Antiviral treatment alters the frequency of activating and inhibitory receptor-expressing natural killer cells in chronic hepatitis B virus infected patients. Mediators Inflamm. 2012;2012:804043. [PMID: 23304062 PMCID: PMC3529875 DOI: 10.1155/2012/804043]

Hepatitis B e Antigen Induces NKG2A+ Natural Killer Cell Dysfunction via Regulatory T Cell-Derived Interleukin 10 in Chronic Hepatitis B Virus Infection

Although persistent hepatitis B virus (HBV) infection is associated with natural killer (NK) cell dysfunction, it remains obscure whether HBV viral antigens are responsible for NK cell dysfunction in patients with chronic hepatitis B (CHB) infection. In this study, we found that the percentage of NK cells expressing the inhibitory receptor, NKG2A, was increased in CHB patients, and NKG2A blockade restored NK cell function. Furthermore, in CHB patients, the frequency of NK cells expressing NKG2A positively correlated with the number of regulatory T cells (Tregs) and production of interleukin-10 (IL-10) in these Tregs. Moreover, exposure of peripheral blood mononuclear cells (PBMCs) isolated from healthy controls to sera from CHB patients resulted in increased proportion of NKG2A⁺ NK cells; IL-10 blockade reduced the frequency of NKG2A⁺ NK cells while increasing the percentage of IFN-γ⁺ NK cells. In addition, stimulation of NK cells and Tregs from healthy controls with CHB sera together with anti-IL-10 antibody increased IFN-γ production in the culture supernatant. The frequencies of NKG2A⁺ NK cells and IL-10⁺ Tregs, along with serum levels of alanine transferase and HBV DNA, were significantly increased in CHB patients positive for the Hepatitis B e antigen (HBeAg, a marker of viral replication) when compared to HBeAg-negative CHB patients. Importantly, exposure of PBMCs from healthy controls to HBeAg resulted in increased IL-10 production but reduced levels of TNF and IFN-γ, and IL-10 blockade rescued the generation of TNF and IFN-γ in this assay. The reduced production of TNF and IFN-γ was also observed in NK cells and Tregs from healthy controls that were stimulated with HBeAg, while IL-10 blockade increased the secretion of these two cytokines. We conclude that HBeAg induces IL-10 production in Tregs, thereby leading to increased expression of NKG2A on NK cells, which contributes to NK cell dysfunction during CHB infection. These data suggest that HBeAg is associated with NK cell dysfunction in CHB.

The effects of nucleoside/nucleotide analogues on host immune cells: the baseline for future immune therapy for HBV?

HBV is a non-cytopathic virus and the progression of liver fibrosis is attributed to the host immune response. Complete suppression of viral replication using nucleotide or nucleoside analogues (NUCs) can prevent most complications related to chronic HBV infection. Unfortunately, antiviral treatment has to be administered lifelong to the majority of patients as HBV persists in the hepatocytes. However, although NUCs are very frequently administered in clinical practice, their effects on vital parts of the host immune response to HBV are not well established. In this review we summarize the currently available data gathered from longitudinal studies that investigated treatment-associated alterations of HBV-specific CD4⁺ and CD8⁺ T-cells, regulatory T-cells and natural killer (NK) cells. These observations are important, as they can guide the design of studies that investigate the efficacy of new immune therapeutic agents. Novel experimental compounds will likely be added to ongoing NUC treatment, which leads to a functional cure in only a small minority of patients.

Natural Killer Group 2A Expressed on Both Peripheral CD3-CD56+NK Cells and CD3+CD8+T Cells Plays a Pivotal Negative Regulatory Role in the Progression of Hepatitis B Virus-Related Acute-on-Chronic Liver Failure

To explore the role of surface receptors natural killer group 2A (NKG2A) and natural killer group 2D (NKG2D) on CD3⁺CD8⁺T cells and CD3^-CD56⁺NK cells in the progression of hepatitis B virus (HBV)-related acute-on-chronic liver failure (ACLF), we measured the expression of NKG2A and NKG2D on the surface of these 2 types of circulating cells by flow cytometry in 3 groups. One group consists of 36 patients with chronic hepatitis B (CHB), another one consists of 22 patients with HBV-related ACLF, and the last one has 12 normal controls (NC). The experimental result indicated that there was no significant difference in the proportion of CD3⁺CD8⁺T cells in total lymphocytes between the 3 groups. However, the percentage of CD3^-CD56⁺NK cells in ACLF group was evidently higher than that in the CHB group (P < 0.05). In addition, the expression of NKG2D on CD3⁺CD8⁺T cells in the ACLF group was significantly lower than that in the CHB group (P < 0.05), but there were no statistically significant differences in its percentages on CD3^-CD56⁺NK cells between the 3 groups. The expression of NKG2A on CD3⁺CD8⁺T cells in the ACLF group was significantly higher than that in the NC group (P < 0.05), and on NK cells was significantly higher than that in the CHB group (P < 0.05) and NC group (P < 0.01). The increase in ratios of NKG2A to NKG2D on CD3⁺CD8⁺T cells and CD3^-CD56⁺NK cells in the ACLF group was significantly more than that in the CHB group and NC group. The results indicate that the imbalance between NKG2A and NKG2D may contribute to the progression of HBV-related ACLF mediated by CD3^-CD56⁺NK cells and CD3⁺CD8⁺T cells. Compared with NKG2D, NKG2A expressed on both peripheral CD3^-CD56⁺NK cells and CD3⁺CD8⁺T cells plays a more pivotal negative regulatory role in the progression of HBV-related ACLF.

Altered Immune Profiles of Natural Killer Cells in Chronic Hepatitis B Patients: A Systematic Review and Meta-Analysis

BACKGROUND

Natural killer (NK) cells are the main effective component of the innate immune system that responds to chronic hepatitis B (CHB) infection. Although numerous studies have reported the immune profiles of NK cells in CHB patients, they are limited by inconsistent results. Thus, we performed a meta-analysis to characterize reliably the immune profiles of NK cells after CHB infection, specifically frequency, phenotype, and function.

METHODS

A literature search of the computer databases MEDLINE, PUBMED, EMBASE, and Cochrane Center Register of Controlled Trails was performed and 19 studies were selected. The standard mean difference (SMD) and 95% confidence interval (CI) of each continuous variable was estimated with a fixed effects model when I2 < 50% for the test for heterogeneity, or the random effects model otherwise. Publication bias was evaluated using Begg's and Egger's tests.

RESULTS

The meta-analysis of publications that reported frequency of peripheral NK cells showed that NK cell levels in CHB patients were significantly lower compared with that of healthy controls. A higher frequency of CD56bright NK subsets was found in CHB patients, but the CD56dim NK subsets of CHB patients and healthy controls were similar. CHB patients before and after antiviral therapy with nucleotide analogues (NUCs) showed no statistical difference in NK frequency. The activating receptors were upregulated, whereas inhibitory receptors were comparable in the peripheral NK cells of CHB individuals and healthy controls. NK cells of CHB patients displayed higher cytotoxic potency as evidenced by CD107a protein levels and conserved potency to produce interferon-gamma (IFNγ), compared with their healthy counterparts.

CONCLUSION

Our results revealed that CHB patients had a lower frequency of NK cells compared with healthy individuals not treatable with antiviral NUC therapy. With an activating phenotype, NK cells in CHB patients showed better cytotoxic potency and conserved IFNγ production.

Histological outcome for chronic hepatitis B patients treated with entecavir vs lamivudine-based therapy

AIM: To compare the histological outcome of chronic hepatitis B (CHB) patients treated with entecavir (ETV) or lamivudine (LAM)-based therapy.

METHODS: We conducted a retrospective analysis of data from 42 CHB patients with advanced fibrosis (baseline Ishak score ≥ 2) or cirrhosis who were treated with ETV or LAM-based therapy in Beilun People’s Hospital, Ningbo between January 2005 and May 2012. The patients enrolled were more than 16 years of age and underwent a minimum of 12 mo of antiviral therapy. We collected data on the baseline characteristics of each patient and obtained paired liver biopsies pre- and post-treatment. The Knodell scoring system and Ishak fibrosis scores were used to evaluate each example. An improvement or worsening of necroinflammation was defined as ≥ 2-point change in the Knodell inflammatory score. The progression or regression of fibrosis was defined as ≥ 1-point change in the Ishak fibrosis score. The continuous variables were compared using t-test or Mann-Whitney test, and the binary variables were compared using χ² test or Fisher’s exact test. The results of paired liver biopsies were compared with a Wilcoxon signed rank test.

RESULTS: Nineteen patients were treated with ETV and 23 patients were treated with LAM therapy for a mean duration of 39 and 42 mo, respectively. After long-term antiviral treatment, 94.74% (18/19) of the patients in the ETV arm and 95.65% (22/23) in the LAM arm achieved an HBV DNA level less than 1000 IU/mL. The majority of the patients (94.74% in the ETV arm and 73.91% in the LAM arm) had normalized ALT levels. The median Knodell necroinflammatory score decreased from 11 to 0 in the patients receiving ETV, and the median Knodell score decreased from 9 to 3 in the patients receiving LAM (P = 0.0002 and < 0.0001, respectively). The median Ishak fibrosis score showed a 1-point reduction in ETV-treated patients and a 2-point reduction in LAM-treated patients (P = 0.0019 and 0.0205, respectively). The patients receiving ETV showed a more significant improvement in necroinflammation than the LAM-treated patients (P = 0.0003). However, there was no significant difference in fibrotic improvement between the two arms. Furthermore, two patients in each arm achieved a fibrosis score of 0 post-treatment, which indicates a full reversion of fibrosis after antiviral therapy.

CONCLUSION: CHB patients with advanced fibrosis or cirrhosis benefit from antiviral treatment. ETV is superior to LAM therapy in improving necroinflammatory but not fibrotic outcome.

Natural killer cells in hepatitis B virus infection

Natural killer cells are a unique type of lymphocytes with cytotoxic capacity, and play important roles against tumors and infections. Recently, natural killer cells have been increasingly valued in their effects in hepatitis B virus infection. Since hepatitis B virus is not cytopathic, the subsequent antiviral immune responses of the host are responsible for sustaining the liver injury, which may result in cirrhosis and even hepatocellular carcinoma. Many studies have confirmed that natural killer cells participate in anti-hepatitis B virus responses both in the early phase after infection and in the chronic phase via cytolysis, degranulation, and cytokine secretion. However, natural killer cells play dichotomic roles: they exert antiviral and immunoregulatory functions whilst contribute to the pathogenesis of liver injury. Here, we review the roles of natural killer cells in hepatitis B virus infection, introducing novel therapeutic strategies for controlling hepatitis B virus infection via the modulation of natural killer cells.