Engineered SARS-CoV-2 receptor binding domain improves immunogenicity in mice and elicits protective immunity in hamsters

Global containment of COVID-19 still requires accessible and affordable vaccines for low- and middle-income countries (LMICs).[1][1] Recently approved vaccines provide needed interventions, albeit at prices that may limit their global access.[2][2] Subunit vaccines based on recombinant proteins are suited for large-volume microbial manufacturing to yield billions of doses annually, minimizing their manufacturing costs.[3][3] These types of vaccines are well-established, proven interventions with multiple safe and efficacious commercial examples.[4][4]–[6][5] Many vaccine candidates of this type for SARS-CoV-2 rely on sequences containing the receptor-binding domain (RBD), which mediates viral entry to cells via ACE2.[7][6],[8][7] Here we report an engineered sequence variant of RBD that exhibits high-yield manufacturability, high-affinity binding to ACE2, and enhanced immunogenicity after a single dose in mice compared to the Wuhan-Hu-1 variant used in current vaccines. Antibodies raised against the engineered protein exhibited heterotypic binding to the RBD from two recently reported SARS-CoV-2 variants of concern (501Y.V1/V2). Presentation of the engineered RBD on a designed virus-like particle (VLP) also reduced weight loss in hamsters upon viral challenge. ### Competing Interest Statement L.E.C., K.R.L., and J.C.L. have filed patents related to the InSCyT system and methods. N.C.D., S.R.A., and J.C.L. have filed a patent related to the RBD-L452K-F490W sequence. K.R.L., L.E.C., and M.K.T. are current employees at Sunflower Therapeutics PBC. J.C.L. has interests in Sunflower Therapeutics PBC, Pfizer, Honeycomb Biotechnologies, OneCyte Biotechnologies, QuantumCyte, Amgen, and Repligen. J.C.L's interests are reviewed and managed under MIT's policies for potential conflicts of interest. J.M.S. is an employee of the Bill & Melinda Gates Medical Research Institute. H.K. is an employee of the Bill & Melinda Gates Foundation. [1]: #ref-1 [2]: #ref-2 [3]: #ref-3 [4]: #ref-4 [5]: #ref-6 [6]: #ref-7 [7]: #ref-8