Purification and functional characterization of gag-spike virus-like particles: Process optimization for efficient vaccine production

Virus-like particles (VLPs) displaying the SARS-CoV-2 Spike protein represent a promising vaccine platform due to their safety and immunogenicity. This study focuses on developing a scalable downstream process for the purification of Gag-Spike VLPs produced in suspension HEK293 cells. A tangential flow filtration (TFF) step was optimized by varying transmembrane pressure (TMP) and shear rates to maximize permeate flux while preserving particle integrity and functionality. Several chromatographic resins including SepFast DUO 5000, SepFast DUO 700, CaptoCore™ 700, CIMmultus QA monolith, and HiTrap Q were evaluated for their capacity to recover VLPs and reduce host cell proteins and DNA. Sequential purification approaches were assessed to improve recovery and purity, and the final product was subsequently passed through a sterile-filter to ensure sterility. The purified VLPs were analyzed using SDS-PAGE, dynamic light scattering, and flow-virometry. These analyses confirmed the removal of impurities, size homogeneity, and maintenance of Spike protein on the VLP surface. Flow-virometry demonstrated that a substantial portion of the VLP population retained functional Spike proteins capable of binding ACE2 and Spike antibodies. This work establishes a robust, scalable purification strategy for processing VLPs with preserved structural and functional properties suitable for vaccine development.