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Baillie K, Davies HE, Keat SBK, Ladell K, Miners KL, Jones SA, Mellou E, Toonen EJM, Price DA, Morgan BP, Zelek WM. Complement dysregulation is a prevalent and therapeutically amenable feature of long COVID. Med 2024; 5:239-253.e5. [PMID: 38359836 DOI: 10.1016/j.medj.2024.01.011] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2023] [Revised: 11/09/2023] [Accepted: 01/22/2024] [Indexed: 02/17/2024]
Abstract
BACKGROUND Long COVID encompasses a heterogeneous set of ongoing symptoms that affect many individuals after recovery from infection with SARS-CoV-2. The underlying biological mechanisms nonetheless remain obscure, precluding accurate diagnosis and effective intervention. Complement dysregulation is a hallmark of acute COVID-19 but has not been investigated as a potential determinant of long COVID. METHODS We quantified a series of complement proteins, including markers of activation and regulation, in plasma samples from healthy convalescent individuals with a confirmed history of infection with SARS-CoV-2 and age/ethnicity/sex/infection/vaccine-matched patients with long COVID. FINDINGS Markers of classical (C1s-C1INH complex), alternative (Ba, iC3b), and terminal pathway (C5a, TCC) activation were significantly elevated in patients with long COVID. These markers in combination had a receiver operating characteristic predictive power of 0.794. Other complement proteins and regulators were also quantitatively different between healthy convalescent individuals and patients with long COVID. Generalized linear modeling further revealed that a clinically tractable combination of just four of these markers, namely the activation fragments iC3b, TCC, Ba, and C5a, had a predictive power of 0.785. CONCLUSIONS These findings suggest that complement biomarkers could facilitate the diagnosis of long COVID and further suggest that currently available inhibitors of complement activation could be used to treat long COVID. FUNDING This work was funded by the National Institute for Health Research (COV-LT2-0041), the PolyBio Research Foundation, and the UK Dementia Research Institute.
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Affiliation(s)
- Kirsten Baillie
- Division of Infection and Immunity, Cardiff University School of Medicine, University Hospital of Wales, Heath Park, Cardiff CF14 4XN, UK
| | - Helen E Davies
- Department of Respiratory Medicine, University Hospital of Wales, Llandough, Penarth CF64 2XX, UK
| | - Samuel B K Keat
- Division of Infection and Immunity, Cardiff University School of Medicine, University Hospital of Wales, Heath Park, Cardiff CF14 4XN, UK
| | - Kristin Ladell
- Division of Infection and Immunity, Cardiff University School of Medicine, University Hospital of Wales, Heath Park, Cardiff CF14 4XN, UK
| | - Kelly L Miners
- Division of Infection and Immunity, Cardiff University School of Medicine, University Hospital of Wales, Heath Park, Cardiff CF14 4XN, UK
| | - Samantha A Jones
- Department of Respiratory Medicine, University Hospital of Wales, Llandough, Penarth CF64 2XX, UK
| | - Ermioni Mellou
- Division of Infection and Immunity, Cardiff University School of Medicine, University Hospital of Wales, Heath Park, Cardiff CF14 4XN, UK
| | - Erik J M Toonen
- R&D Department, Hycult Biotechnology, Frontstraat 2A, 5405 PB Uden, the Netherlands
| | - David A Price
- Division of Infection and Immunity, Cardiff University School of Medicine, University Hospital of Wales, Heath Park, Cardiff CF14 4XN, UK; Systems Immunity Research Institute, Cardiff University School of Medicine, University Hospital of Wales, Heath Park, Cardiff CF14 4XN, UK
| | - B Paul Morgan
- Division of Infection and Immunity, Cardiff University School of Medicine, University Hospital of Wales, Heath Park, Cardiff CF14 4XN, UK; Systems Immunity Research Institute, Cardiff University School of Medicine, University Hospital of Wales, Heath Park, Cardiff CF14 4XN, UK.
| | - Wioleta M Zelek
- Division of Infection and Immunity, Cardiff University School of Medicine, University Hospital of Wales, Heath Park, Cardiff CF14 4XN, UK; Systems Immunity Research Institute, Cardiff University School of Medicine, University Hospital of Wales, Heath Park, Cardiff CF14 4XN, UK
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