The stockpiling of live vaccinia virus
vaccines has enhanced biopreparedness against the intentional or accidental release of
smallpox. Ongoing research on future generation
smallpox vaccines is providing key insights into protective immune responses as well as important information about
subunit-vaccine design strategies. For
protein-based recombinant
subunit vaccines, the formulation and stability of candidate
antigens with different adjuvants are important factors to consider for
vaccine design. In this work, a non-tagged secreted L1-protein, a target
antigen on mature virus, was expressed using recombinant baculovirus technology and purified. To identify optimal formulation conditions for L1, a series of biophysical studies was performed over a range of pH and temperature conditions. The overall physical stability profile was summarized in an empirical phase diagram. Another critical question to address for development of an adjuvanted
vaccine was if immunogenicity and protection could be affected by the interactions and binding of L1 to
aluminum salts (
Alhydrogel) with and without a second adjuvant, CpG. We thus designed a series of
vaccine formulations with different binding interactions between the L1 and the two adjuvants, and then performed a series of vaccination-challenge experiments in mice including measurement of antibody responses and post-challenge
weight loss and survival. We found that better humoral responses and protection were conferred with
vaccine formulations when the L1-protein was adsorbed to
Alhydrogel. These data demonstrate that designing
vaccine formulation conditions to maximize
antigen-adjuvant interactions is a key factor in
smallpox subunit-vaccine immunogenicity and protection.