{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,4,29]],"date-time":"2026-04-29T06:04:25Z","timestamp":1777442665352,"version":"3.51.4"},"reference-count":36,"publisher":"MDPI AG","issue":"5","license":[{"start":{"date-parts":[[2026,4,27]],"date-time":"2026-04-27T00:00:00Z","timestamp":1777248000000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/501100002767","name":"Hunan Province Natural Science Foundation of China","doi-asserted-by":"publisher","award":["2023JJ50141"],"award-info":[{"award-number":["2023JJ50141"]}],"id":[{"id":"10.13039\/501100002767","id-type":"DOI","asserted-by":"publisher"}]},{"DOI":"10.13039\/501100010451","name":"the Health Commission of Hunan Province","doi-asserted-by":"publisher","award":["202211004302"],"award-info":[{"award-number":["202211004302"]}],"id":[{"id":"10.13039\/501100010451","id-type":"DOI","asserted-by":"publisher"}]},{"name":"Prevention and Control of Emerging and Major Infectious Diseases-National Science and Technology Major Project","award":["2025ZD01900700"],"award-info":[{"award-number":["2025ZD01900700"]}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Vaccines"],"abstract":"<jats:p>Background: The emergence of SARS-CoV-2 variants necessitates the development of effective adjuvants to enhance subunit vaccine immunogenicity. Safe adjuvants are essential to enhance the immunogenicity of SARS-CoV-2 receptor-binding domain (RBD) subunit vaccines. Traditional Chinese medicine polysaccharides are attractive candidates due to their immunomodulatory properties. Methods: Female BALB\/c mice (6\u20138 weeks) were immunized on days 0, 7, and 21 with an RBD protein (20 \u03bcg) alone or formulated with Poria cocos polysaccharide fraction PCP-I or PCP-II (200 \u03bcg), Isatis indigotica polysaccharide, or aluminum adjuvant; PBS served as a control. RBD-specific total IgG and subclasses were quantified by ELISA on day 7 after the third immunization. Neutralizing antibody titers were measured by a pseudovirus assay on days 14, 28, and 56 after the first immunization. Splenic CD19+ B cells were analyzed by flow cytometry, and antigen-stimulated IFN-\u03b3 and IL-4 spot-forming cells were quantified by ELISpot. Results: PCP-II significantly increased RBD-specific total IgG and IgG1 compared with RBD alone and other formulations, whereas IgG2a and IgG2b remained unchanged. Both PCP-I and PCP-II increased neutralizing titers versus RBD alone, and PCP-II showed an earlier and sustained increase in neutralizing responses through day 56. PCP-II showed a non-significant increase in splenic CD19+ B cell frequency. PCP-I and PCP-II markedly increased IFN-\u03b3-secreting splenocytes without increasing IL-4, indicating enhanced antigen-specific cellular responses. Conclusion: In this comparative evaluation of traditional Chinese medicine polysaccharide candidates in a SARS-CoV-2 RBD subunit vaccine model, PCP-II showed the most prominent adjuvant activity. PCP-II enhanced antigen-specific humoral immunogenicity, improved neutralizing antibody responses, and was associated with increased IFN-\u03b3-related cellular responses, supporting its potential as a candidate polysaccharide adjuvant for protein subunit vaccines.<\/jats:p>","DOI":"10.3390\/vaccines14050389","type":"journal-article","created":{"date-parts":[[2026,4,28]],"date-time":"2026-04-28T11:33:37Z","timestamp":1777376017000},"page":"389","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":0,"title":["Poria cocos Polysaccharide Fraction PCP-II Enhances Humoral and Cellular Responses to a SARS-CoV-2 RBD Subunit Vaccine in Mice"],"prefix":"10.3390","volume":"14","author":[{"given":"Mao","family":"Zhou","sequence":"first","affiliation":[{"name":"Department of Clinical Laboratory, Second Affiliated Hospital, Hengyang Medical School, University of South China, Hengyang 421001, China"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Jing","family":"Liu","sequence":"additional","affiliation":[{"name":"Disinfection Supply Center, Second Affiliated Hospital, Hengyang Medical School, University of South China, Hengyang 421001, China"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Xiaotuan","family":"Zhang","sequence":"additional","affiliation":[{"name":"Department of Clinical Laboratory, Second Affiliated Hospital, Hengyang Medical School, University of South China, Hengyang 421001, China"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Feihu","family":"Yan","sequence":"additional","affiliation":[{"name":"Key Laboratory of Jilin Province for Zoonosis Prevention and Control, Changchun Veterinary Research Institute, Chinese Academy of Agricultural Sciences, State Key Laboratory of Pathogen and Biosecurity, Changchun 130122, China"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Yuan","family":"Wu","sequence":"additional","affiliation":[{"name":"Department of Clinical Laboratory, Second Affiliated Hospital, Hengyang Medical School, University of South China, Hengyang 421001, China"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Cheng","family":"Huang","sequence":"additional","affiliation":[{"name":"Department of Clinical Laboratory, Second Affiliated Hospital, Hengyang Medical School, University of South China, Hengyang 421001, China"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Dan","family":"Xie","sequence":"additional","affiliation":[{"name":"Department of Clinical Laboratory, Hengnan County People\u2019s Hospital, Hengyang 421100, China"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Bin","family":"Liu","sequence":"additional","affiliation":[{"name":"Department of Clinical Laboratory, Second Affiliated Hospital, Hengyang Medical School, University of South China, Hengyang 421001, China"}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"1968","published-online":{"date-parts":[[2026,4,27]]},"reference":[{"key":"ref_1","unstructured":"World Health Organization (2025, January 10). 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