Preliminary assessment of hepatitis B-specific cellular immunity amongst a longitudinal vaccine cohort demonstrates evidence of natural exposure. (VAC11P.1110)

Duration of protection after hepatitis B (HB) vaccination is unknown; therefore, we examined humoral and cellular immunity among persons living in an area endemic for HBV, 30 years post-vaccination. Measurement of antibody to hepatitis B surface antigen (anti-HBs) indicated 51% (n=217) of persons retained anti-HBs titer ≥10mIU/mL. However, of persons who lost anti-HBs ( reg , PD-1, CD57, NK/NKT). PD-1 hi CD3 + lymphocytes were significantly increased (p = 0.047) in persons who maintained anti-HBs titer ≥10mIU/mL. Peripheral Blood Mononuclear Cells (PBMC) were stimulated directly ex vivo with whole HB Core Antigen or HB Surface Antigen and assessed for cytokine response. Results indicated no significant difference in the magnitude of HB Surface Antigen-specific responses in persons who maintained anti-HBs ≥10mIU/mL and those who did not. HB Core Antigen-specific TNFα responses were significantly higher (p=0.01) in persons who had lost anti-HBs titer. The observed cellular responses to HB Core suggest natural exposure amongst the cohort. Understanding cellular immunity afforded by the HB vaccine is critical to determining long-term protection.