The hepatitis B virus e antigen suppresses the respiratory burst and mobility of human monocytes and neutrophils. Immunobiology. 2014;219:880-887. [PMID: 25123430 DOI: 10.1016/j.imbio.2014.07.008]

HBeAg induces neutrophils activation impairing NK cells function in patients with chronic hepatitis B

BACKGROUND

The role of neutrophils in hepatitis B virus (HBV) infection has been a subject of debate due to their involvement in antiviral responses and immune regulation. This study aimed to elucidate the neutrophil characteristics in patients with chronic hepatitis B (CHB).

METHODS

Through flow cytometry and ribonucleic acid-sequencing analysis, the phenotypes and counts of neutrophils were analyzed in patients with CHB. Moreover, the effects of HBeAg on neutrophils and the corresponding pattern recognition receptors were identified. Simultaneously, the cross-talk between neutrophils and natural killer (NK) cells was investigated.

RESULTS

Neutrophils were activated in patients with CHB, characterized by higher expression levels of programmed death-ligand 1 (PD-L1), cluster of differentiation 86, and interleukin-8, and lower levels of CXC motif chemokine receptor (CXCR) 1 and CXCR2. Hepatitis B e antigen (HBeAg) partially induces neutrophil activation through the Toll-like receptor 2 (TLR2). A consistent upregulation of the TLR2 and HBeAg expression was observed in patients with CHB. Notably, the genes encoding molecules pivotal for NK-cell function upon NK receptor engagement enriched in neutrophils after HBeAg activation. The HBeAg-activated neutrophils demonstrated the ability to decrease the production of interferon-gamma (IFN-γ) and tumor necrosis factor-alpha (TNF-α) in NK cells, while the PD-1 and PD-L1 pathways partially mediated the immunosuppression.

CONCLUSIONS

The immunosuppression of neutrophils induced by HBeAg suggests a novel pathogenic mechanism contributing to immune tolerance in patients with CHB.

Immune response and treatment targets of chronic hepatitis B virus infection: innate and adaptive immunity

Chronic hepatitis B virus (HBV) infection is a major global public health risk that threatens human life and health, although the number of vaccinated people has increased. The clinical outcome of HBV infection depends on the complex interplay between viral replication and the host immune response. Innate immunity plays an important role in the early stages of the disease but retains no long-term immune memory. However, HBV evades detection by the host innate immune system through stealth. Therefore, adaptive immunity involving T and B cells is crucial for controlling and clearing HBV infections that lead to liver inflammation and damage. The persistence of HBV leads to immune tolerance owing to immune cell dysfunction, T cell exhaustion, and an increase in suppressor cells and cytokines. Although significant progress has been made in HBV treatment in recent years, the balance between immune tolerance, immune activation, inflammation, and fibrosis in chronic hepatitis B remains unknown, making a functional cure difficult to achieve. Therefore, this review focuses on the important cells involved in the innate and adaptive immunity of chronic hepatitis B that target the host immune system and identifies treatment strategies.

The Complex Role of HBeAg and Its Precursors in the Pathway to Hepatocellular Carcinoma

Hepatitis B virus (HBV) is one of the seven known human oncogenic viruses and has adapted to coexist with a single host for prolonged periods, requiring continuous manipulation of immunity and cell fate decisions. The persistence of HBV infection is associated with the pathogenesis of hepatocellular carcinoma, and various HBV proteins have been implicated in promoting this persistence. The precursor of hepatitis e antigen (HBeAg), is translated from the precore/core region and is post-translationally modified to yield HBeAg, which is secreted in the serum. HBeAg is a non-particulate protein of HBV and can act as both a tolerogen and an immunogen. HBeAg can protect hepatocytes from apoptosis by interfering with host signalling pathways and acting as a decoy to the immune response. By evading the immune response and interfering with apoptosis, HBeAg has the potential to contribute to the hepatocarcinogenic potential of HBV. In particular, this review summarises the various signalling pathways through which HBeAg and its precursors can promote hepatocarcinogenesis via the various hallmarks of cancer.

Hepatitis B virus e antigen and viral persistence

Hepatitis B virus (HBV) e antigen (HBeAg) was discovered in the sera of HBV patients nearly 50 years ago. It is not essential for HBV to infect or replicate in hepatocytes. Earlier clinical studies suggested that this antigen might play an important role for HBV to establish persistence in babies after its mother-to-child transmission. Subsequent clinical studies also suggested that HBeAg might have immunomodulatory activities. In recent years, a large body of information on how HBeAg might modulate host immunity was published. In this review, we summarize recent research progresses on the immunomodulatory activities of HBeAg and discuss how these activities of HBeAg may promote HBV persistence.

Direct Inhibition of Hepatitis B e Antigen by Core Protein Allosteric Modulator

Hepatitis B e antigen (HBeAg) is an important immunomodulator for promoting host immune tolerance during chronic hepatitis B (CHB) infection. In patients with CHB, HBeAg loss and seroconversion represent partial immune control of CHB infection and are regarded as valuable endpoints. However, the current approved treatments have only a limited efficacy in achieving HBeAg seroconversion in HBeAg-positive patients. Hepatitis B virus (HBV) core protein has been recognized as an attractive antiviral target, and two classes of core protein allosteric modulator (CpAM) have been discovered: the phenylpropenamides (PPAs) and the heteroaryldihydropyrimidines (HAPs). However, their differentiation and potential therapeutic benefit beyond HBV DNA inhibition remain to be seen. Here, we show that in contrast to PPA series compound AT-130, a HAP CpAM, HAP_R01, reduced HBeAg levels in multiple in vitro and in vivo HBV experimental models. Mechanistically, we found that HAP_R01 treatment caused the misassembly of capsids formed by purified HBeAg in vitro. In addition, HAP_R01 directly reduces HBeAg levels by inducing intracellular precore protein misassembly and aggregation. Using a HAP_R01-resistant mutant, we found that HAP_R01-mediated HBeAg and core protein reductions were mediated through the same mechanism. Furthermore, HAP_R01 treatment substantially reduced serum HBeAg levels in an HBV mouse model. Conclusion: Unlike PPA series compound AT-130, HAP_R01 not only inhibits HBV DNA levels but also directly reduces HBeAg through induction of its misassembly. HAP_R01, as well as other similar CpAMs, has the potential to achieve higher anti-HBeAg seroconversion rates than currently approved therapies for patients with CHB. Our findings also provide guidance for dose selection when designing clinical trials with molecules from HAP series.

Hepatitis B Virus e Antigen Regulates Monocyte Function and Promotes B Lymphocyte Activation

Hepatitis B virus (HBV) e (HBe) antigen is a nonstructural virus component with great immune regulation roles. It regulates adaptive immunity response and participates in persistent infection development. However, its roles on monocytes and B lymphocytes were rarely studied. Herein, we studied HBe roles on U937 and Hmy2.CIR by creating HBe stably transfected cells using lentivirus. We detected the motility of HBe-U937 through transwell migration assay. Cytokines that primarily produced by monocytes, including BAFF, B-cell activating factor (BAFF), interleukin (IL)-6, IL-10, tumor necrosis factor (TNF)-α, and A proliferation inducing ligand (APRIL), were measured in culture supernatants of transfected U937, and serum BAFF, IL-6, and IL-10 were detected in HBe-positive and HBe-negative HBV-infected patients. Among these, BAFF mRNA and membrane-bound BAFF were further detected. Activation and inhibition markers of B lymphocytes on HBe-Hmy2.CIR and proliferation of transfected Hmy2.CIR after coculture with transfected U937 were also detected. We found that U937 migration was inhibited by HBe. BAFF expression was increased in HBe-U937, however, membrane-bound BAFF on HBe-U937 was decreased. In addition, Serum BAFF in HBe-positive patients was higher than in HBe-negative patients. IL-6 and IL-10 were increased in HBe-U937 after being stimulated by lipopolysaccharide (LPS), however, serum IL-6 and IL-10 were not associated with HBe status in patients. Besides, TNF-α and APRIL expression were basically the same in GV166-U937 and HBe-U937. B lymphocyte activation markers CD86 and Tspan33 were raised in HBe-Hmy2.CIR. However, inhibition markers Lyn and CD32b had no differences between HBe-Hmy2.CIR and control. Proliferation of transfected Hmy2.CIR was not affected by coculture with transfected U937, however, HBe transfection itself enhanced Hmy2.CIR proliferation. Altogether, these revealed that HBe can inhibit U937 migration and promote cytokines, including BAFF, IL-6, and IL-10, production in U937. Besides, HBe enhances BAFF release from U937 and increases BAFF concentration in vivo. In addition, HBe antigen facilitates Hmy2.CIR activation and proliferation through direct induction.

Neutrophil dysfunction in patients with liver cirrhosis

Liver cirrhosis is the final stage of chronic liver disease of any causes, in which the defensive reaction to infections is reducing. Patients with liver cirrhosis are at an increased risk of infections, sepsis and death. Neutrophils are an essential component of the innate immune response and the first line of defense to resist all kinds of detrimental factor, and participate in specific immunity. Immune dysfunction in cirrhosis is associated with neutrophil dysfunction. This paper reviews the neutrophil dysfunction and its pathogenesis in liver cirrhosis.