Analysis of HBV-Specific Immune Response in Patients With HBeAg Negative Chronic Hepatitis B Treated With Pegasys (Peginterferon Alfa-2a (40KD)) - Immunology Sub-Study of ML18253

Longitudinal Analysis of HBV-specific T Cell Responses in Patients With HBeAg-negative Chronic Hepatitis B (CHB) Treated With Pegylated Interferon Alfa-2a (40 KD) (Pegasys - RO258310). Immunology Sub-study of ML18253

This study will evaluate immune responses in patients with HBeAg-negative chronic Hepatitis B treated with Pegasys (peginterferon alfa-2a). Eligible patients will have been randomized in study ML18253 to receive Pegasys 180 mcg subcutaneously for 48 or 96 weeks. Sample collection period for each patients will occur in the first 24 weeks.

Inclusion Criteria:

• Adult patients 18-55 years of age
• Chronic HBeAg negative hepatitis B
• Liver disease consistent with chronic hepatitis documented by liver biopsy within 18 months prior to enrollment
• Participation in study ML18253.

Exclusion Criteria:

• Interferon-based or any systemic anti-HBV therapy </= 12 months prior to first dose of study drug
• Antiviral, anti-neoplastic, or immunomodulatory treatment </= 12 months prior to first dose of study drug
• Nonresponders to previous interferon therapy and resistant to lamivudine
• Co-infection with hepatitis A, C or D, or with human immunodeficiency virus (HIV)
• Hepatocellular cancer
• Compensated (Child A, score 6) or decompensated liver disease (Child B or C)
• History or evidence of medical condition associated with chronic liver disease other than HBV