Adsorption of recombinant poxvirus L1-protein to aluminum hydroxide/CpG vaccine adjuvants enhances immune responses and protection of mice from vaccinia virus challenge

Abstract

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.

Effect of Aluminum Adjuvant and Preservatives on Structural Integrity and Physicochemical Stability Profiles of Three Recombinant Subunit Rotavirus Vaccine Antigens

“…although that has more recently been shown to be antigen specific. Studies with poxvirus L1-protein antigen in our laboratories demonstrated AH binding is important for immunopotentiation, 26 and others have reported similar observations with pneumococcal protein antigens. 27 The WHO recommends greater than 80% of the diphtheria and tetanus toxoids to be adsorbed to aluminum adjuvants.…”

TLR3 and TLR9 Agonists Improve Postexposure Vaccination Efficacy of Live Smallpox Vaccines

“…These facts led us to examine the effect on the immune response by activating two TLRs; TLR3 and TLR9 using their synthetic agonists (synthetic double stranded RNA molecules and bacterial CpG DNA, respectively). While adjuvants are routinely added to inactivated or subunit vaccines to confer pre-exposure immunity [32] , [45] – [47] , in the present study we co-administered the adjuvant with a live vaccine and examined it as a therapeutic/p.e. treatment.…”

Synthetic Nanoparticles for Vaccines and Immunotherapy

“…110 For example, for a recombinant smallpox L1-protein subunit vaccine, binding of antigen to alum particles was required for optimal immune responses. 111 Phosphate buffer treatment, which changed the surface charge of the aluminum particulates from positive to negative prior to vaccination, disrupted protein binding and reduced serum IgG titers, leading to increased morbidity and weight loss (an indirect measure of disease state) upon vaccinia virus challenge.…”