ABSTRACT Identification of relevant epitopes is crucial for the development of subunit peptide vaccines inducing neutralizing and cellular immunity against SARS-CoV-2. Our aim was the characterization of epitopes in the receptor-binding domain (RBD) of SARS-CoV-2 spike (S) protein to generate a peptide vaccine. Epitope mapping using a panel of 10 amino acid overlapped 15-mer peptides covering region 401-515 from RBD did not identify linear epitopes when tested with sera from infected individuals or from RBD-immunized mice. However, immunization of mice with these 15-mer peptides identified four peptides located at region 446-480 that induced antibodies recognizing the peptides and RBD/S1 proteins. Immunization with peptide 446-480 from S protein formulated with Freund’s adjuvant or with CpG oligodeoxinucleotide/Alum induced polyepitopic antibody responses in BALB/c and C56BL/6J mice, recognizing RBD (titres of 3 × 10 4 –3 × 10 5 , depending on the adjuvant) and displaying neutralizing capacity (80–95% inhibition capacity; p < 0.05) against SARS-CoV-2. Murine CD4 and CD8T-cell epitopes were identified in region 446-480 and vaccination experiments using HLA transgenic mice suggested the presence of multiple human T-cell epitopes. Antibodies induced by peptide 446-480 showed broad recognition of S proteins and S-derived peptides belonging to SARS-CoV-2 variants of concern. Importantly, vaccination with peptide 446-480 or with a cyclic version of peptide 446-488 containing a disulphide bridge between cysteines 480 and 488, protected humanized K18-hACE2 mice from a lethal dose of SARS-CoV-2 (62.5 and 75% of protection; p < 0.01 and p < 0.001, respectively). This region could be the basis for a peptide vaccine or other vaccine platforms against Covid-19.
【저자키워드】 SARS-CoV-2, Neutralizing antibodies, peptide vaccine, B-cell epitopes, T-cell epitopes, 【초록키워드】 Vaccine, vaccination, S protein, antibody, Antibody Response, SARS-CoV-2 variant, peptide, Proteins, CD4, immunization, hACE2, Protein, Epitopes, Receptor-binding domain, SARS-CoV-2 variants, cellular immunity, mice, RBD, sera, peptides, K18-hACE2 mice, Neutralizing, adjuvant, neutralizing capacity, HLA, experiment, vaccine platform, epitope mapping, epitope, CpG, SARS-CoV-2 spike, Amino acid, dose, alum, identification, cysteine, characterization, lethal dose, Freund’s adjuvant, cysteines, subunit, titres, infected individual, infected individuals, S proteins, transgenic mice, linear epitopes, Freund’s, BALB/c, humanized, linear epitope, tested, identify, generate, suggested, the receptor-binding domain, recognizing, displaying, overlapped, 【제목키워드】 Vaccine, CD4, CD8, response, Neutralizing, cellular, humoral, cross-reactive, Preclinical,