DNA IMMUNIZATION INDUCES ANTIBODY AND CYTOTOXIC T-CELL RESPONSES TO HEPATITIS-B CORE ANTIGEN IN H-2(B) MICE

The serum Ab response and the class I-restricted CTL response of C57BL /6 (H-2(b)) mice to hepatitis B (pre)core Ag (HBcAg, HBeAg) was studie d, Injection of HBcAg particles without adjuvants into mice efficientl y primed serum Ab responses but not CTL response. We constructed the e xpression plasmids pCMV-1/c and pCMV-1/e in which expression of HBcAg or HBeAg was driven by cytomegalovirus immediate early region promoter sequences. Stable murine RBL5/C transfectant lines expressing HBcAg w ere established. Intramuscular DNA immunization with plasmid pCMV-1/c (encoding intracellularly expressed core Ag) or pCMV-1/e (encoding sec reted precore Ag) efficiently primed specific serum Ab responses and C TL responses. The CTL response elicited in this system was mediated by CD4(-)CD8(+) effector cells primed in vivo. The CTL recognized the HB cAg(93-100) 8-mer peptide MGLKFRQL in the context of K-b. Hence, DNA i mmunization with HBcAg/HBeAg-expressing plasmids, but not immunization with exogenous HBcAg particles, elicits a class I-restricted CTL resp onse of defined epitope/restriction specificity in H-2(b) mice.