Characterization of cell mediated immune responses to the hepatitis B core protein in man

Eight donors immune to hepatitis B (HB) after natural infection were studied for their cell-mediated immune response to hepatitis B core (HBc) protein in vitro. Significant specific activation was observed in highly purified peripheral blood lymphocytes and T cells from these donors after 5-8 days of incubation with HBc protein. This in vitro response was modulated by monocytic cells and maximal 3H-thymidine incorporation was elicited with low concentrations of the antigen (0.1-10 ng/ml). The cell-mediated immune reactivity towards HBc-protein was significantly (P less than 0.005) elevated compared to the envelope material of the virus (HBsAg) when analysed in the same donor population. In contrast, donors with plasma-derived hepatitis B vaccine induced immunity to HB exhibited only specific lymphocyte activation to HBsAg. These data indicate that the composition of immune responses conferring protection against HBV after natural infection is far more complex than after immunization with the hepatitis B vaccine. Further characterization of the cell-mediated immune response to HBc protein and its relation to protection against HBV seems warranted when strategies for new HB-vaccines are being designed.