König-Beihammer Julia, Vavra Ulrike, Shin Yun-Ji, Veit Christiane, Grünwald-Gruber Clemens, Gillitschka Yasmin, Huber Jasmin, Hofner Manuela, Vierlinger Klemens, Mitteregger Dieter, Weinhäusel Andreas, Strasser Richard
Department of Applied Genetics and Cell Biology, Institute of Plant Biotechnology and Cell Biology, University of Natural Resources and Life Sciences, Vienna, Austria.
Core Facility Mass Spectrometry, University of Natural Resources and Life Sciences Vienna, Muthgasse, Austria.
Front Chem. 2022 Feb 1;9:816544. doi: 10.3389/fchem.2021.816544. eCollection 2021.
Glycosylation of viral envelope proteins is important for infectivity and immune evasion. The SARS-CoV-2 spike protein is heavily glycosylated and host-derived glycan modifications contribute to the formation of specific immunogenic epitopes, enhance the virus-cell interaction or affect virus transmission. On recombinant viral antigens used as subunit vaccines or for serological assays, distinct glycan structures may enhance the immunogenicity and are recognized by naturally occurring antibodies in human sera. Here, we performed an glycoengineering approach to produce recombinant variants of the SARS-CoV-2 receptor-binding domain (RBD) with blood group antigens in plants. SARS-CoV-2 RBD and human glycosyltransferases for the blood group ABH antigen formation were transiently co-expressed in leaves. Recombinant RBD was purified and the formation of complex N-glycans carrying blood group A antigens was shown by immunoblotting and MS analysis. Binding to the cellular ACE2 receptor and the conformation-dependent CR3022 antibody showed that the RBD glycosylation variants carrying blood group antigens were functional. Analysis of sera from RBD-positive and RBD-negative individuals revealed further that non-infected RBD-negative blood group O individuals have antibodies that strongly bind to RBD modified with blood group A antigen structures. The binding of IgGs derived from sera of non-infected RBD-negative blood group O individuals to blood group A antigens on SARS-CoV-2 RBD suggests that these antibodies could provide some degree of protection from virus infection.
病毒包膜蛋白的糖基化对于感染性和免疫逃逸至关重要。严重急性呼吸综合征冠状病毒2（SARS-CoV-2）刺突蛋白高度糖基化，宿主来源的聚糖修饰有助于形成特定的免疫原性表位，增强病毒与细胞的相互作用或影响病毒传播。在用作亚单位疫苗或用于血清学检测的重组病毒抗原上，不同的聚糖结构可能增强免疫原性，并被人血清中的天然抗体识别。在此，我们采用糖工程方法在植物中生产带有血型抗原的SARS-CoV-2受体结合域（RBD）的重组变体。SARS-CoV-2 RBD和用于形成ABH血型抗原的人糖基转移酶在叶片中瞬时共表达。对重组RBD进行纯化，并通过免疫印迹和质谱分析显示了携带A型血型抗原的复合N-聚糖的形成。与细胞血管紧张素转换酶2（ACE2）受体和构象依赖性CR3022抗体的结合表明，携带血型抗原的RBD糖基化变体具有功能。对RBD阳性和RBD阴性个体血清的分析进一步显示，未感染的RBD阴性O型血个体具有能与A型血型抗原修饰的RBD强烈结合的抗体。未感染的RBD阴性O型血个体血清中的免疫球蛋白G（IgG）与SARS-CoV-2 RBD上的A型血型抗原的结合表明，这些抗体可能提供一定程度的病毒感染防护。
