Occupational exposure to hepatitis C virus: early T-cell responses in the absence of seroconversion in a longitudinal cohort study.

Background: T-cell responses have been described in seronegative patients who test negative for hepatitis C virus (HCV) RNA despite frequent HCV exposure. However, the cross-sectional design of those studies did not clarify whether T cells were indeed induced by low-level HCV exposure without seroconversion or whether they resulted from regular acute infection with subsequent antibody loss.

Methods: Over a 10-year period, our longitudinal study recruited 72 healthcare workers with documented HCV exposure.

Effects of antiviral therapy on the cellular immune response in acute hepatitis C.

Spontaneous recovery occurs in a minority of patients with acute hepatitis C but is associated with vigorous and long-lasting cellular immune responses. Treatment-induced recovery can be achieved in the majority of patients who are treated in the acute phase, but the kinetics and mechanisms of viral clearance and immune responsiveness are not known. Both direct antiviral effects and indirect immune-mediated effects, such as immune modulation of Th2 to Th1 responses and prevention of exhaustion of cellular responses by rapid reduction of viral titer, have been proposed.

Functional expression of the chemokine receptor CCR5 on virus epitope-specific memory and effector CD8+ T cells.

Because the chemokine receptor CCR5 is expressed on Th1 CD4(+) cells, it is important to investigate the expression and function of this receptor on other T cells involved in Th1 immune responses, such as Ag-specific CD8(+) T cells, which to date have been only partially characterized. Therefore, we analyzed the expression and function of CCR5 on virus-specific CD8+ T cells identified by HLA class I tetramers. Multicolor flow cytometry analysis demonstrated that CCR5 is expressed on memory (CD28+CD45RA-) and effector (CD28-CD45RA- and CD28-CD45RA+) CD8+ T cells but not on naive (CD28+CD45RA+) CD8+ T cells.

The role of hepatitis B virus-specific memory CD8 T cells in the control of viral replication.

Background/aims: The aim of this study is to clarify the differences of host immune responses between acute self-limited and chronic persistent hepatitis B virus (HBV) infections by quantitative and qualitative analysis of HLA-A*2402-restricted HBV-specific CD8+ T cells.

Methods: HBV-specific CD8+ T cells in peripheral blood mononuclear cells (PBMCs) from patients infected with HBV were analyzed by flow cytometry using two HLA-A*2402-HBV peptide tetrameric complexes.

Results: High numbers of HBV-specific CD8+ T cells were detected in acute phase PBMCs from most individuals with acute HBV infection while the number of these cells was greatly reduced in recovery phase PBMCs.