Department of Infectious Diseases, King's College London, London, United Kingdom.
UKRI Genotype-2-Phenotype Consortium, London, United Kingdom.
J Virol. 2022 Dec 14;96(23):e0125022. doi: 10.1128/jvi.01250-22. Epub 2022 Nov 9.
The appearance of new dominant variants of concern (VOC) of severe acute respiratory syndrome coronavirus type 2 (SARS-CoV-2) threatens the global response to the coronavirus disease 2019 (COVID-19) pandemic. Of these, the alpha variant (also known as B.1.1.7), which appeared initially in the United Kingdom, became the dominant variant in much of Europe and North America in the first half of 2021. The spike (S) glycoprotein of alpha acquired seven mutations and two deletions compared to the ancestral virus, including the P681H mutation adjacent to the polybasic cleavage site, which has been suggested to enhance S cleavage. Here, we show that the alpha spike protein confers a level of resistance to beta interferon (IFN-β) in human lung epithelial cells. This correlates with resistance to an entry restriction mediated by interferon-induced transmembrane protein 2 (IFITM2) and a pronounced infection enhancement by IFITM3. Furthermore, the P681H mutation is essential for resistance to IFN-β and context-dependent resistance to IFITMs in the alpha S. P681H reduces dependence on endosomal cathepsins, consistent with enhanced cell surface entry. However, reversion of H681 does not reduce cleaved spike incorporation into particles, indicating that it exerts its effect on entry and IFN-β downstream of furin cleavage. Overall, we suggest that, in addition to adaptive immune escape, mutations associated with VOC may well also confer a replication and/or transmission advantage through adaptation to resist innate immune mechanisms. Accumulating evidence suggests that variants of concern (VOC) of SARS-CoV-2 evolve to evade the human immune response, with much interest focused on mutations in the spike protein that escape from antibodies. However, resistance to the innate immune response is essential for efficient viral replication and transmission. Here, we show that the alpha (B.1.1.7) VOC of SARS-CoV-2 is substantially more resistant to type I interferons than the parental Wuhan-like virus. This correlates with resistance to the antiviral protein IFITM2 and enhancement by its paralogue IFITM3. The key determinant of this is a proline-to-histidine change at position 681 in S adjacent to the furin cleavage site, which in the context of the alpha spike modulates cell entry pathways of SARS-CoV-2. Reversion of the mutation is sufficient to restore interferon and IFITM2 sensitivity, highlighting the dynamic nature of the SARS CoV-2 as it adapts to both innate and adaptive immunity in the humans.
新型严重急性呼吸综合征冠状病毒 2 型（SARS-CoV-2）的主要变异株（VOC）的出现威胁着全球对 2019 年冠状病毒病（COVID-19）大流行的应对。其中，最初出现在英国的阿尔法变异株（也称为 B.1.1.7），在 2021 年上半年成为欧洲和北美的主要变异株。与原始病毒相比，阿尔法的刺突（S）糖蛋白获得了 7 个突变和 2 个缺失，包括紧邻多碱性切割位点的 P681H 突变，这被认为增强了 S 的切割。在这里，我们表明阿尔法刺突蛋白赋予了人类肺上皮细胞对β干扰素（IFN-β）的一定抗性。这与对干扰素诱导跨膜蛋白 2（IFITM2）介导的进入限制的抗性以及 IFITM3 的明显感染增强相关。此外，P681H 突变对于抵抗 IFN-β和 α S 中 IFITM 的上下文相关抗性是必需的。P681H 降低了对内体组织蛋白酶的依赖性，与增强的细胞表面进入一致。然而，H681 的回复并没有减少切割的刺突蛋白掺入到颗粒中，表明它在弗林切割后对进入和 IFN-β发挥作用。总体而言，我们认为，除了适应性免疫逃逸外，与 VOC 相关的突变也可能通过适应来抵抗先天免疫机制，从而赋予复制和/或传播优势。越来越多的证据表明，严重急性呼吸综合征冠状病毒 2 型的关注变异株（VOC）进化以逃避人类免疫反应，人们对刺突蛋白中的突变以逃避抗体的关注很多。然而，抵抗先天免疫反应对于有效的病毒复制和传播是必不可少的。在这里，我们表明，与亲本武汉样病毒相比，α（B.1.1.7）VOC 的 SARS-CoV-2 对 I 型干扰素的抗性要强得多。这与抗病毒蛋白 IFITM2 的抗性和其同源物 IFITM3 的增强相关。这种情况的关键决定因素是 S 中靠近弗林切割位点的第 681 位脯氨酸到组氨酸的变化，这在 α 刺突的背景下调节了 SARS-CoV-2 的进入途径。突变的回复足以恢复干扰素和 IFITM2 的敏感性，突出了 SARS CoV-2 的动态性质，因为它适应了人类的先天免疫和适应性免疫。
