Formulation of dry powders of vaccines containing MF59 or AddaVax by thin-film freeze-drying

Oil-in-water (O/W) nanoemulsion-based vaccine adjuvants such as MF59 are often used in seasonal and pandemic influenza vaccines. However, vaccines containing nanoemulsions require cold chain for storage and are sensitive to accidental freezing. We explored the feasibility of developing dry powders of vaccines adjuvanted with MF59 or AddaVaxÔ, a preclinical grade nanoemulsion that has the same composition and droplet size as MF59, by thin-film freeze-drying (TFFD). AddaVax alone was successfully converted from a liquid to dry powders by TFFD using trehalose as a stabilizing agent while maintaining the droplet size distribution of the AddaVax when reconstituted, whereas subjecting the same AddaVax composition to conventional shelf freeze-drying led to significant aggregation or fusion. TFFD was then applied to convert liquid AddaVax-adjuvanted vaccines containing either model antigens such as ovalbumin and lysozyme, mono-, bi-, and tri-valent recombinant hemagglutinin (rHA) protein-based H1 and/or H3 (universal) influenza vaccine candidates, as well as the MF59-containing Fluad Quadrivalent influenza vaccine to dry powders. Antigens, stabilizing agents, and buffer showed different effects on the physical properties of the vaccines (e.g., mean particle size and particle size distribution) after subjected to TFFD, but the integrity and hemagglutination activity of the rHA antigens did not significantly change and the immunogenicity of reconstituted influenza vaccine candidates was preserved when evaluated in BALB/c mice. The vaccine dry powder was not sensititve to repeated freezing-and-thawing, in contrast to its liquid counterpart. It is concluded that TFFD can be applied to convert vaccines containing MF59 or an nanoemulsion with the same composition and droplet size as MF59 from liquid to dry powders while maintaining the immunogencity of the vaccines, and it may be used to prepare dry powders of multivalent universal influenza vaccines.