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In chronic hepatitis C virus (HCV) infection, combination therapy of peginterferon and ribavirin does not guarantee viral eradication. Among factors relevant to therapeutic efficacy, the role of humoral immunity has not been examined thoroughly. In the current study, HCV pseudoparticles (HCVpp) were first generated with 80 patient-derived full-length HCV envelope clones, followed by detailed characterization with regard to virus productivity, infectivity and neutralizing activity. Selective HCVpp were used to measure HCV neutralization titers in two independent patient cohorts consisting of 102 patients undergoing antiviral therapy. The HCV neutralization titers at the baseline fitted with a power-law distribution among patients. Pretreatment neutralization titers in both patient cohorts were not correlated with treatment outcomes. In the patient cohort 2 (n = 28) that had samples available at multiple time points, however, HCV neutralization titers displayed clearly distinct patterns over therapeutic course and follow-up. No virological responders (n = 10) had neutralization titers stabilized at low level while it was increased significantly in both sustained virological responders (n = 10) and relapsers (n = 8). High HCV neutralization titers were maintained only in sustained virological responders but not in relapsers after treatment cessation. Therefore, patterns of longitudinal change of HCV neutralization titers, but not pretreatment titers, correlate with the treatment outcome in patients undergoing peginterferon and ribavirin combination therapy. J. Med. Virol. 87:821–828, 2015. © 2015 Wiley Periodicals, Inc.