Tehran University Medical Journal (May 2007)
Comparison of immunogenicity of Aluminum salts as adjuvant for recombinant Hepatitis-B vaccine
Abstract
Background: Aluminum salts are common adjuvants in human and animal vaccine preparations. The two adjuvants aluminum phosphate and aluminum hydroxide show acceptable immunoadjuvant properties with many antigens. These two salts have different physicochemical characteristics that make each one suitable for certain antigens. The surface antigen of Hepatitis B (HBsAg) has several antigenic epitopes that bind to aluminum adjuvants by a ligand exchange mechanism. Although HBV vaccines using an aluminum hydroxide adjuvant are available, higher antigenicity is needed for the subgroup of people who do not respond sufficiently to the currently available vaccines. Methods: A solution of recombinant HBsAg for making different formulations of vaccines with aluminum phosphate (Adju-Phos®) and aluminum hydroxide (Alhydrogel®) adjuvants was obtained from Darupakhsh Pharmaceutical Company. The total protein content, antigenicity, and purity of HBsAg solution were determined using BCA, ELISA, and SDS-PAGE methods, respectively. The different formulations were prepared in the lab and administered i.p. to two test groups of Balb/C mice and a third test group received the Engerix vaccine, which is currently available on the market and uses an aluminum hydroxide adjuvant. The control group of animals received the solution without antigen. After 28 days, heart blood samples were collected and serum was separated to determine the antibody titer against HBsAg using an ELISA kit. Results: This study shows that the vaccine formulated with aluminum phosphate exerted more immunogenicity than both the aluminum hydroxide laboratory formulation and the Engerix vaccines. Conclusion: Although the results of our study indicate higher immunogenic properties of the vaccine formulated with the aluminum phosphate adjuvant, complementary experiments are needed to further evaluate the biological properties with respect to effectiveness, adverse effects, product stability and finally possibility for manufacturing and distribution of this new formulation as a Hepatitis B vaccine.
