-treated female Oatp1a1-/-Ldlr-/- mice had reduced atherosclerotic lesion area in the aortic root that coincided with lowered plasma LDL-c levels, independent of intestinal cholesterol absorption. In conclusion, Bulevirtide, which is considered safe and is EMA-approved for the treatment of Hepatitis D, reduces atherosclerotic lesion area by reducing plasma LDL-c levels. We anticipate that its application may extend to atherosclerotic cardiovascular diseases, which warrants clinical trials.

Hepatitis B virus X protein and TGF-β: partners in the carcinogenic journey of hepatocellular carcinoma

Hepatitis B infection is substantially associated with the development of liver cancer globally, with the prevalence of hepatocellular carcinoma (HCC) cases exceeding 50%. Hepatitis B virus (HBV) encodes the Hepatitis B virus X (HBx) protein, a pleiotropic regulatory protein necessary for the transcription of the HBV covalently closed circular DNA (cccDNA) microchromosome. In previous studies, HBV-associated HCC was revealed to be affected by HBx in multiple signaling pathways, resulting in genetic mutations and epigenetic modifications in proto-oncogenes and tumor suppressor genes. In addition, transforming growth factor-β (TGF-β) has dichotomous potentials at various phases of malignancy as it is a crucial signaling pathway that regulates multiple cellular and physiological processes. In early HCC, TGF-β has a significant antitumor effect, whereas in advanced HCC, it promotes malignant progression. TGF-β interacts with the HBx protein in HCC, regulating the pathogenesis of HCC. This review summarizes the respective and combined functions of HBx and TGB-β in HCC occurrence and development.

The dual role of regulatory T cells in hepatitis B virus infection and related hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is a major contributor to cancer-related deaths worldwide. Hepatitis B virus (HBV) infection is a major etiologic factor leading to HCC. While there have been significant advancements in controlling HBV replication, achieving a complete cure for HBV-related HCC (HBV-HCC) remains an intricate challenge. HBV persistence is attributed to a myriad of mechanisms, encompassing both innate and adaptive immune responses. Regulatory T cells (Tregs) are pivotal in upholding immune tolerance and modulating excessive immune activation. During HBV infection, Tregs mediate specific T cell suppression, thereby contributing to both persistent infection and the mitigation of liver inflammatory responses. Studies have demonstrated an augmented expression of circulating and intrahepatic Tregs in HBV-HCC, which correlates with impaired CD8+ T cell function. Consequently, Tregs play a dual role in the context of HBV infection and the progression of HBV-HCC. In this comprehensive review, we discuss pertinent studies concerning Tregs in HBV infection, HBV-related cirrhosis and HCC. Furthermore, we summarize Treg responses to antiviral therapy and provide Treg-targeted therapies specific to HBV and HCC.

Classifying hepatitis B therapies with insights from covalently closed circular DNA dynamics

The achievement of a functional cure for chronic hepatitis B (CHB) remains limited to a minority of patients treated with currently approved drugs. The primary objective in developing new anti-HBV drugs is to enhance the functional cure rates for CHB. A critical prerequisite for the functional cure of CHB is a substantial reduction, or even eradication of covalently closed circular DNA (cccDNA). Within this context, the changes in cccDNA levels during treatment become as a pivotal concern. We have previously analyzed the factors influencing cccDNA dynamics and introduced a preliminary classification of hepatitis B treatment strategies based on these dynamics. In this review, we employ a systems thinking perspective to elucidate the fundamental aspects of the HBV replication cycle and to rationalize the classification of treatment strategies according to their impact on the dynamic equilibrium of cccDNA. Building upon this foundation, we categorize current anti-HBV strategies into two distinct groups and advocate for their combined use to significantly reduce cccDNA levels within a well-defined timeframe.

Novel Drug Development in Chronic Hepatitis B Infection: Capsid Assembly Modulators and Nucleic Acid Polymers

Currently approved treatment of patients with chronic hepatitis B infection is insufficient to achieve functional cure. Numerous new compounds are identified, and among many, capsid assembly modulators (CAMs) and nucleic acid polymers (NAPs) are 2 classes of virus-directing agents in clinical development. CAMs interfere with viral pregenomic RNA encapsidation and are effective in viral load reduction but have limited effects on hepatitis B surface antigen (HBsAg). NAPs prevent HBsAg release from hepatocytes and induce intracellular degradation, leading to potent suppression of serum HBsAg when combined with nucleoside analogues and pegylated interferon demonstrated by initial data, but awaiting further confirmation studies.