Differential dysfunction in dendritic cell subsets during chronic HCV infection

Hepatitis C virus (HCV) infection is a leading cause of chronic liver disease with over 200 million individuals infected worldwide. The vast majority of acutely infected humans develop chronic infection, which is characterized by attenuated antiviral T-cell responses. The mechanisms leading to such attenuation/suppression are poorly understood. It has been proposed that dysfunction of antigen-presenting cells (APC) may underlie the downregulation of antiviral immune responses. However, studies using bulk or in vitro-derived APC populations have resulted in conflicting reports. In this study, we evaluated the functional and immunophenotypic features of ex vivo-purified dendritic cell (DC) subsets during chronic HCV infection. We found that plasmacytoid DC (PDC) from HCV-infected patients (HCV-PDC) showed a striking deficit in IFN-alpha production in response to CpG stimulation. In addition, we found that myeloid DC (MDC) from these patients showed a diminished capacity to induce a mixed lymphocyte response (MLR), correlating with tower levels of HLA-DR and CD86 expression and higher IL-10 production in response to poly-IC stimulation. In contrast, HCV-PDC showed increased ability to stimulate an MLR. Of note, within the HCV-PDC preparation, we noted a distinctly expanded DC subset that expressed some markers of MDC, but showed significantly lower HLA-DR and CD86 expression, suggesting an expansion of DC at an immature/intermediate stage of differentiation. Our studies demonstrate distinct and contrasting dysfunctional features in DC subsets and underscore the importance of evaluating APC subpopulations separately. (c) 2006 Elsevier Inc. All rights reserved.