Developing a Thermostable SARS-CoV-2 RBD-particle Vaccine

PROJECT SUMMARY The coronavirus disease 2019 (COVID-19) global pandemic caused by Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) is unprecedented in our lifetime and has caused major social, economic and human suffering. Globally, there have been 76,858,506 confirmed cases, leading to 1,711,498 deaths as reported by the WHO through December 2020. The rollout of FDA-authorized Pfizer (-80 ˚C storage) and Moderna (-20 ˚C storage) vaccines has highlighted the challenges posed by low requisite storage temperatures. Elimination of cold chain requirements for emerging vaccine solutions could facilitate distribution and provide considerable supply chain cost savings. To overcome cold chain requirements, POP Biotechnologies proposes to investigate a lyophilization strategy for its novel vaccine adjuvant platform that induces spontaneous antigen particles, using the receptor-binding domain (RBD) of the SARS CoV-2 spike (S) protein. We were amongst the first to show that a liquid form of RBD particles potently increases SARS-CoV-2 neutralizing antibodies by orders of magnitude compared to the soluble antigen. Our vaccine platform induces the particle formation of well- characterized his-tagged antigens by simple admixing with liposomes that contain small amounts of cobalt porphyrin-phospholipid (CoPoP) and the clinical adjuvants monophosphoryl lipid A and QS-21. CoPoP liposomes give rise to rapid antigen particleization that is stable in biological media. In this collaborative Phase I SBIR proposal, we will assess the impact of lyophilization on the conformational and thermal stability of the resulting lyophilized vaccine, evaluated by biochemical and biophysical assays, and its efficacy will be assessed by functional immunogenicity in mice. This project will assess the feasibility of breaking the cold-chain requirements for a next-generation particle vaccine system, which could be critical for resource-limited settings. In collaboration with the Texas Biomedical Research Institute (TBRI), a transgenic mouse model for SARS-CoV- 2 infection will be used to study the thermostability on protection induced by the lyophilized, RBD particle vaccine. 1