Cutting edge: mucosal application of a lyophilized viral vector vaccine confers systemic and protective immunity toward intracellular pathogens.

A major problem of current vaccines is storage stability, often requiring strict maintenance of cold chains. In the course of the eradication of smallpox, a freeze-dried vaccinia virus (Dryvax), which proved to be very stable, was used to overcome this limitation. However, Dryvax needs to be reconstituted before usage and is administered using a bifurcated needle, procedures that pose a number of additional health risks. We report in this study that a stable, lyophilized, modified vaccinia virus Ankara (MVA) vaccine can be directly applied to the nostrils of mice without previous reconstitution. This direct mucosal application induced systemic Ab and T cell responses comparable to those achieved by i.m. administration. Importantly, mucosal application of lyophilized MVA induced long-lasting protective immunity against lethal bacterial and viral challenges. These data clearly demonstrate the potency of a simple needle-free vaccination, combining the advantages of mucosal application with the stability and efficiency of lyophilized MVA.