PB1290 - The contribution of peptidylarginine deiminase 4 and NETs to a dysregulated VWF/ADAMTS13 axis in Staphylococcus aureus bacteremia in patients

Background: Neutrophils are key players in sepsis pathogenesis, with neutrophil extracellular traps (NETs) providing a thrombus scaffold that also binds von Willebrand factor (VWF). The enzyme peptidylarginine deiminase 4 (PAD4) is not only important for NET formation but also inactivates ADAMTS13. We hypothesized that inactivation of ADAMTS13 by PAD4 might occur in vivo in Gram-positive sepsis and contribute to clinical outcome.

Aims: To obtain clinical evidence of the balance between NETs/PAD4 and VWF/ADAMTS13 in systemic infection.

Methods: With appropriate ethical approval and informed consent, we collected plasma samples from hospitalized patients with Staphylococcus aureus bacteremia within 36 hours after bacteremia onset (n = 66, baseline), and 1 day (n = 58), 4 days (n = 49) and 7 days (n = 32) after enrollment. Samples were analyzed for PAD4, NET biomarkers, VWF antigen, and ADAMTS13 activity. Correlation analyses were performed using Spearman correlation with a two-sided significance level of 0.05.

Results: Despite low prevalence of severe sepsis, we found elevated levels of H3Cit (2.60 (1.56-4.57) ng/ml), MPO-DNA (8.32 (4.71-12.2) ng/ml), H3Cit-DNA (58.2 (40.4-91.4) ng/ml), PAD4 (1.61 (0.79-4.41 ng/ml), and VWF:Ag (3.07 (2.16-3.84 IU/ml), and decreased ADAMTS13 activity (50 (37.0-65.8) %) (median (IQR), values at baseline). Whereas C-reactive protein (CRP) decreased during longitudinal follow-up, PAD4, VWF, MPO-DNA, and H3Cit remained high. PAD4 antigen was negatively correlated with ADAMTS13 activity (r= -0.382, P=0.002), and H3Cit levels were positively correlated with VWF:Ag throughout the disease course. Baseline PAD4 levels were positively correlated with APACHE-II score, a predictor of mortality (r=0.322, P=0.009), and VWF was correlated with CRP (r=0.304, P=0.014 at baseline) and fibrinogen (r=0.344, P=0.015 at day 1).

Conclusion(s): We report elevated NETs and PAD4 in Gram-positive bacteremia, together with reduced ADAMTS13 activity. This supports the hypothesis that inactivation of ADAMTS13 by PAD4 occurs in systemic S. aureus infection, and may contribute to sepsis pathogenesis.