Abstract
Clinical and Immune response characteristics of COVID-19 between severe and non-severe patients have not been fully clarified. In this study, clinical features, antibody responses targeting SARS-CoV-2 spike protein (S) and its different domains, Ig isotypes and IgG subtypes, ACE2 competitive antibodies, binding titers with FcγIIa and FcγIIb receptors, and 14 cytokines were investigated in 119 serum samples from 37 PCR-confirmed COVID-19 patients. Severe group including 9 patients represented lower lymphocyte count, higher neutrophil count, higher level of LDH, total bile acid (TBA) (P<1×10-4), r-glutaminase (P=0.011), adenosine deaminase (P<1×10-4), procalcitonin (P=0.004), C-reactive protein (P<1×10-4) and D-dimer (P=0.049) compared to non-severe group (28 patients). Significantly, higher-level antibody targeting S (IgA, IgM, and IgG), different S domains specificity (RBD, RBM, NTD, and CTD), FcγIIa and FcγIIb binding capability were observed in severe group than that of non-severe group, of which IgG1 and IgG3 were the main IgG subclasses. RBD-IgG were strongly correlated with S-IgG both in severe group and non-severe group. Additionally, CTD-IgG were strongly correlated with S-IgG in non-severe group. Positive RBD-ACE2 binding inhibition was strongly associated with high titers of antibody (S-IgG1, S-IgG3, NTD-IgG) especially RBD-IgG and CTD-IgG in severe group, while in non-severe group, S-IgG3, RBD-IgG and NTD-IgG titer correlated with ACE2 blocking rate. S-IgG1 was negatively associated with illness days in severe group (r=- 0.434, P=0.002), while S-IgG3 in severe group (r=0.363, P=0.011) and S-IgG1 (r=0.417, P=3×10-4) in non-severe group was positively associated with days after symptom onset. Moreover, GRO-α, IL-6, IL-8, IP-10, MCP-1, MCP-3, MIG, and BAFF were also significantly elevated in severe group. Overall, the results indicated different signatures in clinical and immune responses between the COVID-19 severe group and non-severe group, which will be markedly contributed to future therapeutic and preventive measures development.