Skip to main content

ORIGINAL RESEARCH article

Front. Cell. Infect. Microbiol.

Sec. Adaptive immunity in infection

Volume 15 - 2025 | doi: 10.3389/fcimb.2025.1548787

Repeated-dose toxicity and immunogenicity evaluation of a recombinant subunit COVID-19 vaccine (ZF2001) in rats

Provisionally accepted
Ruimin Sun Ruimin Sun 1,2Lijuan Xia Lijuan Xia 1,2Guangbiao She Guangbiao She 3,4Jinrong Li Jinrong Li 1Yiru Wang Yiru Wang 1,5Yunxiang Chen Yunxiang Chen 1,2Qian Yang Qian Yang 1Siming Zhang Siming Zhang 1Fang Liu Fang Liu 1Ying Chen Ying Chen 1Liyan Zhang Liyan Zhang 1Chengda Zhang Chengda Zhang 1Wanqiang Lv Wanqiang Lv 1,2Enqi Huang Enqi Huang 3,4*Lijiang Zhang Lijiang Zhang 1,2,6*
  • 1 Key Laboratory of Drug Safety Evaluation and Research of Zhejiang Province, Center of Safety Evaluation and Research, Hangzhou Medical College, Hangzhou 310053, China, Hangzhou, Jiangsu Province, China
  • 2 Engineering Research Center of Novel Vaccine of Zhejiang Province, Hangzhou Medical College, Hangzhou 310013, China, Hangzhou, Jiangsu Province, China
  • 3 Anhui Zhifei Longcom Biopharmaceutical Co., Ltd., HeFei 230088, China, Hefei, Anhui Province, China
  • 4 Recombinant vaccine research and development Joint Laboratory of Anhui Province, HeFei 230088, China, Hefei, Anhui Province, China
  • 5 Faculty of Chinese Medicine, Macau University of Science and Technology, Macau, Macau Region, China
  • 6 Qingshan Lake Science and Technology Innovation Center, Hangzhou Medical College, Hangzhou 311305, China, Hangzhou, Jiangsu Province, China

The final, formatted version of the article will be published soon.

    Coronavirus disease 19 (COVID-19), caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), had given rise to a massive epidemic. Owing to the high morbidity and mortality of COVID-19 and the lack of effective therapies, safe and effective vaccination is the optimum choice for controlling this epidemic and preventing infection. The protein subunit vaccine ZF2001, which targets the receptor-binding domain (RBD) protein of SARS-CoV-2, has a significant protective effect against COVID-19. At the beginning of the COVID-19 epidemic, to promote the early approval of ZF2001 for clinical trials by the National Medical Products Administration of China (NMPA), a comprehensive evaluation of its toxicity in vivo was warranted. In the present study, a major part of the above series of studies, we evaluated the safety, immunogenicity and efficacy of the ZF2001 vaccine for the first time in adult Sprague Dawley (SD) rats. The male and female rats were administered three doses of the ZF2001 vaccine (25 μg or 50 μg NCP-RBD protein/dose, containing the aluminum-based adjuvant). The safety profile of ZF2001 was assessed by observing the general health status, local toxicity at the site of administration, immunotoxicity, immunogenicity, blood chemistry and hematology parameters in SD rats. In general, our results indicated that the ZF2001 vaccine did not induce significant systemic toxicity in rats, with a no-observed adverse effect level (NOAEL) of 50 μg NCP-RBD protein/rat. Moreover, the ZF2001 vaccine showed good immunogenicity by inducing the production of specific IgG antibodies in rats after three consecutive immunizations. In addition, histological examination revealed recoverable inflammatory changes in quadricep muscles and adjacent lymph nodes at the vaccine injection site. In summary, our systematic toxicology study proves the safety, tolerability and immunogenicity of the ZF2001 vaccine, which further supports the results of clinical trials of ZF2001.

    Keywords: COVID-19, Subunit protein vaccine, ZF2001, Repeated-dose toxicity study, immune response

    Received: 20 Dec 2024; Accepted: 24 Mar 2025.

    Copyright: © 2025 Sun, Xia, She, Li, Wang, Chen, Yang, Zhang, Liu, Chen, Zhang, Zhang, Lv, Huang and Zhang. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) or licensor are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

    * Correspondence:
    Enqi Huang, Anhui Zhifei Longcom Biopharmaceutical Co., Ltd., HeFei 230088, China, Hefei, Anhui Province, China
    Lijiang Zhang, Key Laboratory of Drug Safety Evaluation and Research of Zhejiang Province, Center of Safety Evaluation and Research, Hangzhou Medical College, Hangzhou 310053, China, Hangzhou, Jiangsu Province, China

    Disclaimer: All claims expressed in this article are solely those of the authors and do not necessarily represent those of their affiliated organizations, or those of the publisher, the editors and the reviewers. Any product that may be evaluated in this article or claim that may be made by its manufacturer is not guaranteed or endorsed by the publisher.

    Research integrity at Frontiers

    Man ultramarathon runner in the mountains he trains at sunset

    94% of researchers rate our articles as excellent or good

    Learn more about the work of our research integrity team to safeguard the quality of each article we publish.


    Find out more