Elevated plasma levels of selective cytokines in COVID-19 patients reflect viral load and lung injury

Abstract

A recent outbreak of pneumonia in Wuhan, China was found to be caused by a 2019 novel coronavirus (2019-nCoV or SARS-CoV-2 or HCoV-19). We previously reported the clinical features of 12 patients with 2019-nCoV infections in Shenzhen, China. To further understand the pathogenesis of COVID-19 and find better ways to monitor and treat the disease caused by 2019-nCoV, we measured the levels of 48 cytokines in the blood plasma of those 12 COVID-19 patients. Thirty-eight out of the 48 measured cytokines in the plasma of 2019-nCoV-infected patients were significantly elevated compared to healthy individuals. Seventeen cytokines were linked to 2019-nCoV loads. Fifteen cytokines, namely M-CSF, IL-10, IFN-α2, IL-17, IL-4, IP-10, IL-7, IL-1ra, G-CSF, IL-12, IFN-γ, IL-1α, IL-2, HGF and PDGF-BB, were strongly associated with the lung-injury Murray score and could be used to predict the disease severity of 2019-nCoV infections by calculating the area under the curve of the receiver-operating characteristics. Our results suggest that 2019-nCoV infections trigger extensive changes in a wide array of cytokines, some of which could be potential biomarkers of disease severity of 2019-nCoV infections. These findings will likely improve our understanding of the immunopathologic mechanisms of this emerging disease. Our results also suggest that modulators of cytokine responses may play a therapeutic role in combating the disease once the functions of these elevated cytokines have been characterized.

Keywords: 2019-nCoV; COVID-19; IL-17; IP-10; cytokine storm.

Figure 1.

Correlation between cytokine plasma levels and viral Ct value in patients with 2019-nCoV infections. The plasma levels of cytokines (M-CSF, IL-10, IFN-α2, IL-13, IL-17, IL-4, IP-10, IL-1β, IL-7, IL-1ra, G-CSF, IL-12 (p40), IFN-γ, IL-1α, IL-2, HGF and PDGF-BB) were measured in a total of 25 blood samples from 12 patients with 2019-nCoV infections. The viral titers were detected in 18 samples from 10 patients infected with 2019-nCoV. Spearman's rank correlation analysis (r) was used for linear-correlation analysis.

Figure 2.

Murray score highly correlates with plasma cytokine levels in patients with 2019-nCoV infections. The plasma levels of cytokines (IL-12, IFN-γ, IL-2, HGF, IFN-α2, IL-4, IL-17, IP-10, G-CSF, IL-10, IL-1ra, M-CSF, IL-1α, IL-7 and PDGF-BB) were measured in a total of 25 blood samples from 12 patients with 2019-nCoV infections. Clinical indicators from the same day as the blood-sample collection were used to calculate the Murray score (an indicator of lung-injury severity). Spearman's rank correlation analysis (r) was used for linear-correlation analysis.

Figure 3.

The ROC curve of plasma cytokine levels for patients with mild and severe 2019-nCoV-infections. The area under the receiver-operating characteristic (ROC) curve (AUC) of the plasma cytokine levels (IL-12, IL-1ra, IP-10, PDGF-BB, IFN-α2, IFN-γ, M-CSF, IL-17, HGF, G-CSF, IL-2, IL-4, IL-10, IL-1α and IL-7) was estimated in 8 samples from 4 mild COVID-19 (COVID-19-M) patients and 17 samples from 8 severe COVID-19 (COVID-19-S) patients. The P-values of all AUC for plasma cytokine levels were <0.05.

Figure 4.

Plasma cytokine levels in healthy controls, severe bacteria pneumonia patients, H7N9-infected patients and 2019-nCoV-infected patients. The plasma levels of cytokines (M-CSF, IL-10, IFN-α2, IL-17, IL-4, IP-10, IL-7, IL-1ra, G-CSF, IL-12 (p40), IFN-γ, IL-1α, IL-2, HGF and PDGF-BB) were measured in 8 samples from 8 healthy controls, 8 samples from 8 severe bacteria pneumonia patients, 8 samples from 8 H7N9-infected patients, 8 samples from 4 2019-nCoV-infected patients with mild illness (COVID-19-M) and 17 samples from 8 patients with severe illness (COVID-19-S). Detailed information is shown in Supplementary Table 2. *P < 0.05; ^**P < 0.01; ^***P < 0.001.