{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2025,8,15]],"date-time":"2025-08-15T02:07:12Z","timestamp":1755223632697,"version":"3.43.0"},"reference-count":28,"publisher":"Frontiers Media SA","license":[{"start":{"date-parts":[[2025,8,12]],"date-time":"2025-08-12T00:00:00Z","timestamp":1754956800000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":["frontiersin.org"],"crossmark-restriction":true},"short-container-title":["Front. Microbiol."],"abstract":"<jats:p>As an immunogenic non-toxic mutant of diphtheria toxin (DT), cross-reacting material 197 (CRM197) exhibits a significant immunogenicity-enhancing effect on various pathogenic vaccines. However, its application in vaccines against highly pathogenic pathogens remains underexplored. In this study, we incorporated CRM197 into a severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) vaccine, aiming to identify a molecular adjuvant capable of inducing broad-spectrum neutralizing antibodies and to develop a subunit vaccine with stronger cross-reactivity, improved safety, and greater accessibility. Our findings revealed that compared to non-fused SARS-CoV-2 spike (S) protein receptor-binding domain (RBD) (designated sRBD), the fusion of CRM197 with the SARS-CoV-2\u202fS protein RBD (termed CRM-RBD) elicited stronger humoral immunity, Th1-biased cellular immune responses, and reduced immune evasion against SARS-CoV-2 variants in mice. Furthermore, mice immunized with CRM-RBD exhibited significantly lower mortality and reduced pulmonary pathology upon viral challenge. These results demonstrate that CRM197 substantially enhances the immunogenicity of SARS-CoV-2 vaccines, positioning it as an ideal candidate protein for developing SARS-CoV-2 vaccines with broader cross-reactivity.<\/jats:p>","DOI":"10.3389\/fmicb.2025.1650239","type":"journal-article","created":{"date-parts":[[2025,8,12]],"date-time":"2025-08-12T05:31:23Z","timestamp":1754976683000},"update-policy":"https:\/\/doi.org\/10.3389\/crossmark-policy","source":"Crossref","is-referenced-by-count":0,"title":["Enhancement of immunogenicity of SARS-CoV-2 spike protein expressed in Escherichia coli by fusion of the CRM197 functional domain"],"prefix":"10.3389","volume":"16","author":[{"given":"Xibing","family":"Yu","sequence":"first","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Yinmeng","family":"Yang","sequence":"additional","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Miao","family":"Zhang","sequence":"additional","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Qiantong","family":"Shen","sequence":"additional","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Yun","family":"Zhu","sequence":"additional","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Tong","family":"An","sequence":"additional","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Siqi","family":"Li","sequence":"additional","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Kexin","family":"Zhang","sequence":"additional","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Shuaiyao","family":"Lu","sequence":"additional","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Shaohong","family":"Lu","sequence":"additional","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Fangcheng","family":"Zhuang","sequence":"additional","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Meng","family":"Gao","sequence":"additional","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"1965","published-online":{"date-parts":[[2025,8,12]]},"reference":[{"key":"ref1","doi-asserted-by":"publisher","first-page":"268","DOI":"10.1038\/s41586-021-03681-2","article-title":"Immunogenicity of Ad26.COV2.S vaccine against SARS-CoV-2 variants in humans","volume":"596","author":"Alter","year":"2021","journal-title":"Nature"},{"key":"ref2","doi-asserted-by":"publisher","first-page":"11139","DOI":"10.1039\/c3cp55219e","article-title":"Studies of protein folding and dynamics using single molecule fluorescence spectroscopy","volume":"16","author":"Basak","year":"2014","journal-title":"Phys. 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