Title: Ultrasensitive monitoring of SARS-CoV-2-specific antibody responses based on a digital approach reveals one week of IgG seroconversion

Journal: Biosens Bioelectron

Date: 2022/09/15

Abstract:

COVID-19 is still unfolding, while many people have been vaccinated. In comparison to nucleic acid testing (NAT), antibody-based immunoassays are faster and more convenient. However, its application has been hampered by its lower sensitivity and the existing fact that by traditional immunoassays, the measurable seroconversion time of pathogen-specific antibodies, such as IgM or IgG, lags far behind that of nucleic acids. Herein, by combining the single molecule array platform (Simoa), RBD, and a previously identified SARS-CoV-2 S2 protein derivatized 12-aa peptide (S2-78), we developed and optimized an ultrasensitive assay (UIM-COVID-19 assay). Sera collected from three sources were tested, i.e., convalescents, inactivated virus vaccine-immunized donors and wild-type authentic SARS-CoV-2-infected rhesus monkeys. The sensitivities of UIM-COVID-19 assays are 100-10,000 times higher than those of conventional flow cytometry, which is a relatively sensitive detection method at present. For the established UIM-COVID-19 assay using RBD as a probe, the IgG and IgM seroconversion times after vaccination were 7.5 and 8.6 days vs. 21.4 and 24 days for the flow cytometry assay, respectively. In addition, using S2-78 as a probe, the UIM-COVID-19 assay could differentiate COVID-19 patients (convalescents) from healthy people and patients with other diseases, with AUCs ranging from 0.85-0.95. In summary, the UIM-COVID-19 we developed here is a promising ultrasensitive biodetection strategy that has the potential to be applied for both immunological studies and diagnostics.

研究背景

COVID-19仍在发展，而许多人已经接种了疫苗。与核酸检测(NAT)相比，基于抗体的免疫测定更快、更方便。然而，其应用受到其敏感性较低以及传统免疫测定的已知事实的阻碍，即通过传统免疫测定，病原体特异性抗体(如IgM或IgG)的可测量血清转换时间远远落后于核酸。

研究方法

在本文中，通过将单分子阵列平台(Simoa)，RBD和先前鉴定的SARS-CoV-2 S2蛋白衍生化12-aa肽(S2-78)相结合，开发并优化了超灵敏测定(UIM-COVID-19测定)。

研究结果

测试了从三个来源收集的血清，即恢复期，灭活病毒疫苗免疫供体和野生型正宗SARS-CoV-2感染恒河猴。UIM-COVID-19检测的灵敏度比常规流式细胞术高100-10000倍，这是目前相对灵敏的检测方法。对于使用RBD作为探针的已建立的UIM-COVID-19测定，疫苗接种后的IgG和IgM血清转换时间分别为7.5天和8.6天，而流式细胞术测定的血清转换时间为21.4天和24天。此外，使用S2-78作为探针，UIM-COVID-19测定可以将COVID-19患者(恢复期患者)与健康人和患有其他疾病的患者区分开来，AUC范围为0.85-0.95。

研究结论

总之，我们在这里开发的UIM-COVID-19是一种有前途的超灵敏生物检测策略，有可能应用于免疫学研究和诊断。

参考文献

Ou F, et al. Ultrasensitive monitoring of SARS-CoV-2-specific antibody responses based on a digital approach reveals one week of IgG seroconversion. Biosens Bioelectron. 2022.