Table 1. HBsAg-specific cellular immune response in vaccinated normal C57BL/6 mice.

Mouse	Numbers	Positivity (%)	SI
DNA-vaccinated normal mouse	10	10 (100%)	5·9 ± 1·2*
(serum anti-HBs (+ve))
DNA-vaccinated normal mouse	5	2 (40%)	2·9, 3·1
(serum anti-HBs (–ve))

Normal C57BL/6 mice were injected with a single injection of 100 µg of pCAGGS(S). Spleen cells from 10 mice seropositive for anti-HBs and 5 mice seronegative for anti-HBs were cultured with HBsAg for 120 hr. The incorporation of [³H]thymidine during the final 12 hr of culture were measured as c.p.m. HBsAg-specific T lymphocyte proliferation was determined from the stimulation index (SI), which was calculated as the c.p.m. of cultures containing HBsAg divided by the c.p.m. of cultures without HBsAg. An SI value of > 2·0 indicated significant HBsAg-specific proliferation.

^*Mean±SD.