Background: Pre-existing antibody reactivity against SARS-CoV-2 in unexposed people is a potentially important consideration for COVID-19 severity and vaccine responses. However, it has been difficult to quantify due to a lack of reliable defined background titers in unexposed individuals.

Methods: We measured IgG against multiple SARS-CoV-2 antigens, SARS-CoV and other circulating coronavirus spike proteins using a highly sensitive multiplex assay, and total SARS-CoV-2 spike-specific antibodies (IgG/M/A) using a commercial CLIA assay in 276 adults from the Vancouver area, Canada between May 17th and June 19th 2020. Reactivity threshold in unexposed individuals were defined comparing to pre-pandemic sera and to sera from infants under 6 months of age.

Results: The seroprevalence from a SARS-CoV-2 exposure, adjusted for false-positive and false-negative test results, was 0.60% in our adult cohort. High antibody reactivity to circulating endemic coronaviruses was observed in all adults and was about 10-fold lower in infants under 6 months. Consistent with a waning of maternal antibodies, reactivity in infants decreased more than 50-fold eight months later. SARS-CoV-2 Spike, RBD, NTD or nucleocapsid antibody reactivity >100-fold above that of older infants was detected in the vast majority of unexposed adults and pre-pandemic sera. This antibody reactivity correlated with titers against circulating coronaviruses, but not with age, sex, or whether adults were healthcare workers.

Conclusion: A majority of unexposed adults have pre-existing antibody reactivity against SARS-CoV-2. The lack of similar antibody reactivity in infants where maternal antibodies have waned suggests that this cross-reactivity is acquired, likely from repeated exposures to circulating coronaviruses.

---

 

乐备实是国内专注于提供高质量蛋白检测以及组学分析服务的实验服务专家，自2018年成立以来，乐备实不断寻求突破，公司的服务技术平台已扩展到单细胞测序、空间多组学、流式检测、超敏电化学发光、Luminex多因子检测、抗体芯片、PCR Array、ELISA、Elispot、PLA蛋白互作、多色免疫组化、DSP空间多组学等30多个，建立起了一套涵盖基因、蛋白、细胞以及组织水平实验的完整检测体系。

 
我们可提供从样本运输、储存管理、样本制备、样本检测到检测数据分析的全流程服务。凭借严格的实验室管理流程、标准化实验室操作、原始数据储存体系以及实验项目管理系统，已经为超过3000家客户单位提供服务，年检测样本超过100万，受到了广大客户的信任与支持。