TY - JOUR T1 - SARS-CoV-2 RBD219-N1C1: A Yeast-Expressed SARS-CoV-2 Recombinant Receptor-Binding Domain Candidate Vaccine Stimulates Virus Neutralizing Antibodies and T-cell Immunity in Mice JF - bioRxiv DO - 10.1101/2020.11.04.367359 SP - 2020.11.04.367359 AU - Jeroen Pollet AU - Wen-Hsiang Chen AU - Leroy Versteeg AU - Brian Keegan AU - Bin Zhan AU - Junfei Wei AU - Zhuyun Liu AU - Jungsoon Lee AU - Rahki Kundu AU - Rakesh Adhikari AU - Cristina Poveda AU - Maria-Jose Villar Mondragon AU - Ana Carolina de Araujo Leao AU - Joanne Altieri Rivera AU - Portia M. Gillespie AU - Ulrich Strych AU - Peter J. Hotez AU - Maria Elena Bottazzi Y1 - 2020/01/01 UR - http://biorxiv.org/content/early/2020/11/05/2020.11.04.367359.abstract N2 - There is an urgent need for an accessible and low-cost COVID-19 vaccine suitable for low- and middle-income countries. Here we report on the development of a SARS-CoV-2 receptor-binding domain (RBD) protein, expressed at high levels in yeast (Pichia pastoris), as a suitable vaccine candidate against COVID-19. After introducing two modifications into the wild-type RBD gene to reduce yeast-derived hyperglycosylation and improve stability during protein expression, we show that the recombinant protein, RBD219-N1C1, is equivalent to the wild-type RBD recombinant protein (RBD219-WT) in an in vitro ACE-2 binding assay. Immunogenicity studies of RBD219-N1C1 and RBD219-WT proteins formulated with Alhydrogel® were conducted in mice, and, after two doses, both the RBD219-WT and RBD219-N1C1 vaccines induced high levels of binding IgG antibodies. Using a SARS-CoV-2 pseudovirus, we further showed that sera obtained after a two-dose immunization schedule of the vaccines were sufficient to elicit strong neutralizing antibody titers in the 1:1,000 to 1:10,000 range, for both antigens tested. The vaccines induced IFN-γ, IL-6, and IL-10 secretion, among other cytokines. Overall, these data suggest that the RBD219-N1C1 recombinant protein, produced in yeast, is suitable for further evaluation as a human COVID-19 vaccine, in particular, in an Alhydrogel® containing formulation and possibly in combination with other immunostimulants.Competing Interest StatementThe authors declare that Baylor College of Medicine recently licensed the RBD219-N1C1 technology to an Indian manufacturer for further development. The research conducted in this paper was performed in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest. ER -