Department of Pathology and Laboratory Medicine, University of Colorado School of Medicine and Children's Hospital, Aurora, Colorado, USA.
Department of Immunology and Microbiology, University of Colorado School of Medicine, Aurora, Colorado, USA.
Transfusion. 2021 Apr;61(4):1148-1159. doi: 10.1111/trf.16261. Epub 2021 Jan 16.
In March 2020, the Food and Drug Administration (FDA) approved use of COVID-19 convalescent plasma (CCP) as an investigational new drug for treatment of COVID-19. Since then, collection of CCP from COVID-19-recovered patients has been implemented in donor centers nationwide. Children's Hospital Colorado rapidly put into practice a CCP collection protocol, necessitating development and implementation of assays to evaluate SARS-CoV-2 antibodies in CCP units.
We evaluated 87 units of CCP collected from 36 donors over two to four sequential donations using both antigen-binding assays for SARS-CoV-2 nucleoprotein and spike antigens and a live virus focus reduction neutralization test (FRNT ).
Our data show that the majority of donors (83%) had a FRNT titer of at least 80, and 61% had a titer of at least 160, which met the FDA's criteria for acceptable CCP units. Additionally, our data indicate that analysis of antibodies to a single SARS-CoV-2 antigen is likely to miss a percentage of seroconverters; however, these individuals tend to have neutralizing antibody titers of less than 80. There was considerable variability in the short-term, sustained antibody response, measured by neutralizing antibody titers, among our donor population.
The correlation of neutralizing activity and antigen-binding assays is necessary to qualify CCP for therapeutic use. Since SARS-CoV-2 antibody levels decline in a percentage of donors, and such a decline is not detectable by current qualitative assays implemented in many laboratories, robust, quantitative assays are necessary to evaluate CCP units best suited for therapeutic infusion in COVID-19 patients.
2020 年 3 月，美国食品和药物管理局（FDA）批准将 COVID-19 恢复期血浆（CCP）作为一种治疗 COVID-19 的研究性新药使用。此后，全国各地的捐赠中心都开始从 COVID-19 康复患者中采集 CCP。科罗拉多儿童医院迅速实施了 CCP 采集方案，这需要开发和实施检测试剂盒来评估 CCP 单位中的 SARS-CoV-2 抗体。
我们使用针对 SARS-CoV-2 核蛋白和刺突抗原的抗原结合检测试剂盒以及活病毒滴度降低中和试验（FRNT）评估了从 36 名捐赠者的 87 个 CCP 单位。
我们的数据显示，大多数捐赠者（83%）的 FRNT 滴度至少为 80，61%的滴度至少为 160，这符合 FDA 对可接受的 CCP 单位的标准。此外，我们的数据表明，对单个 SARS-CoV-2 抗原的抗体分析可能会错过一部分血清转换者；然而，这些个体的中和抗体滴度通常低于 80。在我们的供体人群中，通过中和抗体滴度测量的短期、持续抗体反应存在相当大的可变性。
为了将 CCP 定性为治疗用途，有必要对中和活性和抗原结合检测试剂盒进行相关性分析。由于 SARS-CoV-2 抗体水平在一定比例的供体中下降，而目前许多实验室实施的定性检测无法检测到这种下降，因此需要进行稳健的定量检测，以评估最适合 COVID-19 患者治疗输注的 CCP 单位。
