Search

Persistence of hepatitis B virus (HBV) infection is associated with reduced anti-viral T cell responses. Impaired dendritic cell (DC) function was suggested as the cause of reduced T cell stimulation in chronic HBV carriers. Thus, we compared myeloid (mDC) and plasmacytoid DC (pDC) from chronic HBV carriers and controls. Frequency and phenotype of isolated DC were analysed by fluorescence activated cell sorter staining, DC function by mixed lymphocyte reaction, cytokine bead array, intracellular cytokine staining, enzyme-linked immunosorbent assay and enzyme-linked immunospot. Expression of HBV DNA and mRNA was studied by polymerase chain reaction (PCR). Circulating total DC, mDC or pDC were not reduced in chronic HBV carriers. Isolated mDC and pDC from chronic HBV carriers exhibited similar expression of co-stimulatory molecules and alloreactive T helper cell stimulation as control DC, whether tested directly ex vivo or after in vitro maturation. Secretion of pro- and anti-inflammatory cytokines by CD40 or Toll-like receptor ligand-stimulated patient DC was intact, as was human leucocyte antigen A2-restricted HBV-specific cytotoxic lymphocyte stimulation. Although both DC populations contained viral DNA, viral mRNA was undetectable by reverse transcription–PCR, arguing against viral replication in DC. We found no quantitative, phenotypic or functional impairment of mDC or pDC in chronic hepatitis B, whether studied ex vivo or after in vitro maturation. [ABSTRACT FROM AUTHOR]

The aim of this study was to investigate the underlying mechanisms of the genetic association between certain HLA-DRB1* alleles and the immune response to HBsAg vaccination. Therefore, HBsAg peptide binding to HLA-DR molecules was measuredin vitroby peptide binding ELISAs. Additionally, HBsAg-specific T cell reaction and cytokine profile of immune response were analysedex vivoin ELISPOT assays and DR-restriction of T-cell proliferative responses was investigated with HBsAg specific T cell clones. In addition, we compared HBsAg specific T cell responses of 24 monozygotic and 3 dizygotic twin pairs after HBsAg vaccination. Our results showed that the peptide binding assays did not reflect antigen presentationin vivo. DR alleles associated with vaccination failure like DRB1*0301 and 0701 efficiently presented HBsAg peptides. In 11 of 24 investigated monozygotic twin pairs we observed pronounced differences in the recognition of HBsAg peptides. This study indicates that HLA–DR associations with HBsAg vaccination response are not caused by differences in peptide binding or by a shift in the Th1/Th2 profile. Our findings strongly argue for differences in the T cell recognition of peptide/MHC complexes as the critical event in T cell responsiveness to HBsAg. [ABSTRACT FROM AUTHOR]

SUMMARY Insufficient stimulatory capacities of autologous dendritic cells (DC) may contribute in part to impaired T cell stimulation and therefore viral persistence in patients with chronic hepatitis B virus (HBV) infection. In order to characterize the antigen presenting functions of DC from chronic HBV carriers and controls antigen specific T cell responses were analysed. CD34+ peripheral blood progenitor cells were differentiated to immature DC in the presence of GM-CSF, IL-6/IL-6R fusion protein and stem cell factor. Proliferative CD4+ T cell responses and specific cytokine release were analysed in co-cultures of DC pulsed with HBV surface and core antigens or tetanus toxoid and autologous CD4+ T cells. Cultured under identical conditions DC from chronic HBV carriers, individuals with acute resolved hepatitis B and healthy controls expressed similar phenotypical markers but chronic HBV carriers showed less frequent and weaker HBV antigen specific proliferative T helper cell responses and secreted less interferon-γ while responses to the tetanus toxoid control antigen was not affected. Preincubation with recombinant IL-12 enhanced the HBV specific immune reactivities in chronic HBV patients and controls. In conclusion, the weak antiviral immune responses observed in chronic hepatitis B may result in part from insufficient T cell stimulating capacities of DC. Immunostimulation by IL-12 restored the HBV antigen specific T cell responses and could have some therapeutical benefit to overcome viral persistence. [ABSTRACT FROM AUTHOR]

Antibodies directed to the HBs antigen indicate viral clearance and the development of life-long immunity in patients that recovered from HBV infection. In HBs antigen vaccine recipients anti-HBs antibodies provide protective immunity. However, little is known about the regulation of this HBs-specific antibody response. The existence of anti-HBs-secreting B cells was demonstrated using the highly sensitive ELISPOT technique compared with conventional ELISA in serum and cell culture supernatants. In the peripheral blood of patients with acute self-limited hepatitis B, HBs-specific B cells were demonstrated with a high frequency despite undetectable anti-HBs serum antibodies. HBV=immunized patients that had recovered from infection and vaccine recipients had significantly lower frequencies, whereas chronic HBV carriers and negative controls showed no anti-HBs-secreting B cells. Coculture experiments of isolated B and T cells revealed that the anti-HBs antibody response was restricted to the presence of T helper cells, but not to identical HLA class II molecules. Allogeneic T cells derived from vaccine recipients or chronic HBV carriers stimulated the HBs-specific B cell response in HBs vaccine recipients. Otherwise, isolated T helper cells could never provide sufficient help to induce the HBs-specific B cell response in chronic HBV carriers. Furthermore, peripheral blood mononuclear cells (PBMC) of six out of 10 vaccine recipients, one out of five HBV-immunized patients, but of no chronic HBV carrier showed a proliferative response to different HBs antigen preparations. This study demonstrated a high frequency of circulating anti-HBs-producing B cells in the early phase of acute HBV infection, but a lower frequency of HBs-specific B cells years after resolution of HBV infection. In chronic HBV carriers, however, deficient HBs-specific T and B cell responses were observed. [ABSTRACT FROM AUTHOR]