A novel therapeutic hepatitis B vaccine induces cellular and humoral immune responses and breaks tolerance in hepatitis B virus (HBV) transgenic mice.

Therapeutic vaccines are currently being developed for chronic hepatitis B and C. As an alternative to long-term antiviral treatment or to support only partially effective therapy, they should activate the patient's immune system effectively to fight and finally control the virus. A paradigm of therapeutic vaccination is the potent induction of T-cell responses against key viral antigens - besides activation of a humoral immune response. We have evaluated the potential of a novel vaccine formulation comprising particulate hepatitis B surface (HBsAg) and core antigen (HBcAg), and the saponin-based ISCOMATRIX™ adjuvant for its ability to stimulate T and B cell responses in C57BL/6 mice and its ability to break tolerance in syngeneic HBV transgenic (HBVtg) mice. In C57BL/6 mice, the vaccine induced multifunctional HBsAg- and HBcAg-specific CD8+ T cells detected by staining for IFNγ, TNFα and IL-2, as well as high antibody titers against both antigens. Vaccination of HBVtg animals induced potent HBsAg- and HBcAg-specific CD8+ T-cell responses in spleens and HBcAg-specific CD8+ T-cell responses in livers as well as anti-HBs seroconversion two weeks post injection. Vaccination further reduced HBcAg expression in livers of HBVtg mice without causing liver damage. In summary, this study demonstrates therapeutic efficacy of a novel vaccine formulation in a mouse model of immunotolerant, chronic HBV infection.

A controlled clinical trial comparing the safety and immunogenicity of a new adjuvanted hepatitis B vaccine with a standard hepatitis B vaccine.

A randomised trial was conducted in 285 adults not immune to hepatitis B (HB) to compare the safety and immunogenicity of a commercial aluminium-adjuvanted HB vaccine with and without an additional new adjuvant (AgB/RC-210-04 or AgB study groups, respectively). The additional adjuvant RC-529 is a fully synthetic monosaccharide mimetic of monophosphoryl lipid A. Subjects in the AgB/RC-210-04 (n=136) and AgB (n=149) groups were vaccinated intramuscularly on days 0, 30, and 180, according to the standard vaccination schedule for hepatitis B vaccines. Serum levels of anti-HBs were measured on days 30, 60, 90, 180, and 210. Standard safety assessments were made throughout the study period. The rates of seroprotection (anti-HBs > or =10.0 mIU/ml) were significantly greater for the AgB/RC-210-04 group at all time points: at day 90, the seroprotection rate, the primary endpoint of the trial, was 99% for AgB/RC-210-04 compared with 84% for AgB (p<0.0001). Similarly, geometric mean anti-HBs titres were significantly higher at all time points for the AgB/RC-210-04 group. There were more local reactions in the AgB/RC-210-04 group, however they were transient and this double-adjuvanted formulation was well tolerated. We conclude that the addition of a synthetic adjuvant to the AgB vaccine significantly enhanced the immunogenicity of the commercial vaccine AgB. The results indicate furthermore that a two-dose regime of the double-adjuvanted vaccine (schedule: 0-1 month) may be sufficient to achieve seroprotection in nearly 100% of individuals.

Intranasal immunization with recombinant antigens associated with new cationic particles induces strong mucosal as well as systemic antibody and CTL responses.

New cationic nanoparticles (SMBV) were evaluated for use as a nasal vaccine delivery system for two recombinant proteins: HBsAg and beta-galactosidase. Each protein was formulated with SMBV and intranasally administrated to non-anesthetized mice. In each model, the formulated protein induced high levels of specific serum IgG antibodies and cytotoxic T lymphocyte (CTL) responses. Moreover, specific IgA antibodies were found in nasal as well as in vaginal washes of intranasally immunized mice with the protein associated with SMBV. In contrast, no IgG or IgA antibodies and no CTL were detected in mice immunized with free protein. The detection of a CTL response and an increase in both IgG1 and IgG2a antibodies in serum suggest that SMBV amplifies both Th1 and Th2 responses without modifying the Th1/Th2 profile of the immune response induced by the natural protein. These data demonstrate the high potential of SMBV for use as a nasal delivery system for sub-unit vaccines.

Comparative efficacy, safety and immunogenicity of Hepavax-Gene and Engerix-B, recombinant hepatitis B vaccines, in infants born to HBsAg and HBeAg positive mothers in Vietnam: an assessment at 2 years.

In a randomized, controlled trial, 105 healthy full-term infants born to HBsAg and HBeAg positive mothers received three doses (at 0, 1 and 6 months) of either a new recombinant hepatitis B vaccine (Hepavax-Gene) or Engerix-B. Both groups were also given hepatitis B specific Hepa-big immunoglobulin (HBIG) within 24h of birth. Levels of antibodies to hepatitis B surface antigen (anti-HBs) were assessed on days 30, 60, 210, 360, and 2 years post-vaccination. Efficacy and immunogenicity and safety of the two vaccines were not significantly different; both vaccines achieved >94% seroprotection within 360 days. At 2 years, only one subject (1.9%) in the Hepavax-Gene group and two subjects (3.9%) in the Engerix-B group were HBsAg positive. No serious adverse events (AEs) were observed in either group.