Spray dried VSV-vectored vaccine is thermally stable and immunologically active in vivo.

Effective vaccine delivery and coverage to rural and resource-poor countries is hindered by the dependence on cold chain storage. As such, developments of cold chain-free technologies are highly sought. Although spray dried adenoviral vectors have shown long term stability at ambient temperatures and relatively low humidity, it remains to be determined whether similar excipient formulations are applicable to other viral vectors. To address this, we have spray dried vesicular stomatitis virus (VSV)-vectors with a panel of well-characterized sugar excipients to determine the optimal formulation for vector stabilization. Upon reconstitution, we show that trehalose conferred superior stability of VSV both in vitro and in vivo. Importantly, following cold chain-free storage at elevated temperatures at 37 °C for 15 days, we show that a VSV-vectored vaccine retains its in vivo immunogenicity, whereas a liquid control completely lost its immune-stimulating ability. Our results provide foundational evidence that spray drying with properly tested excipients can stabilize viral vectors such as VSV, allowing them to be stored long-term at elevated temperatures without dependency on cold chain conditions.

Excipient selection for thermally stable enveloped and non-enveloped viral vaccine platforms in dry powders.

Two enveloped viral vectors, vesicular stomatitis virus and influenza virus, and a non-enveloped viral vector, human adenovirus type 5, were encapsulated by spray drying to enhance thermal stability.Results with these candidates led to the hypothesis that stability performance of chosen excipients may be less virus-specific, as previously postulated in the literature, and more differentiated based on whether the virus has a lipid envelope. Spray dried samples were characterized for their thermal properties, RNA viability and in vitro viral activity after storage at 37 °C for up to 30 days or at 45 °C for up to 3 days. The enveloped viral vectors, as a group, were more thermally stable in trehalose while the non-enveloped viral vector showed higher activity with mannitol as the primary excipient in blends. Trehalose shows strong hydrogen bonds with the envelope's lipid membrane than the other carbohydrates, more effectively replacing water molecules while maintaining the fluidity of the membrane. Conversely, the small size of mannitol molecules was attributed to the more effective hydrogen bonding between water and the protein capsid of non-enveloped viral vectors. In all cases, a matrix with high glass transition temperature contributed to thermal stabilization through vitrification. This work suggests that carbohydrate stabilizer selection may be more dependent on the envelope rather than the specific viral vector, which, if universally true, will provide a guideline for future formulation development.

Spray dried human and chimpanzee adenoviral-vectored vaccines are thermally stable and immunogenic in vivo.

Cold chain-free vaccine technologies are needed to ensure effective vaccine delivery and coverage, particularly in resource-poor countries. However, the immunogenicity and thermostability of spray dried live viral vector-based vaccines such as recombinant adenoviral-vectored vaccines remain to be investigated. To address this issue, we have spray dried human adenoviral (AdHu5)- and chimpanzee adenoviral (AdCh68)-vectored tuberculosis vaccines in a mannitol and dextran matrix. Spray dried powders containing these two vaccines display the morphologic and chemical properties desired for long-term thermostability and vaccination. Upon reconstitution, they effectively transfected the cells in vitro with relatively small losses in viral infectivity related to the spray drying process. Following in vivo vaccination, AdHu5- and AdCh68-vectored vaccines were as immunogenic as the conventional fresh, cryopreserved liquid vaccine samples. Of importance, even after cold chain-free storage, at ambient temperatures and relatively low humidity for 30 and 90days, the vaccines retained their in vivo immunogenicity, while the liquid vaccine samples stored under the same conditions lost their immune-activating capability almost entirely. Our results support further development of our spray drying technologies for generating thermally stable adenoviral-vectored and other viral-vectored vaccines.