Abstract：
During SARS-CoV-2 pandemic, the assessment of immune protection of people at risk of severe infection was an important goal. The appearance of VOCs (Variant of Concern) highlighted the limits of evaluating immune protection through the humoral response. While the humoral response partly loses its neutralizing activity, the anti-SARS-CoV-2 memory T cell response strongly cross protects against VOCs becoming an indispensable tool to assess immune protection. We compared two techniques available in laboratory to evaluate anti-SARS-CoV-2 memory T cell response in a cohort of infected or vaccinated patients with different levels of risk to develop a severe disease: the ELISpot assay and the T-Cell Lymphocyte Proliferation Assay respectively exploring IFNγ production and cell proliferation. We showed that the ELISpot assay detected more anti-Spike memory T cell response than the Lymphocyte Proliferation Assay. We next observed that the use of two different suppliers as antigenic source in the ELISpot assay did not affect the detection of anti-Spike memory T cell response. Finally, we explored a new approach for defining the positivity threshold, using unsupervised mixed Gaussian modeling, challenging the traditional ROC curve used by the supplier. That will be helpful in endemic situation where it could be difficult to recruit \"negative\" patients.
摘要：
在SARS-CoV-2大流行期间，对有严重感染风险的人群进行免疫保护评估是一项重要目标.VOC（关注变体）的出现强调了通过体液反应评估免疫保护的局限性。虽然体液反应部分失去了它的中和活性，抗SARS-CoV-2记忆T细胞反应强烈交叉保护免受VOC的侵害成为评估免疫保护的不可或缺的工具。我们比较了实验室可用的两种技术，以评估一组感染或接种疫苗的患者中的抗SARS-CoV-2记忆T细胞反应，这些患者具有不同程度的严重疾病的风险：ELISpot测定法和T细胞淋巴细胞增殖测定法分别探索IFNγ的产生和细胞增殖。我们表明，与淋巴细胞增殖测定相比，ELISpot测定检测到更多的抗刺突记忆T细胞反应。我们接下来观察到,在ELISpot测定中使用两个不同的供应商作为抗原来源不影响抗-Spike记忆T细胞应答的检测。最后,我们探索了一种定义积极性阈值的新方法，使用无监督混合高斯建模，挑战供应商使用的传统ROC曲线。这将有助于在很难招募“阴性”患者的地方性情况。
