Probing the Problem of Protein Vaccine Instability

Abstract

We hypothesized that vaccine stability could be improved by identifying conditions under which the native state of a protein was stabilized by strong adherence to the aluminum hydroxide adjuvant (Alhydrogel®). Using several biophysical methods, we examined the effects of Alhydrogel® in different buffer conditions on the structure and stability of recombinant protective antigen (rPA) of B. anthracis, a ricin A-chain vaccine, and staphylococcal nuclease (SNase). The secondary structures of the proteins were not significantly perturbed by Alhydrogel®. All three proteins were more resistant to thermal denaturation in succinate versus PBS buffer, in the presence of Alhydrogel®. These results are indicative of a model in which thermal stress on the proteins bound to Alhydrogel® in succinate buffer results in tighter binding and limited conformational changes, without extensive denaturation. The results indicate the "cold chain" problem of vaccine instability, or periods of heating, may be alleviated by appropriate choice of formulation conditions.