{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,3,26]],"date-time":"2026-03-26T18:07:55Z","timestamp":1774548475145,"version":"3.50.1"},"reference-count":33,"publisher":"MDPI AG","issue":"13","license":[{"start":{"date-parts":[[2023,6,24]],"date-time":"2023-06-24T00:00:00Z","timestamp":1687564800000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"name":"JSPS Grant-in-Aid for Scientific Research","award":["KAKENHI-15H04359 and 18H02385"],"award-info":[{"award-number":["KAKENHI-15H04359 and 18H02385"]}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["IJMS"],"abstract":"<jats:p>E. coli-expressed proteins could provide a rapid, cost-effective, and safe antigen for subunit vaccines, provided we can produce them in a properly folded form inducing neutralizing antibodies. Here, we use an E. coli-expressed SARS-CoV-2 receptor-binding domain (RBD) of the spike protein as a model to examine whether it yields neutralizing antisera with effects comparable to those generated by the S1 subunit of the spike protein (S1 or S1 subunit, thereafter) expressed in mammalian cells. We immunized 5-week-old Jcl-ICR female mice by injecting RBD (30 \u00b5g) and S1 subunit (5 \u00b5g) according to four schemes: two injections 8 weeks apart with RBD (RBD\/RBD), two injections with S1 (S1\/S1), one injection with RBD, and the second one with S1 (RBD\/S1), and vice versa (S1\/RBD). Ten weeks after the first injection (two weeks after the second injection), all combinations induced a strong immune response with IgG titer &gt; 105 (S1\/RBD &lt; S1\/S1 &lt; RBD\/S1 &lt; RBD\/RBD). In addition, the neutralization effect of the antisera ranked as S1\/RBD~RBD\/S1 (80%) &gt; S1\/S1 (56%) &gt; RBD\/RBD (42%). These results indicate that two injections with E. coli-expressed RBD, or mammalian-cell-produced spike S1 subunit alone, can provide some protection against SARS-CoV-2, but a mixed injection scheme yields significantly higher protection.<\/jats:p>","DOI":"10.3390\/ijms241310583","type":"journal-article","created":{"date-parts":[[2023,6,26]],"date-time":"2023-06-26T01:42:32Z","timestamp":1687743752000},"page":"10583","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":5,"title":["Antisera Produced Using an E. coli-Expressed SARS-CoV-2 RBD and Complemented with a Minimal Dose of Mammalian-Cell-Expressed S1 Subunit of the Spike Protein Exhibits Improved Neutralization"],"prefix":"10.3390","volume":"24","author":[{"given":"Takahiro","family":"Yoshizue","sequence":"first","affiliation":[{"name":"Department of Biotechnology and Life Science, Faculty of Engineering, Tokyo University of Agriculture and Technology, 2-24-16 Nakamachi, Koganei-shi 184-8588, Japan"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Subbaian","family":"Brindha","sequence":"additional","affiliation":[{"name":"Department of Biotechnology and Life Science, Faculty of Engineering, Tokyo University of Agriculture and Technology, 2-24-16 Nakamachi, Koganei-shi 184-8588, Japan"},{"name":"Institute of Global Innovation Research, Tokyo University of Agriculture and Technology, 3-8-1 Harumi-cho, Fuchu-shi 183-8538, Japan"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Rawiwan","family":"Wongnak","sequence":"additional","affiliation":[{"name":"Department of Biotechnology and Life Science, Faculty of Engineering, Tokyo University of Agriculture and Technology, 2-24-16 Nakamachi, Koganei-shi 184-8588, Japan"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Hitoshi","family":"Takemae","sequence":"additional","affiliation":[{"name":"Institute of Global Innovation Research, Tokyo University of Agriculture and Technology, 3-8-1 Harumi-cho, Fuchu-shi 183-8538, Japan"},{"name":"Center for Infectious Disease Epidemiology and Prevention Research, Tokyo University of Agriculture and Technology, 3-5-8 Saiwai-Cho, Fuchu-shi 183-8509, Japan"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-4187-3217","authenticated-orcid":false,"given":"Mami","family":"Oba","sequence":"additional","affiliation":[{"name":"Institute of Global Innovation Research, Tokyo University of Agriculture and Technology, 3-8-1 Harumi-cho, Fuchu-shi 183-8538, Japan"},{"name":"Center for Infectious Disease Epidemiology and Prevention Research, Tokyo University of Agriculture and Technology, 3-5-8 Saiwai-Cho, Fuchu-shi 183-8509, Japan"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Tetsuya","family":"Mizutani","sequence":"additional","affiliation":[{"name":"Institute of Global Innovation Research, Tokyo University of Agriculture and Technology, 3-8-1 Harumi-cho, Fuchu-shi 183-8538, Japan"},{"name":"Center for Infectious Disease Epidemiology and Prevention Research, Tokyo University of Agriculture and Technology, 3-5-8 Saiwai-Cho, Fuchu-shi 183-8509, Japan"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-3221-4295","authenticated-orcid":false,"given":"Yutaka","family":"Kuroda","sequence":"additional","affiliation":[{"name":"Department of Biotechnology and Life Science, Faculty of Engineering, Tokyo University of Agriculture and Technology, 2-24-16 Nakamachi, Koganei-shi 184-8588, Japan"},{"name":"Institute of Global Innovation Research, Tokyo University of Agriculture and Technology, 3-8-1 Harumi-cho, Fuchu-shi 183-8538, Japan"}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"1968","published-online":{"date-parts":[[2023,6,24]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"470","DOI":"10.1016\/S0140-6736(20)30185-9","article-title":"A novel coronavirus outbreak of global health concern","volume":"395","author":"Wang","year":"2020","journal-title":"Lancet"},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"155","DOI":"10.1038\/s41579-020-00468-6","article-title":"Coronavirus biology and replication: Implications for SARS-CoV-2","volume":"19","author":"Kratzel","year":"2021","journal-title":"Nat. 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