Hepatitis B virus (HBV)-specific T cells play a key role in
clearance of the virus and in the pathogenesis of liver disease. Peripheral blood (n ؍ 25) and liver biopsies (n ؍ 19) were collected from individuals with chronic untreated HBV infection. Whole blood, cultured peripheral blood mononuclear cells (PBMCs), and cultured liver-infiltrating lymphocytes (LILs) were each stimulated with an overlapping peptide library to the whole HBV genome. The expression of T helper 1 (Th1) cytokines [interferon gamma (IFN-␥), tumor necrosis factor alpha (TNF-␣), and interleukin 2 (IL-2)] and interleukin 10 (IL-10) was analyzed by intracellular cytokine staining and flow cytometry. In ex vivo whole blood, more lymphocytes produced Th1 cytokines than IL-10. When comparing cultured LILs with cultured PBMCs, we found a significantly higher magnitude of CD8 ؉ T cells from the liver producing IL-10 (P ؍ 0.044), primarily in hepatitis B e antigen positive (HBeAg ؉ ) individuals. A positive correlation resulted between the magnitude of HBV-specific TNF-␣ ؉ CD4 ؉ T cells in the liver and the degree of liver inflammation and fibrosis (P ؍ 0.002 and P ؍ 0.006, respectively). Conclusion: The differences in cytokine production from HBV-specific T cells in blood and liver may explain the capacity for HBV to persist in the absence of significant hepatic destruction and highlights the balance between cytokine-mediated viral control and liver damage. (HEPATOLOGY 2007;46:1332-1340.)
H epatitis B virus (HBV)-specific T cells are important in the successful clearance of acute HBV infection but also mediate liver damage in both acute and chronic HBV infections. In individuals with chronic HBV infection, circulating HBV-specific T cells are detected infrequently and are significantly reduced compared with individuals who recover from acute HBV infection. [1][2][3] We recently developed a sensitive method to assess HBV-specific T cells using an overlapping peptide library and intracellular cytokine staining (ICS). 4 However, despite detection of interferon-gamma (IFN-␥) HBV-specific T cells in blood, the magnitude of CD4 ϩ and CD8 ϩ HBV-specific T cells in chronic HBV infection was still significantly lower than that observed in other chronic infections such as human immunodeficiency virus (HIV)-1. 3,4 Previous studies using tetramer staining suggested a larger population of HBV-specific T cells being sequestered within the liver than in circulation. 2,5,6 Although a useful tool to quantify virus-specific T cells, the use of tetramers will detect virus-specific T cells regardless of their function or ability to produce cytokine. 7 In addition, T cells specific for human leukocyte antigen A2-restricted HBV epitopes have been shown to be immunodominant in the peripheral blood of acutely infected individuals who clear HBV, yet immunodominance is not maintained in chronically infected individuals, and exhaustion of T cells is not uniform for all virus-specific T cells. 8,9