{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,4,6]],"date-time":"2026-04-06T14:40:15Z","timestamp":1775486415737,"version":"3.50.1"},"reference-count":31,"publisher":"MDPI AG","issue":"6","license":[{"start":{"date-parts":[[2025,5,29]],"date-time":"2025-05-29T00:00:00Z","timestamp":1748476800000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Vaccines"],"abstract":"<jats:p>(1) Background: The COVID-19 pandemic highlights the critical necessity for the development of mucosal vaccines. (2) Objective: In this study, we aimed to develop mucosal vaccines based on the receptor-binding domain (RBD) of the SARS-CoV-2 Spike protein. (3) Methods: We engineered the RBD of the Spike protein by incorporating ten lysine residues (K10), thereby enhancing its positive charge under physiological conditions. (4) Results: Although this modification did not directly augment the immunogenicity of the antigen, its combination with the mucosal adjuvant cholera toxin B subunit (CTB) and administration via the pulmonary route in BALB\/c mice resulted in the induction of robust neutralizing antibody titers. Antigen-specific antibody responses were observed in both serum and bronchoalveolar lavage fluid. Importantly, serum IgG antibody titers remained above 104 six months following third immunization, suggesting the establishment of sustained long-term immunity. Additionally, the incorporation of five lysine residues (K5) into the RBD, in conjunction with CTB, significantly increased serum IgG and IgA antibody titers. (5) Conclusions: Adding poly-lysine to RBD and combining it with CTB can stimulate robust mucosal and humoral immune responses in mice. These findings offer valuable insights for the design of subunit mucosal vaccines.<\/jats:p>","DOI":"10.3390\/vaccines13060582","type":"journal-article","created":{"date-parts":[[2025,5,29]],"date-time":"2025-05-29T09:47:34Z","timestamp":1748512054000},"page":"582","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":1,"title":["A Poly-Lysine-Based RBD Mucosal Vaccine Induces Potent Antibody Responses in Mice"],"prefix":"10.3390","volume":"13","author":[{"given":"Huifang","family":"Xu","sequence":"first","affiliation":[{"name":"Laboratory of Advanced Biotechnology, Beijing Institute of Biotechnology, 20 Dongdajie Street, Fengtai District, Beijing 100071, China"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Han","family":"Wang","sequence":"additional","affiliation":[{"name":"Laboratory of Advanced Biotechnology, Beijing Institute of Biotechnology, 20 Dongdajie Street, Fengtai District, Beijing 100071, China"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Peng","family":"Sun","sequence":"additional","affiliation":[{"name":"Laboratory of Advanced Biotechnology, Beijing Institute of Biotechnology, 20 Dongdajie Street, Fengtai District, Beijing 100071, China"},{"name":"School of Basic Medical Sciences, Tsinghua University, No. 30 Shuangqing Road, Haidian District, Beijing 100084, China"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Tiantian","family":"Wang","sequence":"additional","affiliation":[{"name":"Laboratory of Advanced Biotechnology, Beijing Institute of Biotechnology, 20 Dongdajie Street, Fengtai District, Beijing 100071, China"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Bin","family":"Zhang","sequence":"additional","affiliation":[{"name":"Laboratory of Advanced Biotechnology, Beijing Institute of Biotechnology, 20 Dongdajie Street, Fengtai District, Beijing 100071, China"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Xuchen","family":"Hou","sequence":"additional","affiliation":[{"name":"Laboratory of Advanced Biotechnology, Beijing Institute of Biotechnology, 20 Dongdajie Street, Fengtai District, Beijing 100071, China"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Jun","family":"Wu","sequence":"additional","affiliation":[{"name":"Laboratory of Advanced Biotechnology, Beijing Institute of Biotechnology, 20 Dongdajie Street, Fengtai District, Beijing 100071, China"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-6655-1866","authenticated-orcid":false,"given":"Bo","family":"Liu","sequence":"additional","affiliation":[{"name":"Laboratory of Advanced Biotechnology, Beijing Institute of Biotechnology, 20 Dongdajie Street, Fengtai District, Beijing 100071, China"}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"1968","published-online":{"date-parts":[[2025,5,29]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"265","DOI":"10.1038\/s41586-020-2008-3","article-title":"A New Coronavirus Associated with Human Respiratory Disease in China","volume":"579","author":"Wu","year":"2020","journal-title":"Nature"},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"77","DOI":"10.1126\/science.abc1932","article-title":"Development of an Inactivated Vaccine Candidate for SARS-CoV-2","volume":"369","author":"Gao","year":"2020","journal-title":"Science"},{"key":"ref_3","doi-asserted-by":"crossref","first-page":"572","DOI":"10.1038\/s41586-020-2599-8","article-title":"A Vaccine Targeting the RBD of the S Protein of SARS-CoV-2 Induces Protective Immunity","volume":"586","author":"Yang","year":"2020","journal-title":"Nature"},{"key":"ref_4","doi-asserted-by":"crossref","first-page":"1271","DOI":"10.1016\/j.cell.2020.07.024","article-title":"A Thermostable mRNA Vaccine Against COVID-19","volume":"182","author":"Zhang","year":"2020","journal-title":"Cell"},{"key":"ref_5","doi-asserted-by":"crossref","first-page":"169","DOI":"10.1016\/j.cell.2020.08.026","article-title":"A Single-Dose Intranasal ChAd Vaccine Protects Upper and Lower Respiratory Tracts Against SARS-CoV-2","volume":"183","author":"Hassan","year":"2020","journal-title":"Cell"},{"key":"ref_6","doi-asserted-by":"crossref","unstructured":"Pilapitiya, D., Wheatley, A.K., and Tan, H.X. 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