The thermostability of a Vaccine Delivery system X-Protein (VADEX-Pro) based protein nanoparticle

Abstract

We have adapted split GFP technology into the already established VADEX-based protein nanoparticle (PNP) platform. To evaluate this new platform, a model protein, maltose binding protein (MBP), was fused to the β-strand 11 of sfGFP and co-expressed with VADEX-10 that is composed of LYRRLE peptide and N-terminal part of sfGFP. When these two fusion proteins were expressed in a cell, they were assembled into PNP spontaneously with a DLS particle size of 26 nm. The thermostability of this PNP was verified by both SDS-PAGE and DLS analysis following thermal treatment. This PNP was stable at room temperature and at temperatures as high as 40 °C for at least two months. Mutations that replaced cysteine residue of the LYRRLE peptide with serine or alanine destabilized and induced degradation of the VADEX-based PNP. The results in this study showed that the non-covalent complementation of split sfGFP became irreversible when reconstituted sfGFP was assembled in a VADEX-based PNP. This platform may be applied in developing thermostable vaccines.