Biodegradable polyelectrolyte microcapsules: antigen delivery tools with Th17 skewing activity after pulmonary delivery

Because of their large surface area, the lungs appear an attractive route for noninvasive vaccine delivery, harboring the potential to induce local mucosal immune responses in addition to systemic immunity. To evoke adaptive immunity, Ags require the addition of adjuvants that not only enhance the strength of the immune response but also determine the type of response elicited. In this study, we evaluate the adjuvant characteristics of polyelectrolyte microcapsules (PEMs) consisting of the biopolymers dextran-sulfate and poly-l-arginine. PEMs form an entirely new class of microcapsules that are generated by the sequential adsorption of oppositely charged polymers (polyelectrolytes) onto a sacrificial colloidal template, which is subsequently dissolved leaving a hollow microcapsule surrounded by a thin shell. Following intratracheal instillation, PEMs were not only efficiently taken up by APCs but also enhanced their activation status. Pulmonary adaptive immune responses were characterized by the induction of a strongly Th17-polarized response. When compared with a mixture of soluble Ag with empty microcapsules, Ag encapsulation significantly enhanced the strength of this local mucosal response. Given their unique property to selectively generate Th17-polarized immune responses, PEMs may become of significant interest in the development of effective vaccines against fungal and bacterial species.