Increased plasma level of soluble P-selectin in non-hospitalized COVID-19 convalescent donors

Abstract

Background: The coronavirus disease-2019 (COVID-19) is a systemic disease with severe implications on the vascular and coagulation system. A procoagulant platelet phenotype has been reported at least in the acute disease phase. Soluble P-selectin (sP-sel) in the plasma is a surrogate biomarker of platelet activation. Increased plasma levels of sP-sel have been reported in hospitalized COVID-19 patients associated with disease severity. Here, we evaluated in a longitudinal study the sP-sel plasma concentration in blood donors who previously suffered from moderate COVID-19.

Methods: 154 COVID-19 convalescent and 111 non-infected control donors were recruited for plasma donation and for participation in the CORE research trial. First donation (T1) was performed 43-378 days after COVID-19 diagnosis. From most of the donors the second (T2) plasma donation including blood sampling was obtained after a time period of 21-74 days and the third (T3) donation after additional 22-78 days. Baseline characteristics including COVID-19 symptoms of the donors were recorded based on a questionnaire. Platelet function was measured at T1 by flow cytometry and light transmission aggregometry in a representative subgroup of 25 COVID-19 convalescent and 28 control donors. The sP-sel plasma concentration was determined in a total of 704 samples by using a commercial ELISA.

Results: In vitro platelet function was comparable in COVID-19 convalescent and control donors at T1. Plasma samples from COVID-19 convalescent donors revealed a significantly higher sP-sel level compared to controls at T1 (1.05 ± 0.42 ng/mL vs. 0.81 ± 0.30 ng/mL; p < 0.0001) and T2 (0.96 ± 0.39 ng/mL vs. 0.83 ± 0.38 ng/mL; p = 0.0098). At T3 the sP-sel plasma level was comparable in both study groups. Most of the COVID-19 convalescent donors showed a continuous decrease of sP-sel from T1 to T3.

Conclusion: Increased sP-sel plasma concentration as a marker for platelet or endothelial activation could be demonstrated even weeks after moderate COVID-19, whereas, in vitro platelet function was comparable with non-infected controls. We conclude that COVID-19 and additional individual factors could lead to an increase of the sP-sel plasma level.

Keywords: CD62P; COVID-19; Plasma marker; Platelet function; SARS-CoV-2 infection; Soluble P-selectin.

Fig. 1

Plasma level of soluble P-selectin (sP-sel) in COVID-19 convalescent donors (gray boxes) and control donors (HC; white boxes) determined in blood samples taken at up to 3 time points (T1, T2, T3). The median time period (days, d) between T1 and T2 and between T2 and T3 is indicated. The numbers of analyzed blood samples from COVID and control donors at the 3 time points are given.

Fig. 2

Course of the sP-sel plasma level in 59 COVID-19 convalescent donors with sP-sel higher than the median (>0.93 ng/mL) of all convalescent donors at T1. In the majority of the donors sP-sel continuously decreased from T1 to T2 (after 43 days) and from T2 to T3 (after 42 days). Seven donors (black lines) showed higher sP-sel at T3 compared to T1. The median of sP-sel in the 59 donors is indicated by the dashed line.