While the antibody response to SARS-CoV-2 has been extensively studied in blood, relatively little is known about the antibody response in saliva and its relationship to systemic antibody levels. Here, we profiled by enzyme-linked immunosorbent assays (ELISAs) IgG, IgA and IgM responses to the SARS-CoV-2 spike protein (full length trimer) and its receptor-binding domain (RBD) in serum and saliva of acute and convalescent patients with laboratory-diagnosed COVID-19 ranging from 3–115 days post-symptom onset (PSO), compared to negative controls. Anti-SARS-CoV-2 antibody responses were readily detected in serum and saliva, with peak IgG levels attained by 16–30 days PSO. Longitudinal analysis revealed that anti-SARS-CoV-2 IgA and IgM antibodies rapidly decayed, while IgG antibodies remained relatively stable up to 105 days PSO in both biofluids. Lastly, IgG, IgM and to a lesser extent IgA responses to spike and RBD in the serum positively correlated with matched saliva samples. This study confirms that serum and saliva IgG antibodies to SARS-CoV-2 are maintained in the majority of COVID-19 patients for at least 3 months PSO. IgG responses in saliva may serve as a surrogate measure of systemic immunity to SARS-CoV-2 based on their correlation with serum IgG responses.

虽然在血液中对 SARS-CoV-2 的抗体反应进行了广泛的研究，但对唾液中的抗体反应及其与全身抗体水平的关系知之甚少。在这里，我们通过酶联免疫吸附试验 (ELISA) 分析了急性和恢复期患者血清和唾液中对 SARS-CoV-2 刺突蛋白（全长三聚体）及其受体结合域 (RBD) 的 IgG、IgA 和 IgM 反应。与阴性对照相比，实验室诊断出的 COVID-19 患者在症状发作后 (PSO) 3-115 天不等。在血清和唾液中很容易检测到抗 SARS-CoV-2 抗体反应，在 16-30 天 PSO 时达到峰值 IgG 水平。纵向分析显示，抗 SARS-CoV-2 IgA 和 IgM 抗体迅速衰减，而 IgG 抗体在两种生物体液中保持相对稳定长达 105 天的 PSO。最后，IgG、IgM 和在较小程度上对血清中的尖峰和 RBD 的 IgA 反应与匹配的唾液样本呈正相关。该研究证实，针对 SARS-CoV-2 的血清和唾液 IgG 抗体在大多数 COVID-19 患者中保持至少 3 个月 PSO。根据唾液中的 IgG 反应与血清 IgG 反应的相关性，唾液中的 IgG 反应可以作为对 SARS-CoV-2 全身免疫的替代指标。