(489r) Effect of Plasma Protein Adsorption in the in Vitro Activation of Murine Dendritic Cells by Polyanhydride Microparticles

In order to overcome the poor immunogenicity of recombinant proteins used for vaccination, researches have focused on the development of new vaccine adjuvants. Polyanhydride microparticles have shown immunomodulatory properties that, when combined with their ability to stabilize and provide sustained and slow release of antigens, make them excellent candidates as adjuvants for the design of single dose vaccines. A special characteristic of this class of polymer carriers is that their adjuvant effect can be tailored by controlling polyanhydride chemistry. It has been suggested that the biodistribution and biocompatibility of antigen carriers, and therefore their effectiveness as vaccine adjuvants, can be influenced by the adsorption of serum proteins in vivo. Our previous work has shown that plasma protein adsorption patterns on polyanhydrides microparticles are correlated to their surface properties (i.e., hydrophobicity) and depend upon the specific protein being adsorbed, suggesting that the plasma adsorption can be tailored by controlling the particle surface chemistry. Activation of dendritic cells (DCs) plays a major role in inducing protective immunity and polyanhydrides particles have been shown to activate DCs. The main goal of this work is to understand the effect of plasma protein adsorption on the adjuvant properties of polyanhydride carriers. For this study, polymers based on sebacic acid (SA), 1,6-bis(p-carboxyphenoxy)hexane (CPH), and 1,8-bis(p-carboxyphenoxy)-3,6-dioxaoctane (CPTEG) anhydrides were synthesized. Cryogenic atomization was used to fabricate CPH:SA and CPTEG:CPH microspheres that were characterized by SEM. Whole mouse serum as well as specific plasma proteins (albumin, immunoglobulin G, and fibrinogen) were absorbed on the surface of polymer microparticles. 2-D SDS-PAGE electrophoresis was used to characterize protein adsorption. DCs were cultured from the bone marrow of C57BL/6 mice and incubated with the protein-adsorbed microparticles. After incubation, DCs were collected and assessed by flow cytometry for the surface expression of CD11c, MHC II, CD86, CD40, and CD209. In addition, culture supernatants were collected and analyzed for the presence of cytokines (IL-6, IL-10, IL-12p40, and TNF-alfa). Pre-adsorption of specific plasma proteins like immunoglobulin G and fibrinogen upregulates the expression of all the cell surface markers and of the cytokines, IL-6 and TNF-alfa, compared to DCs stimulated with non-adsorbed particles. This suggests that pre-adsorption of specific plasma proteins can be used as an approach to enhance particle uptake by DCs. The knowledge gained from this work can be used to effectively and rationally design new vaccines.