NET Biomarkers in COVID-19 and Post-COVID Syndrome: a Comprehensive Analysis, 2026, Monsalve et al.

[SNT Gatchaman]

NET Biomarkers in COVID-19 and Post-COVID Syndrome: a Comprehensive Analysis

Spoiler: Authors

Monsalve, Diana M; Numpaque-Morales, Laura; Rojas, Manuel; Acosta-Ampudia, Yeny; Ramírez-Santana, Carolina

SARS-CoV-2 triggers immune responses, including neutrophil activation and neutrophil extracellular trap (NET) release, contributing to COVID-19 severity. A significant proportion of patients experience persistent or new symptoms after recovery, referred to as post-COVID syndrome (PCS), which may be associated with NET release persistence. This study aimed to investigate whether NET-related biomarkers remain elevated after acute SARS-CoV-2 infection and to explore their association with PCS.

We conducted an analytical descriptive cohort study including patients with acute COVID-19 (n = 35), PCS (n = 35), and a pre-pandemic healthy control group (PPC; n = 35). Serum samples from participants were used to measure NET biomarkers, including MPO-DNA complexes, elastase-DNA complexes, and MPO levels. The capacity to induce NETosis in vitro was evaluated by incubating neutrophils with participant serum. Additionally, soluble immune markers, including cytokines, anti-SARS-CoV-2 antibodies, and autoantibodies, were assessed. A NETosis-based model was developed using NET biomarkers to distinguish between acute COVID-19 or PCS patients and PPC individuals.

Our findings revealed a significant increase in NET biomarkers during acute COVID-19 that persisted in PCS. This pattern was consistent with the in vitro study, where sera from PCS patients induced NET release. Additionally, NET biomarkers correlated with neutrophil counts, cytokines, autoantibodies, and inflammatory markers during acute COVID-19 and PCS. The multivariate model of NET biomarkers exhibited a high accuracy in distinguishing acute COVID-19 with an area under the curve (AUC) of 0.99 (CI = 0.98–1.00) and PCS patients with an AUC of 0.91 (CI = 0.84–0.99) from PPC.

These findings suggest that persistent NETosis may contribute to PCS pathophysiology, highlighting NETs as potential biomarkers and therapeutic targets in post-viral syndromes.

Web | DOI | PDF | Journal of Clinical Immunology | Open Access

 

[SNT Gatchaman]

Sera from the acute COVID-19 group showed a trend toward increased NET formation compared with PPC, although this difference did not reach statistical significance. In contrast, sera from the PCS group significantly induced NET formation compared with PPC (p=0.0334) (Fig. 2A, B). These findings indicate that PCS serum retains the NET-inducing potential observed during acute infection.

(PMA is a positive control.)

Additionally, the presence of NETs was verified by ELISA quantification of MPO-DNA complexes and MPO levels in the supernatants. MPO-DNA complex levels were significantly higher in acute COVID-19 (p=0.0035) and PCS (p=0.0498) compared with PPC. In contrast, MPO levels were significantly increased only in PCS (p=0.0173). No significant differences were found between acute COVID-19 and PCS (Fig. 2, C and D).

 

[Jonathan Edwards]

But I see no evidence for NETs actually being present in PCS.
Maybe the 'markers' don't necessarily mark NETS.

 

[Jonathan Edwards]

40% of PCS cases had rheumatoid factor, with 3% controls, which they make no mention of later as far as i can see. That is an odd result.

But I think it was done in a rheumatology unit.

 

[Hutan]

No convalescent controls?

Edit to add: 35 people in the acute-Covid-19 (hospitalised) +

Thirty-five individuals with confirmed PCS and available serum samples from the acute phase were included in the study. These patients voluntarily attended the post-COVID unit. Participants with a history of SARS-CoV-2 vaccination, preexisting autoimmune diseases prior to acute infection, or without laboratory-confirmed COVID-19 were excluded [8].

For the PPC group, individuals were selected based on the absence of autoimmune diseases and no prior exposure to SARS-CoV-2. Additionally, neutrophil purification assays were performed using samples from five healthy post-pandemic volunteers.