OBJECTIVETo observe the changes in hepatitis B virus (HBV)-specific and non-specific cellular immunity that accompany viral load decline during adefovir dipivoxil (ADV) treatment in patients with hepatitis B e antigen (HBeAg)-positive chronic hepatitis B, and to explore the antiviral immunity mechanism underlying the treatment response.

METHODSSerial analysis of cellular immunological parameters was performed in HBeAg-positive patients (n = 20) throughout the 48-week course of ADV therapy (10 mg/d). HBV-specific T cell reactivity to HBV core antigen (HBcAg) was assessed by enzyme-linked immunosorbent spot assay and cell proliferation assay at pre-treatment (baseline) and post-treatment weeks 4, 12, 24, 36, and 48. Percentage of regulatory T cells (Tregs), as well as activated peripheral natural killer (NK) cells (expressing the NKG2D receptor), was measured by flow cytometry. Comparisons of means were performed by the two-tailed t-test or the Mann-Whitney rank sum test.

RESULTSAfter 48 weeks of ADV therapy, HBeAg loss was observed in six of the 20 (30%) patients and 14 patients remained HBeAg-positive. In the patients with HBeAg loss, the viral load reduction was accompanied by a significantly enhanced response rate of HBV-specific interferon (IFN)-gamma-producing CD4+ T cells [measured as (spot forming cells/peripheral blood mononuclear cells); baseline: (661.25+/-281.97) *10(-6) vs. week 48: (280.75+/-104.33) *10(-6), P = 0.045]. In contrast, patients without HBeAg loss showed no significant differences in T cell response rates. The patient groups with and without HBeAg loss showed similar proportions of peripheral blood Tregs during the treatment course, which included a trend of gradual decrease from baseline to week 4 with steady levels thereafter. In addition, both groups showed a similar increase in NKG2D expression that began at week 12 and peaked at week 48.

CONCLUSIONHBV-specific T cell reactivity temporally increases in some ADV-treated chronic hepatitis B patients, and this trend is strongly associated with HBeAg loss. Furthermore, recovery of HBV-specific T cell reactivity promotes viral clearance and HBeAg seroconversion.