Antigen-presenting dendritic cells (DCs), which play a major role in the triggering of primary anti viral immune reactions, may also contribute, in some viral models, to the pathogenesis of persistent viral infection. In fact, impaired immune response to hepatitis B virus (HBV)-encoded antigens is seen in patients with chronic hepatitis B (CH-B). The aim of this study was to check the function of DCs in these patients and to investigate the underlying mechanism. DCs were enriched from peripheral blood mononuclear cells by culturing with interleukin (IL)-4 and granulocyte-macrophage colony stimulating factor for 7 days. The stimulatory capacity of DCs were checked in allogenic mixed leukocyte (MLR) reaction. The levels of IL-12 in the culture supernatants were measured by an enzyme-linked immunosorbent assay. HBV DNA and HBV RNA were localized in DCs by polymerase chain reaction (PCR) in situ hybridization and reverse-transcriptase (RT)-PCR in situ hybridization. The stimulatory capacity of DCs in allogenic MLR was significantly lower in patients with CH-B (36321±12523 cpm, n=18) compared to that of normal controls (65678±11174 cpm, n=18) (p<0.0001). Significantly lower levels of IL-12 were detected in cultures containing DCs from patients with CH-B than normal controls (46.7±25.6 versus 122.4± 37.1 pg/ml, p<0.0001). In situ hybridization revealed the localization of HBV DNA and HBV RNA in DCs from patients with CH-B. These results indicate that chronic infection by HBV is associated with functional defects of DCs. Localization of HBV DNA and HBV RNA indicates that DCs may constitute an extra hepatic reservoir and possibly of replication of HBV.

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