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. 2021 Aug 19:12:723585.
doi: 10.3389/fimmu.2021.723585. eCollection 2021.

Different Profiles of Antibodies and Cytokines Were Found Between Severe and Moderate COVID-19 Patients

Yaolin Guo  1 , Tianyi Li  1 , Xinyi Xia  2 , Bin Su  3 , Hanping Li  1 , Yingmei Feng  3 , Jingwan Han  1 , Xiaolin Wang  1 , Lei Jia  1 , Zuoyi Bao  1 , Jingyun Li  1 , Yongjian Liu  1 , Lin Li  1
Affiliations

Different Profiles of Antibodies and Cytokines Were Found Between Severe and Moderate COVID-19 Patients

Yaolin Guo et al. Front Immunol. .

Abstract

Objectives: Our objective was to determine the antibody and cytokine profiles in different COVID-19 patients.

Methods: COVID-19 patients with different clinical classifications were enrolled in this study. The level of IgG antibodies, IgA, IgM, IgE, and IgG subclasses targeting N and S proteins were tested using ELISA. Neutralizing antibody titers were determined by using a toxin neutralization assay (TNA) with live SARS-CoV-2. The concentrations of 8 cytokines, including IL-2, IL-4, IL-6, IL-10, CCL2, CXCL10, IFN-γ, and TNF-α, were measured using the Protein Sample Ella-Simple ELISA system. The differences in antibodies and cytokines between severe and moderate patients were compared by t-tests or Mann-Whitney tests.

Results: A total of 79 COVID-19 patients, including 49 moderate patients and 30 severe patients, were enrolled. Compared with those in moderate patients, neutralizing antibody and IgG-S antibody titers in severe patients were significantly higher. The concentration of IgG-N antibody was significantly higher than that of IgG-S antibody in COVID-19 patients. There was a significant difference in the distribution of IgG subclass antibodies between moderate patients and severe patients. The positive ratio of anti-S protein IgG3 is significantly more than anti-N protein IgG3, while the anti-S protein IgG4 positive rate is significantly less than the anti-N protein IgG4 positive rate. IL-2 was lower in COVID-19 patients than in healthy individuals, while IL-4, IL-6, CCL2, IFN-γ, and TNF-α were higher in COVID-19 patients than in healthy individuals. IL-6 was significantly higher in severe patients than in moderate patients. The antibody level of anti-S protein was positively correlated with the titer of neutralizing antibody, but there was no relationship between cytokines and neutralizing antibody.

Conclusions: Our findings show the severe COVID-19 patients' antibody levels were stronger than those of moderate patients, and a cytokine storm is associated with COVID-19 severity. There was a difference in immunoglobulin type between anti-S protein antibodies and anti-N protein antibodies in COVID-19 patients. And clarified the value of the profile in critical prevention.

Keywords: COVID-19; SARS-CoV-2; cytokine; immunoglobulin type; neutralizing antibody.

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Conflict of interest statement

The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

Figures

Figure 1
Figure 1
Comparison of relative quantitative nAb titers between the moderate and severe groups. (A) Average titers of neutralizing antibodies in moderate (n = 49) and severe (n = 30) patients. The box plots show the medians (middle line) and first and third quartiles (boxes), and the whiskers show the minimum and maximum. T-test P-values are depicted in the plots. (B, C) The percentage of moderate and severe patients with neutralizing antibody titers.
Figure 2
Figure 2
Comparison of IgG-S and IgG-N antibodies in the moderate (n = 49) and severe (n = 30) groups. The box plots show the medians (middle line) and first and third quartiles (boxes), and the whiskers show the minimum and maximum. Mann-Whitney test P-values are depicted in the plots. *p < 0.05, ****p < 0.0001.
Figure 3
Figure 3
The correlation between antibodies. The relationship between IgG-S and IgG-N antibody levels and nAb titers in moderate patients (A) and severe patients (B). The correlation between IgG-S antibody levels and nAb titers in moderate patients (C) and severe patients (D).
Figure 4
Figure 4
Classification of anti-S protein and anti-N protein antibodies. (A, B) The typing of anti-N protein immunoglobulin in moderate and severe patients. (C, D) The typing of anti-S protein immunoglobulin in moderate and severe patients. Samples with a fluorescence value greater than 0.2 were regarded as positive, with an assignment of 1; otherwise, they were regarded as negative, with an assignment of 0.
Figure 5
Figure 5
The comparison of cytokine concentrations between the healthy donor and moderate or severe groups. The unit of the eight cytokine concentrations was pg/mL. The box plots show the medians (middle line) and first and third quartiles (boxes), and the whiskers show the minimum and maximum. Mann-Whitney test P-values are depicted in the plots. I bars indicate standard deviations. **p < 0.01, ***p < 0.001, ****p < 0.0001.
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