RBD-Based COVID-19 Vaccines: Technologies and Immune Responses

A special issue of Vaccines (ISSN 2076-393X). This special issue belongs to the section "COVID-19 Vaccines and Vaccination".

Deadline for manuscript submissions: 28 February 2027 | Viewed by 636

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National Institute of Allergy and Infectious Diseases (NIAID), Bethesda, MD, USA
Interests: vaccine development; conjugate vaccines; nanotechnology
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Special Issue Information

Dear Colleagues,

The emergence of the COVID-19 pandemic in 2019 led to unprecedented efforts in vaccine development. Effective vaccines using various platforms have played a vital role in controlling the pandemic. Initially, most subunit vaccines targeted the spike protein of SARS-CoV-2. However, vaccines based on the spike protein's receptor-binding domain (RBD) have also proven themselves to be effective. The neutralizing antibodies target the RBD, which is smaller than the whole spike protein. This focus can enhance manufacturing and help minimize non-neutralizing antibody production. This Special Issue invites submissions of original research, reviews, clinical trial results, and opinions related to RBD and spike protein-based vaccines, demonstrating the application of different vaccine technologies to induce immune response.

Dr. Puthupparampil Scaria
Guest Editor

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Keywords

  • RBD vaccine
  • COVID-19
  • vaccine
  • SARS-CoV-2

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Published Papers (1 paper)

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Research

12 pages, 812 KB  
Article
Poria cocos Polysaccharide Fraction PCP-II Enhances Humoral and Cellular Responses to a SARS-CoV-2 RBD Subunit Vaccine in Mice
by Mao Zhou, Jing Liu, Xiaotuan Zhang, Feihu Yan, Yuan Wu, Cheng Huang, Dan Xie and Bin Liu
Vaccines 2026, 14(5), 389; https://doi.org/10.3390/vaccines14050389 - 27 Apr 2026
Viewed by 360
Abstract
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 [...] Read more.
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 (6–8 weeks) were immunized on days 0, 7, and 21 with an RBD protein (20 μg) alone or formulated with Poria cocos polysaccharide fraction PCP-I or PCP-II (200 μg), 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-γ 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-γ-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-γ-related cellular responses, supporting its potential as a candidate polysaccharide adjuvant for protein subunit vaccines. Full article
(This article belongs to the Special Issue RBD-Based COVID-19 Vaccines: Technologies and Immune Responses)
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