新型冠状病毒刺突蛋白的变异及其对中和活性的影响

2019年底发生的COVID-19疫情迅速传播至世界各地, 使全球公共卫生体系面临严峻考验。随着疫情的持续, 新型冠状病毒(severe acute respiratory syndrane coronavirus 2, SARS-CoV-2)变异株正在不断涌现。特别是病毒刺突蛋白的突变, 可以引起病毒感染性和抗原性改变, 从而导致病毒传染性增加, 以及现有疫苗保护效力的下降, 由此引起了流行毒株的替换。这也是目前疫情未得到有效控制的原因之一。目前主要的流行变异株都出现了一定程度的特性改变, 部分变异株与原始株相比对中和单抗、免疫血清及恢复期血清的中和敏感性出现了一定程度的下降。变异株的产生既与病毒本身特点有关, 也与传播宿主改变、免疫低下人群的慢性感染有关。应密切关注和监测不断出现的变异株, 并对其功能特性进行系统研究, 为疫苗研发和免疫策略的制定提供参考。     

Mutations of SARS-CoV-2 spike protein: Implications on immune evasion and vaccine-induced immunity

Responsible for more than 4.9 million deaths so far, COVID-19, caused by SARS-CoV-2, is instigating devastating effects on the global health care system whose impacts could be longer for the years to come. Acquiring a comprehensive knowledge of host-virus interaction is critical for designing effective vaccines and/or drugs. Understanding the evolution of the virus and the impact of genetic variability on host immune evasion and vaccine efficacy is helpful to design novel strategies to minimize the effects of the emerging variants of concern (VOC). Most vaccines under development and/or in current use target the spike protein owning to its unique function of host receptor binding, relatively conserved nature, potent immunogenicity in inducing neutralizing antibodies, and being a good target of T cell responses. However, emerging SARS-CoV-2 strains are exhibiting variability on the spike protein which could affect the efficacy of vaccines and antibody-based therapies in addition to enhancing viral immune evasion mechanisms. Currently, the degree to which mutations on the spike protein affect immunity and vaccination, and the ability of the current vaccines to confer protection against the emerging variants attracts much attention. This review discusses the implications of SARS-CoV-2 spike protein mutations on immune evasion and vaccine-induced immunity and forward directions which could contribute to future studies focusing on designing effective vaccines and/or immunotherapies to consider viral evolution. Combining vaccines derived from different regions of the spike protein that boost both the humoral and cellular wings of adaptive immunity could be the best options to cope with the emerging VOC.     

Antibody response against SARS-CoV-2 spike protein and nucleoprotein evaluated by four automated immunoassays and three ELISAs

ObjectivesThe aim was to determine the antibody response against SARS-CoV-2 spike protein and nucleoprotein using four automated immunoassays and three ELISAs for the detection of total Ig antibodies (Roche) or IgG (Abbott, Diasorin, Snibe, Euroimmun, Mikrogen) in COVID-19 patients.MethodsSensitivity and dynamic trend to seropositivity were evaluated in 233 samples from 114 patients with moderate, severe or critical COVID-19 confirmed with PCR on nasopharyngeal swab. Specificity was evaluated in 113 samples collected before January 2020, including 24 samples from patients with non-SARS coronavirus infection.ResultsSensitivity for all assays was 100% (95% confidence interval 83.7–100) 3 weeks after onset of symptoms. Specificity varied between 94.7% (88.7–97.8) and 100% (96.1–100). Calculated at the cut-offs that corresponded to a specificity of 95% and 97.5%, Roche had the highest sensitivity (85.0% (79.8–89.0) and 81.1% (76.6–85.7), p < 0.05 except vs. Abbott). Seroconversion occurred on average 2 days earlier for Roche total Ig anti-N and the three IgG anti-N assays (Abbott, Mikrogen, Euroimmun) than for the two IgG anti-S assays (Diasorin, Euroimmun) (≥50% seroconversion day 9–10 vs. day 11–12 and p < 0.05 for percent seropositive patients day 9–10 to 17–18). There was no significant difference in the IgG antibody time to seroconversion between critical and non-critical patients.DiscussionSeroconversion occurred within 3 weeks after onset of symptoms with all assays and on average 2 days earlier for assays detecting IgG or total Ig anti-N than for IgG anti-S. The specificity of assays detecting anti-N was comparable to anti-S and excellent in a challenging control population.     

Antibody isotype epitope mapping of SARS-CoV-2 Spike RBD protein: Targets for COVID-19 symptomatology and disease control

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) still poses a challenge for biomedicine and public health. To advance the development of effective diagnostic, prognostic, and preventive interventions, our study focused on high-throughput antibody binding epitope mapping of the SARS-CoV-2 spike RBD protein by IgA, IgM and IgG antibodies in saliva and sera of different cohorts from healthy uninfected individuals to SARS-CoV-2-infected unvaccinated and vaccinated asymptomatic, recovered, nonsevere, and severe patients. Identified candidate diagnostic (455-LFRKSNLKPFERD-467), prognostic (395-VYADSFVIRGDEV-407-C-KLH, 332-ITNLCPFGEV-342-C-KLH, 352-AWNRKRI-358-C-KLH, 524-VCGPKKSTNLVKN-536-KLH), and protective (MKLLE-487-NCYFPLQSYGFQPTNGVG-504-GGGGS-446-GGNYNYLYRLFRKSNLKPFERD-467) epitopes were validated with sera from prevaccine and postvaccine cohorts. The results identified neutralizing epitopes and support that antibody recognition of linear B-cell epitopes in RBD protein is associated with antibody isotype and disease symptomatology. The findings in asymptomatic individuals suggest a role for anti-RBD antibodies in the protective response against SARS-CoV-2. The possibility of translating results into diagnostic interventions for the early diagnosis of asymptomatic individuals and prognosis of disease severity provides new tools for COVID-19 surveillance and evaluation of risks in hospitalized patients. These results, together with other approaches, may contribute to the development of new vaccines for the control of COVID-19 and other coronavirus-related diseases using a quantum vaccinomics approach through the combination of protective epitopes.     

人源化单链抗体与白细胞介素2融合蛋白靶向治疗肿瘤的实验研究

目的评价人源化抗Her2/neu单链抗体及人白细胞介素2(hIL-2)双功能融合蛋白H520C9scFv-hIL-2治疗Her2/neu阳性肿瘤的效果。方法将构建的表达载体转染293细胞,G418筛选阳性克隆建立稳定表达细胞系。免疫印迹法(Western blotting)、酶联免疫吸附试验(ELISA)及[3H]脱氧胸苷(3H-TdR)渗入法检测融合蛋白浓度和生物学活性。建立荷瘤小鼠肿瘤模型,静脉给药,观测肿瘤体积变化判断治疗效果。结果细胞培养上清中融合蛋白浓度达(1.2±0.23)mmol/L,5μl上清即可在46000处见到清晰蛋白条带。纯化后的融合蛋白两个功能单位活性良好,在荷瘤小鼠肿瘤模型治疗实验中显示了明确的治疗效果。结论哺乳动物细胞可高效表达生物活性良好的融合蛋白H520C9scFv-hIL-2,该蛋白在体内实验中有明显的抑瘤作用,显示了较好的应用前景。