DNA VACCINATION WITH PLASMIDS ENCODING THE INTRACELLULAR (HBCAG) OR SECRETED (HBEAG) FORM OF THE CORE PROTEIN OF HEPATITIS-B-VIRUS PRIMES T-CELL RESPONSES TO 2 OVERLAPPING K-B-RESTRICTED AND K-D-RESTRICTED EPITOPES

Plasmid DNA encoding either the intracellular form HBcAg or the secret ed form HBeAg of the core protein of hepatitis B virus (HBV) was injec ted into the muscle of H-2(b), H-2(d) or F-1(b x d) mice. Serum antibo dy responses and class I-restricted cytotoxic T lymphocyte (CTL) respo nses to HBcAg/ HBeAg were detected in all mice tested, Stable murine H -2(b) and H-2(d) transfectants that express either intracellular HBcAg or secreted HBeAg were constructed, With these cell lines we restimul ated in vitro T cells primed in vivo and detected their specific cytol ytic reactivity against naturally processed peptides. CD8(+) CTL respo nses elicited by DNA vaccination with plasmids encoding HBcAg or HBeAg were specific for the (previously described) K-b-binding HBcAg(93-100 ) peptide MGLKFRQL in H-2(b) mice or the (newly defined) K-d-binding H BcAg(87-95) peptide SYVNTNMGL in H-2(d) mice, The overlapping epitopes span residues 87-100 of HBcAg, and are present on HBcAg and HBeAg, CT L responses were equally well elicited in vivo by injecting HBcAg- or HBeAg-expressing plasmid DNA, and CTL efficiently recognize in vitro H BcAg- and HBeAg-expressing transfectants, DNA vaccination of F-1(b x d ) mice with HBcAg- or HBeAg-expressing plasmid DNA primed CTL populati ons that recognized the K-b- or the K-d-restricted epitope. Both K-b- and K-d-binding peptides are thus generated from cytoplasmic/nuclear H BcAg and secreted HBeAg, These data make it unlikely that the appearan ce of HBeAg-negative variants during chronic HBV infection results fro m CTL-driven selection, DNA vaccination is an efficient technique to p rime CTL responses against overlapping epitopes present on intracellul ar or secreted viral protein antigens.