Preclinical evaluation of a two-dose vaccination schedule of recombinant Hansenula polymorpha hepatitis B vaccine in animals.

AIMS

The current 3-dose regimen of hepatitis B vaccination for infants requiring over 6 mo period may pose the poor rate of compliance and later protection from hepatitis B virus (HBV) infection. This preclinical study is to investigate the feasibility of reducing the number of doses of hepatitis B (HB) vaccine.

RESULTS

Eight groups of guinea pigs immunized with two doses of HP-HB vaccines at either 0 and 4 weeks or 0 and 8 weeks elicited geometric titers (GMT) of anti-HBs similar to that of four groups immunized with three doses of controls. The overall GMT of anti-HBs were not significantly different between the E- and C-groups (p>0.05) of monkeys. Specifically, the anti-HBs titers in the C-group reached the peak of 24857 (938.3-104585) mIU/mL one week after the 3rd dose, which were statistically higher than those of the E-group. However, they were reduced to comparable levels of anti-HBs in the E-group during weeks 9-12, suggesting comparable immune response of both vaccination regimens.

METHODS

Twelve groups of guinea pigs (four animals in each group) were immunized with 2 experimental recombinant yeast Hansenula Polymorpha derived HB vaccines (HP-HB vaccine) and 2 commercial recombinant yeast Saccharomyces Cerevisiae vaccines (Temrevac-HB) as controls at 0, 4 and 8 weeks, 0 and 4 weeks, and 0 and 8 weeks respectively. Each guinea pig received 2 µg vaccine. Twelve Cynomolgus monkeys were randomly divided into two groups (six animals in each group). Animals in the experimental group (E-group) were injected with two doses of pilot produced 20 µg HP-HB vaccine. Animals in the control group (C-Group) were immunized with three doses of 10 µg Temrevac-HB. Both vaccines were administered at an interval of 3 weeks for monkeys.

CONCLUSIONS

The 2-dose regimen of the HP-HB vaccine has comparable HBV immune responses as the 3-dose regimen of Temrevac-HB vaccine in Cynomolgus monkeys.