High throughput serological tests that can establish the presence and functional activity of anti-SARS-COV2 antibodies are urgently needed. Here we present microsphere-based Flow Cytometry assays that quantify both anti-spike IgGs in plasma, and the ability of plasma to inhibit the binding of spike protein to angiotensin converting enzyme 2 (ACE2). First, we detected anti-trimer IgGs in 22/24 and anti-RBD IgGs in 21/24 COVID+ subjects at a median of 36 (range 14-73) days following documented SARS-CoV-2 RNA (+) secretions. Next, we find that plasma from all 22/24 subjects with anti-trimer IgGs inhibited ACE2-trimer binding to a greater degree than controls, and that the degree of inhibition correlated with anti-trimer IgG levels. Depletion of trimer-reactive Igs from plasma reduced ACE2-trimer inhibitory capacity to a greater degree than depletion of RBD-reactive Igs, suggesting that inhibitory antibodies act by binding both within and outside of the RBD. Amongst the 24 subjects, presence of fever was associated with higher levels of anti-trimer IgG and inhibition of binding to human ACE2. This inhibition assay may be broadly useful to quantify the functional antibody response of recovered COVID19 patients or vaccine recipients in a cell-free assay system.

中文翻译：

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在基于微球的抑制试验中，来自回收的COVID19受试者的血浆抑制刺突蛋白与ACE2的结合。

迫切需要能够确定抗SARS-COV2抗体的存在和功能活性的高通量血清学测试。在这里，我们介绍了基于微球的流式细胞术，可量化血浆中的抗尖峰IgG和血浆抑制尖峰蛋白与血管紧张素转化酶2（ACE2）结合的能力。首先，在记录SARS-CoV-2 RNA（+）分泌后的中位数36天（14-73天）内，我们在22/24个COVID +受试者中检测了抗三聚体IgG，在21/24个COVID +受试者中检测了抗RBD IgG。接下来，我们发现来自所有具有抗三聚体IgG的22/24受试者的血浆抑制ACE2-三聚体的结合程度大于对照，并且抑制程度与抗三聚体IgG水平相关。血浆中三聚体反应性Ig的消耗比RBD反应性Igs的消耗更大程度地降低了ACE2-三聚体的抑制能力，这表明抑制性抗体通过结合RBD内部和外部发挥作用。在24名受试者中，发烧与抗三聚体IgG水平升高和与人ACE2结合的抑制有关。这种抑制分析可广泛用于定量无细胞分析系统中回收的COVID19患者或疫苗接种者的功能抗体反应。