High frequency of circulating HBcAg-specific CD8 T cells in hepatitis B infection: a flow cytometric analysis

Viral antigen-specific T cells are important for virus elimination. We stud ied the hepatitis B virus (HBV)-specific T cell response using flow cytomet ry. Three phases of HBV infection were studied: Group A, HBeAg (+) chronic hepatitis; Group B, HBeAb (+) HBV carrier after seroconversion; and Group C , HBsAb (+) phase. Peripheral T cells were incubated with recombinant HB co re antigen (HBcAg), and intracytoplasmic cytokines were analysed by flow cy tometry. HBcAg-specific CD4 and CD8 T cells were identified in all three gr oups and the number of IFN-gamma -positive T cells was greater than TNF-alp ha -positive T cells. The frequency of IFN-gamma -positive CD4 and CD8 T ce lls was highest in Group C, compared with Groups A and B. No significant di fference in the HBcAg-specific T cell response was observed between Group A and Group B. The HBcAg-specific CD8 T cell response was diminished by CD4 depletion, addition of antibody against human leucocyte antigen (HLA) class I, class II or CD40L. Cytokine-positive CD8 T cells without HBcAg stimulat ion were present at a high frequency (7 of 13 cases) in Group B, but were r are in other groups. HBcAg-specific T cells can be detected at high frequen cy by a sensitive flow cytometric analysis, and these cells are important f or controlling HBV replication.