A rapid, three-step process for the preformulation of a recombinant ricin toxin A-chain vaccine

A systematic, three-step approach was employed to develop a stable, optimized formulation of ricin toxin A-chain V76M/Y80A (rRTA) for use as a vaccine against ricin toxicity. The method first uses spectroscopic techniques to evaluate the stability of rRTA as a function of temperature and pH. To synthesize the data, empirical phase diagrams are generated to display the conditions under which the protein maintains particular conformational states. Following identification of optimal pH conditions, light scattering and fluorescence assays are employed to screen a wide variety of compounds for their abilities to stabilize rRTA. Once stabilizers were identified, the ability of rRTA to adsorb to aluminum salt adjuvants was evaluated. Desorption of the protein from the adjuvant was also analyzed. Using this approach, the optimal formulation conditions for rRTA were determined to be pH 6.0 utilizing glycerol as a stabilizer and Alhydrogel as an adjuvant. Such an approach has the potential to significantly reduce the time it takes to get vaccines into clinical testing.