IL-6 does not disrupt the HBV nucleocapsids. To assess the IL-6 effect on the stability of HBV nucleocapsids, confluent cells were labeled with [35S] methionine-cysteine protein labeling mix for 6 h and then chased in the absence or presence of IL-6 (20 ng/ml or 40 ng/ml) for 24 h or 48 h. Cell lysates were harvested and the nucleocapsids were separated from free core protein by centrifugation through a Centricon-100 filter with a retention cutoff of 100 kDa. Total core protein and nucleocapsids were then immunoprecipitated using an anti-core antibody and separated by SDS-polyacrylamide gel electrophoresis. The labeled core protein was visualized by autoradiography. The signals were quantified by densitometry analysis and expressed as percentage of the respective control cells to indicate the IL-6 effect on capsid stability. Results shown are representative of three independent experiments.