IrsiCaixa AIDS Research Institute, Badalona, Spain.
Unitat Mixta d'Investigació IRTA-UAB en Sanitat Animal, Centre de Recerca en Sanitat Animal (CReSA), Campus de la Universitat Autònoma de Barcelona (UAB), Barcelona, Spain.
Front Immunol. 2023 Dec 4;14:1291972. doi: 10.3389/fimmu.2023.1291972. eCollection 2023.
Most COVID-19 vaccines are based on the SARS-CoV-2 Spike glycoprotein (S) or their subunits. However, S shows some structural instability that limits its immunogenicity and production, hampering the development of recombinant S-based vaccines. The introduction of the K986P and V987P (S-2P) mutations increases the production and immunogenicity of the recombinant S trimer, suggesting that these two parameters are related. Nevertheless, S-2P still shows some molecular instability and it is produced with low yield. Here we described a novel set of mutations identified by molecular modeling and located in the S2 region of the S-2P that increase its production up to five-fold. Besides their immunogenicity, the efficacy of two representative S-2P-based mutants, S-29 and S-21, protecting from a heterologous SARS-CoV-2 Beta variant challenge was assayed in K18-hACE2 mice (an animal model of severe SARS-CoV-2 disease) and golden Syrian hamsters (GSH) (a moderate disease model). S-21 induced higher level of WH1 and Delta variants neutralizing antibodies than S-2P in K18-hACE2 mice three days after challenge. Viral load in nasal turbinate and oropharyngeal samples were reduced in S-21 and S-29 vaccinated mice. Despite that, only the S-29 protein protected 100% of K18-hACE2 mice from severe disease. When GSH were analyzed, all immunized animals were protected from disease development irrespectively of the immunogen they received. Therefore, the higher yield of S-29, as well as its improved immunogenicity and efficacy protecting from the highly pathogenic SARS-CoV-2 Beta variant, pinpoint the S-29 mutant as an alternative to the S-2P protein for future SARS-CoV-2 vaccine development.
大多数 COVID-19 疫苗都是基于 SARS-CoV-2 的刺突糖蛋白（S）或其亚单位。然而，S 表现出一些结构不稳定性，限制了其免疫原性和生产，阻碍了基于重组 S 的疫苗的发展。引入 K986P 和 V987P（S-2P）突变会增加重组 S 三聚体的产量和免疫原性，这表明这两个参数是相关的。尽管如此，S-2P 仍然表现出一些分子不稳定性，并且产量较低。在这里，我们通过分子建模鉴定了一组新的突变，并将其定位在 S-2P 的 S2 区域，使产量增加了五倍。除了它们的免疫原性之外，还在 K18-hACE2 小鼠（一种严重 SARS-CoV-2 疾病的动物模型）和金黄地鼠（一种中度疾病模型）中检测了两种代表性的基于 S-2P 的突变体 S-29 和 S-21 的功效，以保护它们免受异源 SARS-CoV-2 Beta 变体的挑战。在挑战后三天，S-21 在 K18-hACE2 小鼠中诱导了比 S-2P 更高水平的 WH1 和 Delta 变体中和抗体。在接种 S-21 和 S-29 的小鼠中，鼻鼻甲和口咽样本中的病毒载量减少。尽管如此，只有 S-29 蛋白能使 100%的 K18-hACE2 小鼠免受严重疾病的侵害。当分析金黄地鼠时，无论它们接受的免疫原如何，所有免疫的动物都免受疾病发展的影响。因此，S-29 的产量更高，以及其改善的免疫原性和功效，可以保护免受高致病性 SARS-CoV-2 Beta 变体的侵害，这表明 S-29 突变体是未来 SARS-CoV-2 疫苗开发的替代 S-2P 蛋白的选择。
