Abstract
Abstract Background There is a knowledge gap about the characteristics of neutralizing antibody (NAb) response in patients who recovered COVID-19. In this study, it is aimed to elucidate the factors affecting the presence and titers of antibodies up to 30-days after onset. Material and methods A total of 129 laboratory-confirmed COVID-19 patients were enrolled. Clinical data were obtained retrospectively. SARS-CoV-2 specific NAb, IgM, and IgG antibody responses were analyzed. Results SARS-CoV-2 specific NAb, IgM and IgG, were detected at the time of hospital discharge in 60.5%, 30.2%, and 51.9% of the patients, respectively. The median time for obtaining serum samples for antibody tests after symptoms’ onset was 11 days. The median titer of neutralizing antibody (SN50) was significantly higher in severe patients (25 vs. 7.5, p=0.009). Of the 23 severe patients, 52.2% (n=12) had higher NAb titers (i.e., SN50≥1:25) when compared to that in non-severe patients (OR=2.89; 95%CI=1.15–7.28, p=0.021), yet, the potential effect of follow-up time on NAb status and titers could not be ruled out. Conclusions The presence of antibody response is not the only determinative factor for recovery. The presence and higher titers of NAb were detected more in severe patients than their non-severe counterparts. Survival analysis suggested that this difference could at least be partially explained by the length of follow-up through antibody testing (at discharge) after symptoms’ onset.
Highlights
COVID-19 pandemic threatens global public health with heavy economic/social impacts
There are many questions to be explained, including the percentage of patients eliciting neutralizing antibody (NAb) after primary infection in protective titer, and whether there is a correlation between the clinical course of COVID-19 and the NAb response
We investigated IgM, IgG, and NAb response in sera of confirmed COVID-19 patients at the time of hospital discharge
Summary
The protective immune response elicited by primary infection is crucial to prevent re-infection. Limited information is available about the elicited protective immunity by SARS-CoV-2. In an animal study, acquired immunity due to primary infection with SARS-CoV-2 presented protection against subsequent infections [1]. Humoral antibodies in recovered COVID-19 patients have been reported, the titers were very low in some patients [2, 3]. Neutralizing antibodies (NAbs) are crucial components of protective immunity. The S-protein is the main determinant of SARS-CoV-2 infection, responsible for viral attachment, fusion, and entry into host cells [4]. Conventional virus-neutralizing assay (VNA) is the gold standard for determining NAbs [5]. There is a knowledge gap about the characteristics of neutralizing antibody (NAb) response in patients who recovered COVID-19. It is aimed to elucidate the factors affecting the presence and titers of antibodies up to 30-days after onset
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