| Using recombinant DNA technology, the ability to consistently produce large quantities of a vaccine antigen lacking the risks associated with live or attenuated organisms is quite attractive. Due to the dynamic and complex structure of proteins, however, such antigens are often inherently unstable. Historically, an excipient, such as sucrose, is added to the formulation, and the long-term stability is monitored using calorimetry, HPLC and/or size exclusion chromatography. While this approach can be useful, it does not provide comprehensive information regarding the conformational stability of the protein nor does it guarantee stabilization.; To improve the overall efficiency of preformulation, a systematic, three-step approach was developed. The method first uses high-throughput spectroscopic techniques to evaluate the stability of the recombinant protein antigen versus temperature and pH. 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 spectroscopic assays are employed to screen a variety of compounds for their abilities to stabilize the antigen. Finally, the ability of the protein antigen to adsorb to aluminum salt adjuvants is evaluated. This approach was applied to the preformulation development of vaccine candidates for malaria, anthrax and ricin toxicity. Such a comprehensive approach should facilitate the rapid creation of vaccines capable of maintaining activity when the cold chain may not be available and under long-term stockpile conditions. By saving time and money during the development process, the cost of vaccines may also be reduced.; Aluminum salts are currently the only FDA-approved class of vaccine adjuvants. Although they have been used in human vaccines for decades, the mechanism by which they generate an immune response is not well established. Calorimetric and spectroscopic techniques revealed that adsorbed proteins are destabilized. Additional studies suggested that stabilizers of the adsorbed antigen can be accurately predicted from the solution stability of the protein; however, the extent to which the compound affects the stability may vary. Based on this destabilization, a new mode of action for these adjuvants was proposed. By understanding how aluminum salt adjuvants work, the development of new vaccine adjuvants should be advanced. |
