The hepatitis B virus (HBV) core protein has been found in the nucleus, the cytoplasm, or both of HBV-infected hepatocytes. nuclear localization of the HBV core protein is negatively regulated by phosphorylation during the cell cycle.
HBcAg (core antigen) is a hepatitis B viral protein. It is an indicator of active viral replication; this means the person infected with Hepatitis B can likely transmit the virus on to another person.