For the assessment of vaccine-induced immune response and to understand the role of antibodies in neutralization, it is necessary to assess dynamics of various antibodies in patients with different clinical manifestations. This study aims to quantitate circulating levels of IgA/IgG and IgG subtypes induced at different days postonset of symptoms, in severe and nonsevere patients. For this, serum or plasma samples (n = 146) collected from 79 COVID-19 patients were used. Indirect severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) specific IgA, IgG, and IgG subtype specific enzyme-linked immunosorbent assays (ELISAs) were performed. Antibody titers between severe and nonsevere patients were compared at different times postonset of clinical symptoms. Titers in ELISA were compared to neutralizing antibody (Nab) titers determined by plaque reduction neutralization test (PRNT). Over 75% patients were positive for IgA/IgG antibodies in the first week. The ELISA titers did not differ during the first week; however, severe disease exhibited raised titers thereafter. Nab titers correlated with the ELISA titers in mild presentation but not in severe disease. IgA and IgG1 antibodies correlated stronger with Nabs. The findings highlighted that IgA together with IgG play an important in SARS-CoV-2 neutralization. These results will prove useful in assessing efficacy of vaccines and understanding disease pathogenesis.

中文翻译：

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严重和非严重COVID-19患者对SARS-CoV-2的抗体（IgA，IgG和IgG亚型）反应

为了评估疫苗诱导的免疫反应并了解抗体在中和中的作用，有必要评估具有不同临床表现的患者中各种抗体的动力学。这项研究的目的是量化严重和不严重患者在症状发作后不同天诱导的IgA / IgG和IgG亚型的循环水平。为此，血清或血浆样品（n = 146）使用了从79名COVID-19患者中收集的数据。进行了间接严重急性呼吸综合征冠状病毒2（SARS-CoV-2）特异性IgA，IgG和IgG亚型特异性酶联免疫吸附测定（ELISAs）。在临床症状发作后的不同时间比较了严重和不严重患者之间的抗体滴度。将ELISA中的滴度与通过噬斑减少中和试验（PRNT）确定的中和抗体（Nab）滴度进行比较。在第一周，超过75％的患者IgA / IgG抗体呈阳性。第一周的ELISA滴度没有变化。但是，严重的疾病此后显示出更高的滴度。在轻度表现中，Nab滴度与ELISA滴度相关，而在严重疾病中则不相关。IgA和IgG1抗体与Nabs相关性更强。研究结果强调，IgA与IgG一起在SARS-CoV-2中和中起重要作用。这些结果将证明对评估疫苗的效力和了解疾病的发病机理很有用。