Establishment of a soluble expression and rapid purification system for self-assembling protein nanoparticle and characterization of its physiochemical properties

Abstract

Rotavirus is the leading cause of life-threatening diarrhea in infants and young children, posing serious casualties and economic losses every year. Effective vaccines are urgently needed to combat rotavirus and protect the health of young children. In our previous study, a potential vaccine candidate was developed by using the ferritin nanocage as a platform to display the inner capsid protein VP6 of rotavirus on its surface. It could induce highly efficient humoral and mucosal immunogenicity in mice by oral administration. However, the biological macromolecule of recombinant rVP6-Ferritin was expressed as inclusion bodies in prokaryotic expression system, severely limiting its preparations, physical characterizations, and potential applications. In this work, we exploited a soluble, effective, and convenient method for the expression and purification of biological macromolecule rVP6-Ferritin. Similar to ferritin, the recombinant rVP6-Ferritin could self-assembling into spherical nanoparticles in the nanometer range with remarkable uniformity. However, the rVP6-Ferritin nanoparticles exhibited different surface morphology and pH-dependent size behavior from the ferritin nanocages. To our knowledge, this is the first report of expressing the ferritin-based antigen nanoparticles with good solubility in prokaryotic system by cell-surface display technique. Based on this work, more self-assembling biological macromolecule with nanometer scale could be rationally designed and conveniently manufactured for use in vaccines, drug delivery, gene therapy, and materials science.