針對新型冠狀病毒刺突蛋白受體結合區開發新冠肺炎次世代疫苗

Development of COVID-19 next generation vaccines targeting SARS-CoV-2 spike receptor binding domain

李逸容(I-Jung Lee)

指導教授 ： 陶秘華

國立臺灣大學/醫學院/微生物學研究所/博士(2023年)

https://doi.org/10.6342/NTU202210196

摘要

儘管目前已有數個新冠肺炎疫苗通過認證或可緊急使用，但疫苗的安全性、對抗新型冠狀病毒變異株的能力及長期的保護效力仍是需要關注及改善的問題。在這篇論文研究中，我們首先利用奈米疫苗技術平台，結合新型冠狀病毒刺突蛋白受體結合區，開發出ASD254蛋白奈米疫苗。實驗證實ASD254可有效刺激高效價的中和性抗體，保護免疫小鼠對抗新型冠狀病毒感染。此外，高效價的中和性抗體可在小鼠體內維持至少一年而沒有顯著下降，並有效中和新型冠狀病毒高關注變異株。另一方面，由於病毒快速突變，開發針對變異株的次世代疫苗也是當務之急。我們利用mRNA疫苗平台，快速設計及研發出一系列針對變異株的疫苗。我們以近兩次大流行的Delta和Omicron變異株為模板，開發以Delta和Omicron為標的的次世代疫苗。另外，也製作了含有Delta mRNA和Omicron mRNA的二價疫苗和整合這兩種變異株刺突蛋白受體結合區上所有突變位置的Hybrid疫苗。實驗發現接種Omicron特異性及Hybrid疫苗可在小鼠體內誘發高效價針對Omicron變異株的中和性抗體，但無法有效中和原始株及其它變異株，而WT、Delta特異性和二價疫苗則可針對不同的變異株產生有效的中和性抗體，但對Omicron變異株的中和效果較差。另一方面，若將這系列變異株疫苗作為追加劑疫苗使用，則所有變異株疫苗均可刺激免疫反應，引發廣效的中和性抗體，其中Hybrid疫苗能誘發最高效價的中和性抗體對抗 Omicron 變異株。本研究中，我們開發了兩種新冠肺炎次世代疫苗。第一部份的奈米疫苗可有效提高蛋白的免疫原性，產生廣效且持久的中和性抗體反應。第二部份針對變異株的疫苗，則證實我們可以快速開發疫苗，以因應新興變異株爆發。

關鍵字

新型冠狀病毒 ； 刺突蛋白受體結合區 ； 奈米疫苗 ； 信使核糖核酸疫苗 ； 廣效性中和抗體 ； 持久性中和抗體 ； 高關注變異株

並列摘要

Numerous vaccines have been developed to address the current COVID-19 pandemic, but safety, cross-neutralizing efficacy and long-term protectivity of currently approved vaccines are still important issues. In this study, we first developed a subunit vaccine, ASD254, by using a nanoparticle vaccine platform to encapsulate the SARS-CoV-2 spike receptor-binding domain (RBD) protein. ASD254 induced high titers of neutralizing antibodies and protective immune responses against SARS-CoV-2 challenge. Besides, the neutralizing antibodies in vaccinated mice were durable for at least 1 year and effective against SARS-CoV-2 variants of concern. These results indicate that ASD254 is a promising nanoparticle vaccine with great immunogenicity and stability to be an alternative option in controlling upcoming waves of COVID-19. On the other hand, with the continuous emergence of new SARS-CoV-2 variants, a next-generation vaccine that uses mutant RBD as antigen in response to the circulating variants is also a top priority. In this part, we took the advantage of mRNA vaccine platform to rapidly design and develop a panel of variant-specific vaccines. The RBD sequences of two dominant strains in current wave were used to develop Delta-specific and Omicron-specific vaccines. In addition, a “Hybrid” vaccine that uses the RBD containing all 16 point-mutations shown in Omicron and Delta variants, as well as a bivalent vaccine composed of both Omicron and Delta RBD mRNA was also included. In naïve mice, Hybrid vaccine generated strong Omicron-specific neutralizing antibodies as well as low but significant titers against other variants, while Omicron vaccine elicited neutralizing antibodies only limited to Omicron. On the other hand, wild-type, Delta, and Bivalent vaccines induced neutralizing antibodies against tested variants but lower antibody response against Omicron. While using as third booster dose, all these vaccines induced broad neutralizing antibodies in previously wild-type vaccine immunized mice with Hybrid vaccine stands out to elicit most potent titer of neutralizing antibodies against Omicron. In summary, we established two next-generation vaccines against SARS-CoV-2 in this study. The nanoparticle vaccine improves the immunogenicity of RBD protein and induces durable cross-neutralizing antibody responses. Generation of variant-specific RBD mRNA vaccines is a proof-of-concept for rapid vaccine development to address emerging variant outbreak. Both technologies are valuable vaccine platforms for the development of vaccines against COVID-19 and other emerging infectious diseases.

並列關鍵字

SARS-CoV-2 ； spike receptor-binding domain (RBD) ； nanoparticle vaccine ； mRNA vaccine ； cross-neutralizing antibody response ； durable neutralizing antibody response ； variants of concern

參考文獻

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