IgG and rF1-V Stability in the Presence of Polyanhydride Degradation Products

Biodegradable, surface-erodible polyanhydrides have been shown to stabilize and provide sustained release of proteins (e.g., ovalbumin, lysozyme). The goal of this study was to show that therapeutic proteins such as immunoglobulin G (IgG) and recombinant rF1-V are stable in the presence of polyanhydride degradation products. For this study, IgG and rF1-V were incubated separately in the presence of the degradation products of three polyanhydrides: sebacic acid (SA), 1,6-bis(p-carboxyphenoxyhexane) (CPH), and 1,8-bis(p-carboxyphenoxy)-3,6-dioxaoctane (CPTEG). After incubation for 0 and 7 days, the primary, secondary, and tertiary structure of IgG and rF1-V were evaluated using SDS-PAGE, circular dichroism, and fluorescence spectroscopy, respectively. To study the antigenicity of IgG, an ELISA assay was used while Western blot analysis was used to evaluate the stability of rF1-V. The results showed that the structure and antigenicity of IgG were not altered. The primary structure of rF1-V was altered (i.e., aggregation) when incubated with solutions containing CPH monomer. Both SA and CPH also affected the secondary structure. The antigenicity was also affected by the CPH monomer. These results suggest that rF1-V is affected by the acidity of SA and the hydrophobicity of CPH, suggesting that there are optimal copolymer compositions for stabilization. These results are promising for the rational design of new and effective vaccine adjuvants based on biodegradable polyanhydrides.