Preliminary stability studies of a β-SARS-CoV-2 virus-like particle vaccine

We aimed to study the stability of a Beta (β)-SARS-CoV-2 virus-like particle (VLP) vaccine in a series of preliminary experiments using selective stabilizing excipients. β-SARS-CoV-2 VLPs were produced and purified using established methodologies. The thermostability of VLPs was tested at 4°C and −30°C in the presence or absence of stabilizers polysorbate 80, sorbitol, or L-histidine in the presence of a physiological NaCl concentration of 137 mM. The integrity of VLPs was assessed using ELISA, Western immunoblot, and dynamic light scatter (DLS). β-SARS-CoV-2 VLPs were stable at 4°C for 14 days, and the addition of stabilizing excipients improved stability compared to VLPs in PBS alone. Storage of VLPs at −80°C maintained particle integrity by DLS analysis for up to 2 years. Excipients helped to maintain the antigenicity of the VLPs by ELISA and Western immunoblot, and DLS analysis revealed that VLPs retained their particulate structure. IMPORTANCE SARS-CoV-2 continues to circulate globally and cause significant illness. The problem of waning immunity to mRNA/LNPs has necessitated frequent boosters to keep pace with emerging variants. The development of alternative vaccines, therefore, remains a priority. Protein- based vaccines, like VLPs, offer a safe alternative able to produce longer-lasting immune responses. In this preliminary stability analysis, the β-SARS-CoV-2 VLPs were found to be stable at 4°C, and the addition of excipients improved VLP stability. Storage of VLPs at −30°C and −80°C also showed that the VLPs are stable for extended periods. Our findings will be of importance for the ongoing development of a SARS-CoV-2 VLP-based vaccine.