SARS-CoV-2特异性抗体ADCC活性与抗体滴度和中和活性呈正相关

SARS-CoV-2-specific antibody-dependent cell-mediated cytotoxicity positively correlated with antibody titer and neutralizing activity

目的:探讨SARS-CoV-2感染者血浆样本抗体依赖细胞介导的细胞毒作用(antibody-dependent cell-mediated cytotoxicity,ADCC)及其与抗体滴度和中和活性的相关性。方法:采用表达SARS-CoV-2刺突(spike;S)蛋白的HEK293T细胞为靶细胞,表达FcγRⅢa-V158的Jurkat细胞为效应细胞,建立一种简便的抗体ADCC检测方法。对效应细胞和靶细胞比例进行优化后,分析38份血浆样本的ADCC活性进行。血浆特异性抗体采用捕获ELISA法检测,即用抗标签抗体捕获C-端带标签的重组SARS-CoV-2 S蛋白。血浆抗体中和活性采用假病毒中和试验测定。统计学分析使用Mann-Whitney U检验进行组间比较,非参数Spearman相关检验计算相关性。结果:特异性抗体检测结果显示,38份血浆样本S、S1和受体结合结构域(receptor-binding domain,RBD)抗体阳转率均为97.4%(37/38);动态观察抗体滴度随康复时间的变化趋势,结果显示抗体滴度在3~4周达到峰值。抗体滴度>1∶320的血浆样本的中和活性高于抗体滴度<1∶320的血浆样本[IC 50值:749.6(396.5~3772.0)vs 81.4(11.6~228.4),P<0.01]。对同样的样本进行抗体ADCC活性检测,86.8%(33/38)的血浆样本可检测出ADCC活性,其随康复时间的变化趋势与特异性抗体滴度是一致的,同样在3~4周达到峰值。进一步分析抗体ADCC活性与抗体滴度和中和活性相关性,结果显示均呈正相关,针对S、S1和RBD三个不同靶向区域的抗体,其相关系数分别为0.686、0.535、0.471(P均<0.01),与中和活性的相关系数为0.573(P<0.01)。结论:本研究提供了一种简便的抗体ADCC检测方法,检测结果表明SARS-CoV-2可诱导特异性血浆抗体ADCC活性,且ADCC活性可能来自非中和抗体。同时,ADCC活性在3~4周达到峰值,这些发现为临床血浆救治提供了参考。

Objective To investigate the antibody-dependent cell-mediated cytotoxicity(ADCC)in plasma samples from patients with SARS-CoV-2 infection and to evaluate its correlation with antibody titer and neutralizing activity.Methods A simple method for ADCC detection was established using HEK293T cells expressing SARS-CoV-2 spike(S)protein as target cells and FcγRⅢa-V158-expressing Jurkat cells as effector cells.It was used to analyze the ADCC activity in 38 plasma samples after the ratio of effector cells to target cells was optimized.Plasma-specific antibody was detected by capturing ELISA,which was to capture the C-terminal-tagged recombinant SARS-CoV-2 S protein with an anti-tag antibody.The neutralizing activity in plasma samples was detected using a pseudovirus neutralization assay.Mann-Whitney U test was used for comparison between different groups and non-parametric Spearman correlation test was performed for correlation analysis.Results The seroconversion rates for antibodies specific for S protein,S1 protein and RBD were all 97.4%(37/38),and the dynamic changes in antibody titers with recovery time showed that antibody titers peaked at 3-4 weeks.Among the plasma samples with neutralizing activity,those with antibody titers>1∶320 had stronger neutralizing activity than the plasma samples with antibody titers<1∶320[IC50:749.6(396.5-3772.0)vs 81.4(11.6-228.4),P<0.01].ADCC activity was detectable in 86.8%(33/38)of the plasma samples,and its dynamic change with recovery time were consistent with that of specific antibody titer with a peak at 3-4 weeks.Correlation analysis showed ADCC was positively correlated with the titers of antibodies specific for S protein,S1 protein and RBD(r=0.686,0.535 and 0.471,all P<0.01).A positive correlation was also found between ADCC and neutralizing activity(r=0.573,P<0.01).Conclusions This study established a simple method for the detection of ADCC.Results of this study suggested that SARS-CoV-2 could induce specific ADCC in plasma and the ADCC might be associated with non-neutralizing antibodies.Besides,the activity of ADCC peaked at 3-4 weeks.These findings would be of reference value for clinical treatment with convalescent plasma.