Rapid tests to evaluate severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2)-specific T-cell responses are urgently needed to decipher protective immunity and aid monitoring vaccine-induced immunity.

Using a rapid whole blood assay requiring a minimal amount of blood, we measured qualitatively and quantitatively SARS-CoV-2-specific CD4 T-cell responses in 31 healthcare workers using flow cytometry.

100% of COVID-19 convalescent participants displayed a detectable SARS-CoV-2-specific CD4 T-cell response. SARS-CoV-2-responding cells were also detected in 40.9% of participants with no COVID-19-associated symptoms or who tested PCR-negative. Phenotypic assessment indicated that, in COVID-19 convalescent participants, SARS-CoV-2 CD4 responses displayed an early differentiated memory phenotype with limited capacity to produce interferon (IFN)-. Conversely, in participants with no reported symptoms, SARS-CoV-2 CD4 responses were enriched in late differentiated cells, coexpressing IFN- and tumour necrosis factor-α and also Granzyme B.

This proof-of-concept study presents a scalable alternative to peripheral blood mononuclear cell-based assays to enumerate and phenotype SARS-CoV-2-responding T-cells, thus representing a practical tool to monitor adaptive immunity due to natural infection or vaccine trials.

迫切需要快速测试来评估严重急性呼吸综合征冠状病毒 2 (SARS-CoV-2) 特异性 T 细胞反应，以破译保护性免疫并帮助监测疫苗诱导的免疫。

我们使用需要最少量血液的快速全血检测，使用流式细胞术定性和定量测量了 31 名医护人员的 SARS-CoV-2 特异性 CD4 T 细胞反应。

100% 的 COVID-19 康复期参与者表现出可检测到的 SARS-CoV-2 特异性 CD4 T 细胞反应。在 40.9% 没有 COVID-19 相关症状或 PCR 检测呈阴性的参与者中也检测到了 SARS-CoV-2 反应细胞。表型评估表明，在 COVID-19 恢复期参与者中，SARS-CoV-2 CD4 反应表现出早期分化的记忆表型，产生干扰素 (IFN) 的能力有限。相反，在没有报告症状的参与者中，SARS-CoV-2 CD4 反应在晚期分化细胞中丰富，共表达 IFN-和肿瘤坏死因子-α 以及粒酶 B。

这项概念验证研究提出了一种可扩展的替代基于外周血单核细胞的检测方法，用于对 SARS-CoV-2 反应的 T 细胞进行计数和表型分析，从而成为监测自然感染或疫苗试验引起的适应性免疫的实用工具。