Fast, high-throughput methods for measuring the level and duration of protective immune responses to SARS-CoV-2 are needed to anticipate the risk of breakthrough infections. Here we report the development of two quantitative PCR assays for SARS-CoV-2-specific T cell activation. The assays are rapid, internally normalized and probe-based: qTACT requires RNA extraction and dqTACT avoids sample preparation steps. Both assays rely on the quantification of CXCL10 messenger RNA, a chemokine whose expression is strongly correlated with activation of antigen-specific T cells. On restimulation of whole-blood cells with SARS-CoV-2 viral antigens, viral-specific T cells secrete IFN-γ, which stimulates monocytes to produce CXCL10. CXCL10 mRNA can thus serve as a proxy to quantify cellular immunity. Our assays may allow large-scale monitoring of the magnitude and duration of functional T cell immunity to SARS-CoV-2, thus helping to prioritize revaccination strategies in vulnerable populations.

需要快速、高通量的方法来测量针对 SARS-CoV-2 的保护性免疫反应的水平和持续时间，以预测突破性感染的风险。在此，我们报告了两种用于 SARS-CoV-2 特异性 T 细胞激活的定量 PCR 检测方法的开发。该检测快速、内部标准化且基于探针：qTACT 需要 RNA 提取，而 dqTACT 避免了样品制备步骤。两种检测均依赖于CXCL10信使 RNA 的定量，CXCL10 是一种趋化因子，其表达与抗原特异性 T 细胞的激活密切相关。用 SARS-CoV-2 病毒抗原重新刺激全血细胞时，病毒特异性 T 细胞会分泌 IFN-γ，刺激单核细胞产生CXCL10。因此， CXCL10 mRNA 可以作为量化细胞免疫的代理。我们的检测方法可以大规模监测针对 SARS-CoV-2 的功能性 T 细胞免疫的程度和持续时间，从而有助于优先考虑弱势群体的重新接种策略。