Hepatitis B Virus Surface Antigen Activates Myeloid Dendritic Cells via a Soluble CD14-Dependent Mechanism

Abstract

Hepatitis B virus (HBV) infection can cause chronic liver disease, which is associated with increased risk of liver cirrhosis, liver failure, and liver cancer. Clearance of HBV infection requires effective HBV-specific immunity; however, the immunological mechanisms that determine the development of effective HBV-specific immunity are poorly understood. Dendritic cells (DC) play a pivotal role in the regulation of antiviral immunity. Here, we investigated the interaction between HBV surface antigen (HBsAg), the main envelope glycoprotein of HBV, and BDCA1؉ myeloid dendritic cells (mDC). Exposure of peripheral bloodderived BDCA1؉ mDC to HBsAg resulted in strong DC maturation, cytokine production, and enhanced capacity to activate antigen-specific cytotoxic T cells (CTLs). By using neutralizing antibodies, crucial roles for CD14 and Toll-like receptor 4 (TLR4) in HBsAg-mediated BDCA1 ؉ mDC maturation were identified. Concordantly, HBsAg-mediated DC maturation required fetal calf serum (FCS) or human plasma, naturally containing soluble CD14 (sCD14). Intriguingly, HBsAg-induced DC maturation was significantly reduced in umbilical cord blood plasma, which contained less sCD14 than adult plasma, indicating that sCD14 is an important host factor for recognition of HBsAg by DC and subsequent DC activation. A direct interaction between sCD14 and HBsAg was demonstrated by using enzyme-linked immunosorbent assay (ELISA). Moreover, sCD14-HBsAg complexes were detected both in vitro and in sera of HBV-infected patients. The abundance of sCD14-HBsAg complexes varied between chronic HBV disease stages and correlated with activation of BDCA1 ؉ mDC in vivo. We conclude that HBsAg activates BDCA1 ؉ DC via an sCD14-dependent mechanism. These findings provide important novel insights into the initiation of HBV-specific immunity and facilitate development of effective immunotherapeutic interventions for HBV. Hepatitis B virus (HBV) is a double-stranded DNA (dsDNA) virus that is transmitted via blood and specifically infects hepatocytes. It can cause chronic liver disease and progressive liver injury leading to increased risk of liver cirrhosis, liver failure, and liver cancer (1). The current estimated prevalence of HBV infection is 248 million individuals globally (2). Although the initiation of an effective antiviral immune response is paramount for resolving HBV infection (3), the early steps in the recognition of the virus by immune cells and the functional consequences of this interaction remain to be resolved.A pivotal role for dendritic cells (DC) is anticipated, because these cells play a central role in the orchestration of antiviral immunity due to the expression of a wide variety of different pathogen recognition receptors (PRR) and their unique capacity to initiate virus-specific cytotoxic T cell (CTL) responses (4, 5). Among the different DC subsets, BDCA1 ϩ myeloid DC (mDC) are of particular interest for HBV-specific immunity, since hepatitis B surface antigen (HBsAg)-positive mDC were detected in liver (6) an...

Elevated serum levels of soluble CD14 in HBeAg‐positive chronic HBV patients upon Peginterferon treatment are associated with treatment response

“…Possibly, previous studies reporting increased sCD14 levels in CHB included a subset of CHB patients with more severe liver disease, while in our cohort, ~86% treatment‐naive CHB patients have a relative low fibrosis level (<F2 by fibroscan). Furthermore, we here demonstrate that ethnicity influences sCD14 levels which was reported before in rheumatoid arthritis patients and we previously reported the same for age, indicating that also these parameters may be a cause of discrepancy.…”

“…We previously demonstrated that HBsAg can activate Kupffer cells . In addition, we showed that HBsAg‐sCD14 complexes exist in serum of CHB patients and that HBsAg induces dendritic cell activation in a CD14‐dependent manner . Preliminary experiments suggest that PEG‐IFN stimulation may trigger sCD14 release by cultured Kupffer cells especially when HBsAg is present (unpublished data).…”

“…35 In addition, we showed that HBsAg-sCD14 complexes exist in serum of CHB patients and that HBsAg induces dendritic cell activation in a CD14-dependent manner. 25 PEG-IFN has been shown to be effective, that is, achieving immunological control over HBV also after ending of treatment, only in a minority of CHB patients. However, the limited number of patients who respond together with the high costs and side effects makes it essential to select patients who will not benefit from this therapy as early as possible.…”

“…Serum sCD14 was assessed by an in-house-developed ELISA as previously described. 25 Coating antibody was purified rat anti-human sCD14 (clone 55-3, BD Biosciences). Detection antibody was biotinylated anti-human sCD14 (clone 3-C39, BD Biosciences).…”

Interplay between the Hepatitis B Virus and Innate Immunity: From an Understanding to the Development of Therapeutic Concepts

“…In fact, the soluble fraction of CD14, bound to HBsAg, could be responsible for this activation [36]. The fact that the lipid moiety of HBsAg subviral particles is instrumental for this activation represents an interesting finding.…”