A Recombinant Protein XBB.1.5 RBD/Alum/CpG Vaccine Elicits High Neutralizing Antibody Titers against Omicron Subvariants of SARS-CoV-2

• DOI: 10.20944/preprints202309.0139.v4
• Publication Date: 2023-10-01T08:00:07Z
• Authors: Syamala Rani Thim...; Rakesh Adhikari; Maria J Villar; Jungsoon Lee; Zhuyun Liu; Rakhi Kundu; Yi-Lin Chen; Suman Sharma; Karm Ghei; Brian Keegan; Leroy Versteeg; Portia M Gillespie; Allan Ciciriello; Nelufa Yesmin; Cristina Poveda; Nestor Uzcategui; Wen-Hsiang Chen; Jason T Kimata; Bin Zhan; Ulrich Strych; Maria Elena Bottazzi; Peter Hotez; Jeroen Pollet
• Keywords: Alum; Antibody titer; CpG Oligodeoxynucleotide; CpG site

(1) Background: We previously reported the development of a recombinant protein SARS-CoV-2 vaccine, consisting Receptor-Binding Domain (RBD) spike protein, adjuvanted with aluminum hydroxide (alum) and CpG oligonucleotides. In mice non-human primates, our wild-type (WT) RBD vaccine induced high neutralizing antibody titers against WT isolate virus, and, partners in India Indonesia it was later developed into two closely resembling human vaccines, Corbevax Indovac. Here, we describe characterization next-generation adapted to recently emerging XBB variants SARS-CoV-2. (2) Methods: conducted preclinical studies using novel yeast-produced XBB.1.5 subunit candidate formulated alum CpG. examined neutralization profile sera obtained from vaccinated twice intramuscularly at 21-day interval XBB.1.5-based WT, Beta, Delta, BA.4, BQ.1.1, BA.2.75.2, XBB.1.16, EG.5.1 pseudoviruses. (3) Results: The RBD/CpG/alum elicited robust response mice. Furthermore, serum demonstrated potent pseudovirus as well several other Omicron However, regardless cross-reactivity by ELISA, anti-XBB.1.5 antigen showed low Delta virus variants. (4) Conclusions: Whereas observed modest cross-neutralization subvariants RBD/CpG/Alum or BA.4/5-based raised cross-neutralization. These findings underscore imminent opportunity for an updated formulation utilizing antigen.