Hepatitis A virus-specific humoral and cellular immune responses following immunization with a formalin-inactivated hepatitis A vaccine.

To evaluate proliferative T cell responses elicited by a formalin-inactivated HAV vaccine, we immunized 10 subjects with an inactivated HAV vaccine, and measured HAV antibody titers and HAV-specific T cell proliferation. gamma-Interferon production by PBMC's was evaluated in selected subjects. By week 30, seroconversion (geometric mean titer=2299 mIU/ml), and HAV-specific proliferation was detected in all subjects. HAV also induced gamma-interferon in the three subjects studied. These data indicate that the inactivated HAV vaccine induces proliferative T cell responses in addition to HAV antibody. This may be important for protection against hepatitis A, and suggests that recall memory for HAV antigen is elicited by the vaccine.