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The study focuses on the development of vaccines that do not require cold-chain storage/distribution and are suitable for needle-free delivery. Pulmonary administration is identified as one of the most promising non-parenteral routes for vaccine delivery.
The researchers engineered highly respirable dry-powder vaccine particles containing a three-fold repeated peptide epitope derived from human papillomavirus (HPV16) minor capsid protein L2 displayed on Pyrococcus furious thioredoxin as an antigen. A key feature of the engineering approach was the use of the amphiphilic endotoxin derivative glucopyranosyl lipid A (GLA) as both a coating agent enhancing particle de-aggregation and respirability as well as a built-in immune-adjuvant.
The aerodynamic performance of the vaccine was extensively characterized in vitro, and lung deposition was verified in vivo by intratracheal administration in mice of a vaccine powder containing a fluorescently labeled derivative of the antigen. This was followed by a short-term immunization study that highlighted the ability of the GLA-adjuvanted vaccine powder to induce an anti-L2 systemic immune response comparable to (or even better than) that of the subcutaneously administered liquid-form vaccine.
Despite the very short-term immunization conditions employed for this preliminary vaccination experiment, the intratracheally administered dry-powder, but not the subcutaneously injected liquid-state, vaccine induced consistent HPV neutralizing responses. Overall, the present data provide proof-of-concept validation of a new formulation design to produce a dry-powder vaccine that may be easily transferred to other antigens.
