SARS-CoV-2 subunit vaccine adjuvants and their signaling pathways

Vaccines are the agreed upon weapon against the COVID-19 pandemic. This review discusses about COVID-19 subunit vaccines adjuvants and their signaling pathways, which could provide a glimpse into the selection of appropriate adjuvants for prospective vaccine development studies.
In the introduction, a brief background about the SARS-CoV-2 pandemic, the vaccine development race and classes of vaccine adjuvants were provided. . The antigen, trial stage, and types of adjuvants were extracted from the included articles and thun assimilated. Finally, the pattern recognition receptors (PRRs), their classes, cognate adjuvants, and potential signaling pathways were comprehended.
Adjuvants are unsung heroes of subunit vaccines. The in silico studies are very vital in avoiding several costly trial errors and save much work times. The majority of the (pre)clinical studies are promising. It is encouraging that most of the selected adjuvants are novel. Much emphasis must be paid to the optimal paring of antigen-adjuvant-PRRs for obtaining the desired vaccine effect. A good subunit vaccine/adjuvant is one that has high efficacy, safety, dose sparing, and rapid seroconversion rate and broad spectrum of immune response. In the years to come, COVID-19 adjuvanted subunit vaccines are expected to have superior utility than any other vaccines for various reasons.

疫苗是公认的对抗2019冠状病毒病（COVID-19）大流行的有力武器。本综述探讨了新冠亚单位疫苗（subunit vaccines）佐剂（adjuvants）及其信号通路，可为前瞻性疫苗研发研究中合适佐剂的遴选提供参考。

引言部分简要介绍了严重急性呼吸综合征冠状病毒2（SARS-CoV-2）大流行的背景、疫苗研发的竞争态势以及疫苗佐剂的分类。研究人员从纳入的文献中提取了抗原、临床试验阶段以及佐剂类型，并随后进行了归纳整合。最后，本研究还对模式识别受体（pattern recognition receptors, PRRs）、其类别、同源佐剂以及潜在的信号通路进行了梳理与阐释。

佐剂是亚单位疫苗中默默发挥关键作用的无名英雄。计算机模拟（in silico）研究对于规避诸多昂贵的临床试验失误、节省大量研发工时至关重要。绝大多数（预）临床研究结果均表现出良好前景。令人振奋的是，所遴选的佐剂大多为新型佐剂。为获得理想的疫苗效应，需重点关注抗原-佐剂-模式识别受体的最优匹配。优质的亚单位疫苗/佐剂应具备高效性、安全性、剂量节省效应、快速血清转换率以及广谱免疫应答能力。未来，得益于诸多优势，佐剂化新冠亚单位疫苗有望展现出优于其他各类疫苗的应用价值。