Vaccine Production Program, Vaccine Research Center, National Institutes of Health, 9 W Watkins Mill Rd, Gaithersburg, MD, 20877, USA.
Complex Carbohydrate Research Center, University of Georgia, 315 Riverbend Rd, Athens, GA, 30602, USA.
Sci Rep. 2023 Jun 21;13(1):10053. doi: 10.1038/s41598-023-33088-0.
The glycosylation on the spike (S) protein of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the virus that causes COVID-19, modulates the viral infection by altering conformational dynamics, receptor interaction and host immune responses. Several variants of concern (VOCs) of SARS-CoV-2 have evolved during the pandemic, and crucial mutations on the S protein of the virus have led to increased transmissibility and immune escape. In this study, we compare the site-specific glycosylation and overall glycomic profiles of the wild type Wuhan-Hu-1 strain (WT) S protein and five VOCs of SARS-CoV-2: Alpha, Beta, Gamma, Delta and Omicron. Interestingly, both N- and O-glycosylation sites on the S protein are highly conserved among the spike mutant variants, particularly at the sites on the receptor-binding domain (RBD). The conservation of glycosylation sites is noteworthy, as over 2 million SARS-CoV-2 S protein sequences have been reported with various amino acid mutations. Our detailed profiling of the glycosylation at each of the individual sites of the S protein across the variants revealed intriguing possible association of glycosylation pattern on the variants and their previously reported infectivity. While the sites are conserved, we observed changes in the N- and O-glycosylation profile across the variants. The newly emerged variants, which showed higher resistance to neutralizing antibodies and vaccines, displayed a decrease in the overall abundance of complex-type glycans with both fucosylation and sialylation and an increase in the oligomannose-type glycans across the sites. Among the variants, the glycosylation sites with significant changes in glycan profile were observed at both the N-terminal domain and RBD of S protein, with Omicron showing the highest deviation. The increase in oligomannose-type happens sequentially from Alpha through Delta. Interestingly, Omicron does not contain more oligomannose-type glycans compared to Delta but does contain more compared to the WT and other VOCs. O-glycosylation at the RBD showed lower occupancy in the VOCs in comparison to the WT. Our study on the sites and pattern of glycosylation on the SARS-CoV-2 S proteins across the VOCs may help to understand how the virus evolved to trick the host immune system. Our study also highlights how the SARS-CoV-2 virus has conserved both N- and O- glycosylation sites on the S protein of the most successful variants even after undergoing extensive mutations, suggesting a correlation between infectivity/ transmissibility and glycosylation.
严重急性呼吸综合征冠状病毒 2（SARS-CoV-2）的刺突（S）蛋白上的糖基化修饰改变了病毒的构象动力学、受体相互作用和宿主免疫反应，从而调节病毒感染。在大流行期间，SARS-CoV-2 已经进化出几种关注的变体（VOCs），病毒 S 蛋白上的关键突变导致了传染性和免疫逃逸的增加。在这项研究中，我们比较了野生型武汉-Hu-1 株（WT）S 蛋白和 SARS-CoV-2 的五个 VOCs（Alpha、Beta、Gamma、Delta 和 Omicron）的特异性糖基化和整体糖组图谱。有趣的是，S 蛋白上的 N-和 O-糖基化位点在 Spike 突变体变体中高度保守，特别是在受体结合域（RBD）上的位点。糖基化位点的保守性值得注意，因为已经报告了超过 200 万个具有各种氨基酸突变的 SARS-CoV-2 S 蛋白序列。我们对变体中 S 蛋白各个位点的糖基化进行了详细的分析，揭示了糖基化模式与变体及其先前报道的感染性之间可能存在的关联。虽然这些位点是保守的，但我们观察到变体之间 N-和 O-糖基化谱发生了变化。新出现的变体对中和抗体和疫苗的抵抗力更高，表现为整个复杂型聚糖的丰度降低，带有岩藻糖和唾液酸，以及各位点寡甘露糖型聚糖的增加。在变体中，在 S 蛋白的 N 端结构域和 RBD 观察到糖基化谱发生显著变化的糖基化位点，其中 Omicron 的偏差最大。寡甘露糖型的增加从 Alpha 到 Delta 依次发生。有趣的是，与 Delta 相比，Omicron 中并不含有更多的寡甘露糖型聚糖，但与 WT 和其他 VOCs 相比，Omicron 中含有更多的寡甘露糖型聚糖。与 WT 相比，RBD 的 O-糖基化在 VOCs 中的占有率较低。我们对 SARS-CoV-2 S 蛋白在 VOCs 中的糖基化位点和模式的研究可能有助于了解病毒如何进化以欺骗宿主免疫系统。我们的研究还强调了 SARS-CoV-2 病毒如何在经历广泛突变后，即使在最成功的变体中，也保守了 S 蛋白上的 N-和 O-糖基化位点，这表明感染性/传染性和糖基化之间存在相关性。
