Open AccessComplement dysregulation is associated with severe COVID-19 illness
Author(s) -
Jia Yu,
Gloria Gerber,
Hang Chen,
Xuan Yuan,
Shruti Chaturvedi,
Evan M. Braunstein,
Robert A. Brodsky
Publication year - 2021
Publication title -
haematologica
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.782
H-Index - 142
eISSN - 1592-8721
pISSN - 0390-6078
DOI - 10.3324/haematol.2021.279155
Subject(s) - complement system , factor h , pathogenesis , immunology , medicine , complement factor i , complement receptor 1 , atypical hemolytic uremic syndrome , complement factor b , alternative complement pathway , antibody
Severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) may manifest as thrombosis, stroke, renal failure, myocardial infarction, and thrombocytopenia, reminiscent of other complement-mediated diseases. Multiple clinical and preclinical studies have implicated complement in the pathogenesis of COVID-19 illness. We previously found that the SARS-CoV-2 spike protein activates the alternative pathway of complement (APC) in vitro through interfering with the function of complement factor H, a key negative regulator of APC. Here, we demonstrated that serum from 58 COVID-19 patients (32 patients with minimal oxygen requirement, 7 on high flow oxygen, 17 requiring mechanical ventilation and 2 deaths) can induce complement-mediated cell death in a functional assay (the modified Ham test) and increase membrane attack complex (C5b-9) deposition on the cell surface. A positive mHam assay (>20% cellkilling) was present in 41.2% COVID-19 patients requiring intubation (n=7/17) and only 6.3% in COVID-19 patients requiring minimal oxygen support (n=2/32). C5 and factor D inhibition effectively mitigated the complement amplification induced by COVID-19 patient serum. Increased serum factor Bb level was associated with disease severity in COVID-19 patients, suggesting that APC dysregulation plays an important role. Moreover, SARS-CoV-2 spike proteins directly block complement factor H from binding to heparin, which may lead to complement dysregulation on the cell surface. Taken together, our data suggest that complement dysregulation contributes to the pathogenesis of COVID-19 and may be a marker of disease severity.