Plasma markers of COVID-19 severity: a pilot study

Abstract

Background: SARS-CoV-2 infected patients show heterogeneous clinical presentations ranging from mild symptoms to severe respiratory failure and death. Consequently, various markers reflect this wide spectrum of disease presentations.

Methods: Our pilot cohort included moderate (n = 10) and severe (n = 10) COVID-19 patients, and 10 healthy controls. We determined plasma levels of nine acute phase proteins (APPs) by nephelometry, and full-length (M65), caspase-cleaved (M30) cytokeratin 18, and ADAMTS13 (a disintegrin-like and metalloprotease with thrombospondin type-1 motif 13) by ELISA. In addition, we examined whole plasma N-glycosylation by capillary gel electrophoresis coupled to laser-induced fluorescence detection (CGE-LIF).

Results: When compared to controls, COVID-19 patients had significantly lower concentrations of ADAMTS13 and albumin (ALB) but higher M30, M65, α1-acid glycoprotein (AGP), α1-antitrypsin (AAT), ceruloplasmin (CP), haptoglobin (HP), and high-sensitivity C-reactive protein (hs-CRP). The concentrations of α1-antichymotrypsin (ACT), α2-macroglobulin (A2MG) and serum amyloid A (SAA) proteins did not differ. We found significantly higher levels of AAT and M65 but lower ALB in severe compared to moderate COVID-19 patients. N-glycan analysis of the serum proteome revealed increased levels of oligomannose- and sialylated di-antennary glycans and decreased non-sialylated di-antennary glycan A2G2 in COVID-19 patients compared to controls.

Conclusions: COVID-19-associated changes in levels and N-glycosylation of specific plasma proteins highlight complexity of inflammatory process and grant further investigations.

Keywords: Acute phase proteins; COVID-9 severity; Cell death; Inflammation; N-glycosylation; Trombosis.

Fig. 1

Cell death (M65) and apoptosis (M30) markers in COVID-19 patients with different disease severities: A Plasma levels of M30 were measured in 10 severely and 10 moderately ill COVID-19 patients as well as in 10 healthy controls. Values are given as median (IQR). P-values were calculated by Kruskal–Wallis test and Dunn’s multiple comparison test. B Plasma levels of M65 were measured in 10 severely and 10 moderately ill COVID-19 patients as well as in 10 healthy controls. Values are given as mean (SD). P-values were calculated by one-way ANOVA test. A p-value below 0.05 was considered significant

Fig. 2

Thrombosis marker ADAMTS13 in COVID-19 patients with different disease severities: Plasma levels of ADAMTS13 were measured in 10 severely and 10 moderately ill COVID-19 patients as well as in 10 healthy controls. Values are given as median (IQR). P-values were calculated by Kruskal–Wallis test and Dunn’s multiple comparison test. A p-value below 0.05 was considered a significant

Fig. 3

N-glycan profiling of whole serum proteins revealed changes in glycosylation state during COVID-19 infection. Box plot display relative signal intensities of whole-serum derived N-glycans of moderate COVID-19 patients, severe-COVID-19 patients, and healthy controls (n = 10, each). Assigned N-glycans are depicted as pictograms with purple diamond: sialic acid; yellow circle: galactose; blue square: N-acetylglucosamine; green circle: mannose, red triangle: fucose; blue circle: glucose. Symbolic representation of pictograms follows the guidelines of Symbol Nomenclature for Glycans (SNFG) [29]. Student’s t-test two-sided: one star (*) indicate a p-value < 0.05, two stars (**) indicate a p-value < 0.01, and three stars (***) indicate a p-value < 0.001 based on less significant differences when comparing control and each COVID-19 group