A Poly-Lysine-Based RBD Mucosal Vaccine Induces Potent Antibody Responses in Mice

Xu, Huifang; Wang, Han; Sun, Peng; Wang, Tiantian; Zhang, Bin; Hou, Xuchen; Wu, Jun; Liu, Bo

doi:10.3390/vaccines13060582

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A Poly-Lysine-Based RBD Mucosal Vaccine Induces Potent Antibody Responses in Mice

by

Huifang Xu

¹,

Han Wang

¹,

Peng Sun

^1,2,

Tiantian Wang

¹,

Bin Zhang

¹,

Xuchen Hou

¹,

Jun Wu

^1,* and

Bo Liu

^1,*

¹

Laboratory of Advanced Biotechnology, Beijing Institute of Biotechnology, 20 Dongdajie Street, Fengtai District, Beijing 100071, China

²

School of Basic Medical Sciences, Tsinghua University, No. 30 Shuangqing Road, Haidian District, Beijing 100084, China

^*

Authors to whom correspondence should be addressed.

Vaccines 2025, 13(6), 582; https://doi.org/10.3390/vaccines13060582

Submission received: 24 April 2025 / Revised: 23 May 2025 / Accepted: 27 May 2025 / Published: 29 May 2025

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Abstract

(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.

Keywords: SARS-CoV-2; RBD; poly-lysine; mucosal vaccine; subunit vaccine

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MDPI and ACS Style

Xu, H.; Wang, H.; Sun, P.; Wang, T.; Zhang, B.; Hou, X.; Wu, J.; Liu, B. A Poly-Lysine-Based RBD Mucosal Vaccine Induces Potent Antibody Responses in Mice. Vaccines 2025, 13, 582. https://doi.org/10.3390/vaccines13060582

AMA Style

Xu H, Wang H, Sun P, Wang T, Zhang B, Hou X, Wu J, Liu B. A Poly-Lysine-Based RBD Mucosal Vaccine Induces Potent Antibody Responses in Mice. Vaccines. 2025; 13(6):582. https://doi.org/10.3390/vaccines13060582

Chicago/Turabian Style

Xu, Huifang, Han Wang, Peng Sun, Tiantian Wang, Bin Zhang, Xuchen Hou, Jun Wu, and Bo Liu. 2025. "A Poly-Lysine-Based RBD Mucosal Vaccine Induces Potent Antibody Responses in Mice" Vaccines 13, no. 6: 582. https://doi.org/10.3390/vaccines13060582

APA Style

Xu, H., Wang, H., Sun, P., Wang, T., Zhang, B., Hou, X., Wu, J., & Liu, B. (2025). A Poly-Lysine-Based RBD Mucosal Vaccine Induces Potent Antibody Responses in Mice. Vaccines, 13(6), 582. https://doi.org/10.3390/vaccines13060582

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A Poly-Lysine-Based RBD Mucosal Vaccine Induces Potent Antibody Responses in Mice

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