(156d) An Investigation of the Pulmonary and Systemic Persistence of Polyanhydride Nanoparticle Vaccine Formulations

Polyanhydrides have properties that make them ideal candidates for vaccine delivery including the ability to stabilize and protect fragile protein antigens, provide a sustained release of antigen, and modulate the immune response. Homopolymers and copolymers based on sebacic acid (SA), 1,6-bis-(p-carboxyphenoxy)hexane (CPH) and 1,8-bis-(p-carboxyphenoxy)-3,6-dioxaoctane (CPTEG) have shown efficacy in vaccine formulations. Encapsulation of F1-V protein (an antigen of Yersinia pestis) into nanoparticles made from CPTEG:CPH copolymers demonstrated the ability to provide protection against a lethal bacterial challenge. Additionally, polyanhydride nanoparticles made from CPH:SA copolymers have been shown to preserve the functionality of the protective antigen (PA) of Bacillus anthracis when stored at 37°C for up to one year.

In this work, we have integrated live animal imaging, confocal microscopy, and flow cytometry to analyze the deposition, uptake, and in vivo persistence of PA delivered via the polyanhydride nanoparticle platform over 12 weeks.  Distribution and uptake of antigen-loaded polyanhydride nanoparticles administered intranasally is different than traditional adjuvants such as MPLA, reaching the deep recesses of the lungs, where they are internalized and persist for more than 42 days.  Our previous work has demonstrated that protective polyanhydride vaccine formulations contain a combination of both soluble and encapsulated antigen by providing an immediate immune response stimulus followed by sustained antigen release to generate affinity matured antibodies and long-lasting immunity. This current study supports these observations, demonstrating the differential in vivo distribution kinetics of soluble versus nanoparticle encapsulated PA antigen through ex vivo organ imaging of fluorescently tagged PA. These studies lay the foundation for mechanistic insight into continued antigen persistence in the immunization site leading to high antibody titer with increased avidity.