Expression of hepatitis B virus x protein in hepatocytes suppresses CD8 T cell activity

The role of regulatory T cells and follicular T helper cells in HBV infection

Hepatitis B has become one of the major global health threats, especially in developing countries and regions. Hepatitis B virus infection greatly increases the risk for liver diseases such as cirrhosis and cancer. However, treatment for hepatitis B is limited when considering the huge base of infected people. The immune response against hepatitis B is mediated mainly by CD8+ T cells, which are key to fighting invading viruses, while regulatory T cells prevent overreaction of the immune response process. Additionally, follicular T helper cells play a key role in B-cell activation, proliferation, differentiation, and formation of germinal centers. The pathogenic process of hepatitis B virus is generally the result of a disorder or dysfunction of the immune system. Therefore, we present in this review the critical functions and related biological processes of regulatory T cells and follicular T helper cells during HBV infection.

Hepatitis B Viral Protein HBx and the Molecular Mechanisms Modulating the Hallmarks of Hepatocellular Carcinoma: A Comprehensive Review

With 296 million cases estimated worldwide, chronic hepatitis B virus (HBV) infection is the most common risk factor for hepatocellular carcinoma (HCC). HBV-encoded oncogene X protein (HBx), a key multifunctional regulatory protein, drives viral replication and interferes with several cellular signalling pathways that drive virus-associated hepatocarcinogenesis. This review article provides a comprehensive overview of the role of HBx in modulating the various hallmarks of HCC by supporting tumour initiation, progression, invasion and metastasis. Understanding HBx-mediated dimensions of complexity in driving liver malignancies could provide the key to unlocking novel and repurposed combinatorial therapies to combat HCC.

Potential of HBx Gene for Hepatocarcinogenesis in Noncirrhotic Liver

Current treatments for hepatitis B virus (HBV) using nucleos(t)ide analogs cannot eliminate the risk of hepatocellular carcinoma (HCC) development. As HBV-associated HCC can develop even in the absence of liver cirrhosis, HBV is regarded to possess direct oncogenic potential. HBV regulatory protein X (HBx) has been identified as a primary mediator of HBV-mediated hepatocarcinogenesis. A fragment of the HBV genome that contains the coding region of HBx is commonly integrated into the host genome, resulting in the production of aberrant proteins and subsequent hepatocarcinogenesis. Besides, HBx interferes with the host DNA or deoxyribonucleic acid damage repair pathways, signal transduction, epigenetic regulation of gene expression, and cancer immunity, thereby promoting carcinogenesis in the noncirrhotic liver. However, numerous molecules and pathways have been implicated in the development of HBx-associated HCC, suggesting that the mechanisms underlying HBx-mediated hepatocarcinogenesis remain to be elucidated.

Beyond Metabolism: Role of the Immune System in Hepatic Toxicity

The liver is primarily thought of as a metabolic organ; however, the liver is also an important mediator of immunological functions. Key perspectives on this emerging topic were presented in a symposium at the 2018 annual meeting of the American College of Toxicology entitled "Beyond metabolism: Role of the immune system in hepatic toxicity." Viral hepatitis is an important disease of the liver for which insufficient preventive vaccines exist. Host immune responses inadequately clear these viruses and often potentiate immunological inflammation that damages the liver. In addition, the liver is a key innate immune organ against bacterial infection. Hepatocytes and immune cells cooperatively control systemic and local bacterial infections. Conversely, bacterial infection can activate multiple types of immune cells and pathways to cause hepatocyte damage and liver injury. Finally, the immune system and specifically cytokines and drugs can interact in idiosyncratic drug-induced liver injury. This rare disease can result in a disease spectrum that ranges from mild to acute liver failure. The immune system plays a role in this disease spectrum.

Pathogenesis of Viral Hepatitis-Induced Chronic Liver Disease: Role of Extracellular Vesicles

Extracellular vesicles are encapsulated lipid nanoparticles secreted by a variety of cell types in living organisms. They are known to carry proteins, metabolites, nucleic acids, and lipids as their cargoes and are important mediators of intercellular communication. The role of extracellular vesicles in chronic liver disease has been reported. Chronic liver disease such as viral hepatitis accounts for a significant mortality and morbidity burden worldwide. Hepatic fibrosis has been commonly associated with the chronic form of viral hepatitis, which results in end-stage liver disease, including cirrhosis, liver failure, and carcinoma in some patients. In this review, we discuss the potential role of extracellular vesicles in mediating communication between infectious agents (hepatitis B and C viruses) and host cells, and how these complex cell-cell interactions may facilitate the development of chronic liver disease. We will further discuss how understanding their biological mechanism of action might be beneficial for developing therapeutic strategies to treat chronic liver disease.

Hepatitis B virus X protein in liver tumor microenvironment

Encoded by the hepatitis B virus, hepatitis B virus X protein (HBx) is a multifunctional, potentially oncogenic protein that acts primarily during the progression from chronic hepatitis B to cirrhosis and hepatocellular carcinoma (HCC). In recent decades, it has been established that chronic inflammation generates a tumor-supporting microenvironment. HCC is a typical chronic inflammation-related cancer, and inflammation is the main risk factor for HCC progression. The viral transactivator HBx plays a pivotal role in the initiation and maintenance of hepatic inflammatory processes through interactions with components of the tumor microenvironment including tumor cells and the surrounding peritumoral stroma. The complex interactions between HBx and this microenvironment are thought to regulate tumor growth, progression, invasion, metastasis, and angiogenesis. In this review, we have summarized the current evidence evaluating the function of HBx and its contribution to the inflammatory liver tumor microenvironment.

Molecular mechanisms of HBeAg in persistent HBV infection

PURPOSE

The aim of this study is to investigate the T-lymphocyte subpopulation and expression of programmed cell death-1 (PD-1), toll-like receptor (TLR)3, TLR4, and interferon (INF)-γ to illustrate the relationship between hepatitis B e antigen (HBeAg) and persistent hepatitis B virus (HBV) infection.

METHODS

Blood was taken from normal subjects into anticoagulation tubes to separate peripheral blood mononuclear cells (PBMCs). The PBMCs were divided into four groups and cultured with various concentrations of HBeAg for 72 h. Changes in the T-cell subset were analyzed through cell counting by flow cytometry, and expression of TLR3, TLR4, and PD-1 was assessed by flow cytometry and Western blot. The concentration of IFN-γ was analyzed using enzyme-linked immunospot (ELISPOT) experiments.

RESULTS

PBMCs were stimulated with various concentrations of HBeAg for 72 h and assayed by flow cytometry to determine CD4+ and CD8+ cell counts. The relative frequencies of CD4+ and CD8+ subpopulations and the CD4+/CD8+ ratio decreased compared with the control group, and T-cell impairment was significantly associated with higher HBeAg load. TLR3, TLR4, and PD-1 protein expression was assessed using flow cytometry and Western blotting. Expression of TLR3, TLR4, and PD-1 increased with increasing concentration of HBeAg. ELISPOT experiments were used to determine the concentration of IFN-γ. IFN-γ production in treatment groups was lower than in the control group. Comparing IFN-γ production in treatment groups, IFN-γ production in PBMCs stimulated with high dose of HBeAg was lower than for those stimulated with low-dose HBeAg.

CONCLUSIONS

HBeAg can inhibit proliferation of lymphocytes, increase TLR3, TLR4, and PD-1 expression, and decrease IFN-γ production. This may be one of the molecular mechanisms of HBV immune tolerance.

Pathophysiological implications of hepatitis B X protein in tumor microenvironment of hepatocellular carcinoma

Hepatitis B X protein (HBx), encoded by hepatitis B virus (HBV), is a multifunctional and potentially oncogenic protein that has significant functions during the progression from chronic hepatitis B to cirrhosis and eventually to hepatocellular carcinoma (HCC). Over the past decades, it has been widely established that chronic inflammation orchestrates a tumor-supporting microenvironment. HCC is a typical chronic inflammation-related cancer and inflammation is the main risk factor for the progression of HCC. As a major viral transactivator, HBx is thought to play a pivotal role in the activation and maintenance of hepatic inflammatory process through interaction with various components of the tumor microenvironment including tumor cell and surrounding peritumoral stroma. Complex interactions between HBx and these cell types in this microenvironment will regulate tumor growth, progression, metastasis, and angiogenesis. In this review, we mainly summarize the current understanding of HBx and its contribution to the inflammatory tumor microenvironment of HBV-related HCC.

Hepatitis B virus X protein accelerates the development of hepatoma

The chronic infection of hepatitis B virus (HBV) is closely related to the occurrence and development of hepatocellular carcinoma (HCC). Accumulated evidence has shown that HBV X protein (HBx protein) is a multifunctional regulator with a crucial role in hepatocarcinogenesis. However, information on the mechanism by which HBV induces HCC is lacking. This review focuses on the pathological functions of HBx in HBV-induced hepatocarcinogenesis. As a transactivator, HBx can modulate nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) and transcription factor AP-2. Moreover, HBx can affect regulatory non-coding RNAs (ncRNAs) including microRNAs and long ncRNAs (lncRNAs), such as miRNA-205 and highly upregulated in liver cancer (HULC), respectively. HBx is also involved in epigenetic modification, including methylation and acetylation. HBx interacts with various signal-transduction pathways, such as protein kinase B/Akt, Wnt/β-catenin, signal transducer and activator of transcription, and NF-κB pathways. Moreover, HBx affects cellular fate by shifting the balance toward cell survival. HBx may lead to the loss of apoptotic functions or directly contributes to oncogenesis by achieving transforming functions, which induce hepatocarcinogenesis. Additionally, HBx can modulate apoptosis and immune response by direct or indirect interaction with host factors. We conclude that HBx hastens the development of hepatoma.

Baculovirus-based Vaccine Displaying Respiratory Syncytial Virus Glycoprotein Induces Protective Immunity against RSV Infection without Vaccine-Enhanced Disease

Background

Respiratory syncytial virus (RSV) is a major cause of severe lower respiratory tract diseases in infancy and early childhood. Despite its importance as a pathogen, there is no licensed vaccine against RSV yet. The attachment glycoprotein (G) of RSV is a potentially important target for protective antiviral immune responses. Recombinant baculovirus has been recently emerged as a new vaccine vector, since it has intrinsic immunostimulatory properties and good bio-safety profile.

Methods

We have constructed a recombinant baculovirus-based RSV vaccine, Bac-RSV/G, displaying G glycoprotein, and evaluated immunogenicity and protective efficacy by intranasal immunization of BALB/c mice with Bac-RSV/G.

Results

Bac-RSV/G efficiently provides protective immunity against RSV challenge. Strong serum IgG and mucosal IgA responses were induced by intranasal immunization with Bac-RSV/G. In addition to humoral immunity, G-specific Th17- as well as Th1-type T-cell responses were detected in the lungs of Bac-RSV/G-immune mice upon RSV challenge. Neither lung eosinophilia nor vaccine-induced weight loss was observed upon Bac-RSV/G immunization and subsequent RSV infection.

Conclusion

Our data demonstrate that intranasal administration of baculovirus-based Bac-RSV/G vaccine is efficient for the induction of protection against RSV and represents a promising prophylactic vaccination regimen.