Multifaceted Defects in Monocytes in Different Phases of Chronic Hepatitis B Virus Infection: Lack of Restoration after Antiviral Therapy.

Monocytes play an important role in the control of microbial infection, but monocyte biology during chronic hepatitis B virus (HBV) infection (CHI) remains inadequately studied. We investigated the frequency, phenotype, and functions of monocyte subsets in different phases of CHI, namely, immune tolerance (IT), hepatitis B early antigen (HBeAg)-positive/HBeAg-negative chronic hepatitis B (EP-/EN-CHB, respectively), and inactive carrier (IC), identified factors responsible for their functional alterations, and determined the impact of antiviral therapy on these cells. Flow cytometric analysis indicated that HLA-DR+ CD14++ CD16- classical monocytes were significantly reduced while HLA-DR+ CD14++ CD16+ intermediate and HLA-DR+ CD14+ CD16++ nonclassical monocytes were expanded in IT and EP-/EN-CHB compared with those in IC and healthy controls (HC). In comparison to IC/HC, monocytes in IT and CHB exhibited diminished expression of Toll-like receptor 2 (TLR-2)/TLR-4/TLR-9 and cytokines interleukin-12 (IL-12)/tumor necrosis factor alpha (TNF-α)/IL-6 but produced higher levels of IL-10/transforming growth factor ß (TGF-ß). Further, monocytes in CHB/IT showed impaired phagocytosis and oxidative response relative to those in IC/HC. In vitro assays indicated that high titers of hepatitis B surface antigen (HBsAg) present in IT/CHB and of IL-4 in CHB triggered the functional defects in monocytes via induction of ß-catenin. Additionally, monocyte-derived M1 macrophages of CHB/IT produced fewer proinflammatory and more anti-inflammatory cytokines than those of IC/HC, while in CHB/IT, the monocytes skewed the differentiation of CD4+ T cells more toward regulatory T cells and a Th2 phenotype. Moreover, monocytes in CHB and IT overexpressed chemokine receptor CCR2, which coincided with increased intrahepatic accumulation of ß-catenin+ CD14+ cells. One year of tenofovir therapy failed to normalize monocyte functions or reduce serum HBsAg/IL-4 levels. Taken together, monocytes are functionally perturbed mostly in IT and EP-/EN-CHB phases. Targeting intramonocytic ß-catenin or reducing HBsAg/IL-4 levels might restore monocyte function and facilitate viral clearance. IMPORTANCE Chronic HBV infection (CHI) is a major cause of end-stage liver disease for which pharmacological treatments currently available are inadequate. Chronically HBV-infected patients fail to mount an efficient immune response to the virus, impeding viral clearance and recovery from hepatitis. Monocytes represent a central part of innate immunity, but a comprehensive understanding on monocyte involvement in CHI is still lacking. We here report a multitude of defects in monocytes in chronically HBV-infected patients that include alteration in subset distribution, Toll-like receptor expression, cytokine production, phagocytic activity, oxidative response, migratory ability, polarization of monocyte-derived macrophages, and monocyte-T-cell interaction. We demonstrated that high levels of hepatitis B virus surface antigen and IL-4 potentiate these defects in monocytes via ß-catenin induction while therapy with the nucleotide analog tenofovir fails to restore monocyte function. Our findings add to the continuing effort to devise new immunotherapeutic strategies that could reverse the immune defects in CHI.

CD8+CD28- T cells: key cytotoxic players impacting disease pathogenesis in chronic HBV infection.

During chronic hepatitis B (CHB), CD8+ T cells down-regulate CD28, the primary co-stimulation molecule for T-cell activation. Diverse functional attributes of CD8+CD28- T cells are suggested in various disease contexts. The present study aimed to characterize CD8+CD28- T cells in different phases of chronic Hepatitis B virus (HBV) infection (CHI)- Immune-tolerance (IT), Hepatitis B e-antigen-positive CHB (EP-CHB), Inactive carriers (IC) and Hepatitis B e-antigen-negative CHB (EN-CHB), to appraise their contribution in HBV-related disease pathophysiology. Flow cytometry analysis of T cells in peripheral blood of study subjects revealed enhanced CD8+CD28- T-cell accumulation in EP-/EN-CHB, compared with IT/IC and they expanded equivalently in HBV-specific and non-specific CD8+ T-cell compartments. Profound increase in CD8+CD28- T cells expressing perforin/granzyme-B/CD57/IFN-γ/TNF-α and markers of terminal differentiation were observed exclusively in EP-/EN-CHB. Further, activation with anti-NKG2D resulted in heightened IFN-γ/TNF-α production selectively from CD8+CD28- T cells, suggesting NKG2D-mediated alternative co-stimulation. CD8+CD28- T cells sorted from CHB patients induced enhanced apoptosis of peripheral blood mononuclear cells (PBMC), including CD4+ T cells. However, NKG2D-ligand (major histocompatibility complex class I chain-related molecule A/B (MICA/B)) was preferentially expressed by HBV-specific CD4+ T cells of CHB patients, making these cells a potential target to NKG2D-dependent CD8+CD28- T-cell killing. Both CD28+ and CD28- T cells in CHB expressed CXCR3 at similar levels and thus capable of homing to the liver. A positive correlation was seen between CD8+CD28- T-cell frequency and serum-alanine transaminase (ALT) levels and CHB-derived CD8+CD28- T cells caused pronounced cell death in HBV-transfected Huh7 cells. Immunofluorescence staining identified greater intrahepatic incidence of CD8+CD28- T cells but decline in CD4+ T cells in CHB than IC. Collectively, CD8+CD28- T cells demonstrated differential distribution and phenotypic/functional skewing in different CHI phases and contribute to disease progression by Perforin-Granzyme- or IFN-γ-TNF-α-mediated cytotoxicity while restraining antiviral immunity through NKG2D-dependent HBV-specific CD4+ T-cell depletion.