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
Jeroen Pollet, Wen‐Hsiang Chen, Leroy Versteeg, Brian Keegan, Bin Zhan, Junfei Wei, Zhuyun Liu, Jungsoon Lee, Rahki Kundu, Rakesh Adhikari, Cristina Poveda, María José Villar, Ana Carolina de Araújo Leão, Joanne Altieri Rivera, Zoha Momin, Portia M. Gillespie, Jason T. Kimata, Ulrich Strych, Peter J. Hotez, María Elena Bottazzi
Abstract
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.