Immunogenicity of a new type of yeast-derived hepatitis B vaccine consisting of M (pre-S2 + S) protein particles

Humoral response and genetic stability of recombinant BCG expressing hepatitis B surface antigens

The Bacille Calmette Guerin (BCG), long valued for its role as a live vaccine for the prevention of tuberculosis, is being used as a recombinant delivery vehicle for foreign antigens, principally, for inducing long-lived specific humoral and cellular immunity. Hepatitis B and its sequelae are major public health problems. Although vaccines have been available for over 20 years the disease remains a significant global problem. Many factors contribute to vaccine failure to control hepatitis B, including attaining of adequate immune protection. In this study, a novel rBCG delivery system is described using non-integrative plasmids harboring hepatitis B surface antigen genes. This rBCG was able to elicit an anti-HBs response in BALB/c mice. The titres of anti-HBs response obtained using rBCG was relatively lower than that of the commercial vaccine used as positive control. In vivo or in vitro stability assays showed that the vector used to generate rBCG is stable in spite of being a non-integrative plasmid. In addition, the HBsAg proteins expression profiles were almost similar to those obtained using an Escherichia coli expression system.

Vaccines for prevention of viral hepatitis

At the end of the 20th century active immunization against hepatitis A and B has been introduced into routine medical practice. Therefore, patients at risk, and especially those with coagulation disorders, should be immunized at the earliest age possible. In contrast, development of an efficacious vaccine against hepatitis C remains an important goal for the next decade.

Characterization of two differently glycosylated molecular species of yeast-derived hepatitis B vaccine carrying the pre-S2 region

Modified hepatitis B virus surface antigen M protein particles (HBsAg M-P31c) produced in yeast is mainly composed of two differently glycosylated proteins, GP37 and GP34. GP37 has an N-linked sugar chain and O-linked sugar chains; and GP34 has an N-linked sugar chain bound to the peptide backbone P31. Although M-P31c vaccine elicits both anti-S and anti-pre-S2 antibodies, whether there are any differences between GP37 and GP34 in the ability to elicit these antibodies is still unknown. To clarify this issue, we prepared particles which were composed solely of GP37 or GP34 by affinity chromatography, using polymerized human serum albumin as a ligand and digestion with alpha-mannosidase. We also prepared particles composed solely of P31 by successive digestion with alpha-manosidase and endo-beta-N-acetylglycosaminidase H. The vaccines derived from these three kinds of particles elicited both anti-S and anti-pre-S2 antibodies in mice to the same extent as the original M-P31c vaccine. These results suggest that the N- and O-linked sugar chains of M-P31c component proteins produced in the host yeast cells have no effect on the ability to elicit anti-S and anti-pre-S2 antibodies and that there are no differences with respect to antibody response in mice between the two major components of M-P31c, GP37 and GP34.

Detection of antibody to the PreS2 sequence of the hepatitis B virus envelope protein using an immuno-ligand assay with a silicon sensor detection system

Sensitive immunoassays are essential for establishing the efficacy of recombinant vaccines to hepatitis B virus (HBV). These experimental vaccines include the PreS2 and S domains of the HBV envelope protein. To facilitate measurement of antibody against HBV PreS2, we employed the immuno-ligand assay with silicon sensor-based detection. Labeling of immune reagents with the haptens biotin and fluorescein allows adaptation to the immunofiltration light addressable potentiometric sensor (LAPS) system. A biotinylated monoclonal anti-PreS2 antibody and anti-PreS2 in clinical serum samples competitively bind in liquid phase to a fluorescein labeled PreS2 + S antigen. Streptavidin mediates the immobilization on biotinylated nitrocellulose membranes. Fluorescein mediates binding of an anti-fluorescein urease conjugate to the immune complex. Urease serves as the signal-generating component which subsequently is measured in the LAPS reader. In comparison to a competitive RIA, the immuno-ligand assay demonstrated a four-fold improved sensitivity using a smaller sample volume. The higher sensitivity resulted in earlier detection of seroconversion during a clinical vaccine study.

Protective efficacy of a novel hepatitis B vaccine consisting of M (pre-S2 + S) protein particles (a third generation vaccine)

The protective efficacy of a new type of yeast-derived hepatitis B (HB) vaccine (TGP-943, subtype adr), which was formulated from modified M (pre-S2 + S; P31) protein (M-P31c) particles, was investigated in chimpanzees. Animals were injected intramuscularly three times at 4-week intervals with doses of 10 or 40 micrograms (as a protein) of TGP-943. There were no significant differences in the immunogenicity of 10 micrograms compared to that of 40 micrograms of TGP-943 in terms of anti-S antibody response, while the induction and persistence of anti-pre-S2 antibodies seemed dose-related. Chimpanzees, vaccinated with 40 micrograms of TGP-943, produced anti-pre-S2 antibodies 2 weeks after the first injection, which appeared earlier than anti-HBs (S) antibodies. A maximum level of the anti-pre-S2 antibodies was reached 2 weeks after the second injection. Apart from immunization with TGP-943, chimpanzees injected with denatured TGP-943, consisting of 10 micrograms (as a protein) of non-particulate M-P31c antigen, produced anti-pre-S2 antibodies with a non-protecting level of anti-S antibodies (less than 10 mIU ml-1). Five weeks after the third injection, all animals were challenged intravenously with 1000 chimpanzee infectious units of HBV subtype (ayw) and were protected as confirmed by normal serological markers, no signs of infection in the sera and liver biopsies, and no detection of HBV-DNA by PCR method. No side effects from inoculation with TGP-943 or denatured TGP-943 were also encountered in any animals.