Inducing long lasting B cell and T cell immunity against multiple variants of SARS-CoV-2 through mutant bacteriophage Qβ – receptor binding domain conjugate

More than two years into the global pandemic, SARS-CoV-2 remains a significant threat to public health. Immunities acquired from infection or current vaccines fail to provide long term protection against subsequent infections, mainly due to their fast-waning nature and the emergence of variants of concerns (VOCs) such as Omicron. To overcome these limitations, SARS-CoV-2 Spike protein receptor binding domain (RBD)-based epitopes were investigated as conjugates with a powerful carrier, the mutant bacteriophage Qβ (mQβ). The epitope design was critical to eliciting potent antibody responses with the full length RBD being superior to peptide and glycopeptide antigens. The full length RBD with orientation-controlled conjugation with mQβ activated both humoral and cellular immune systems in vivo, inducing broad spectrum, persistent and comprehensive immune responses effective against multiple VOCs including Delta and Omicron variants, rendering it a promising vaccine candidate.