Systemic and mucosal antibody secretion specific to SARS-CoV-2 during mild versus severe COVID-19
cell biology clinical diagnostics immunology/immunity
Authors: Cervia and Nilsson et al
Link to paper: https://www.biorxiv.org/content/10.1101/2020.05.21.108308v1
Journal/ Pre-Print: bioRxiv
Tags: Cell Biology, Clinical, Diagnostics, Immunology/Immunity
Research Highlights
1. Characterisation of SARS-CoV-2 antibody response in relation to disease severity
2. Analysis of mucosal antibody titers in exposed healthcare workers revealed detectable SARS-CoV-2 IgA in nasal fluids in some cases where serum IgA/IgG levels remained undetectable
3. Identification of serum IgA levels as potential prognostic biomarker for disease severity
Summary
Cervia, Nilsson et al aimed to characterise the determinants of SARS-CoV-2-specific antibody responses in two different cohorts, patients with mild versus severe COVID-19 and SARS-CoV-2 exposed healthcare workers. Serum IgG levels were negative or increased slightly late after symptom onset in mild COVID-19 patients, whereas serum IgG and IgA increased significantly in severe COVID-19 patients. High serum IgA levels correlated with severe acute respiratory distress syndrome (ARDS). Analysis of nasal fluids and tears of healthcare workers alongside serum levels suggested that high nasal IgA correlated with a more mild course, whereas high serum IgA correlated with a more severe disease course, however serum and mucosal antibody levels were not directly compared.
Impact for SARS-CoV2/COVID19 research efforts
Understand the immune response to SARS-CoV2/COVID19: analysis of IgA/IgG humoral response in relation to severity of disease, measurement of antibodies in mucosal fluids
Clinical symptoms and pathogenesis of SARS-Cov2/COVID19: correlation of disease severity and symptoms with disease progression, exposure, sex, and age
Develop diagnostic tools for SARS-CoV2/COVID19: proposal of serum IgA as prognostic biomarker of disease severity
Study Type
· Clinical Cohort study
Strengths and limitations of the paper
Novelty: Correlation of antibody response with COVID-19 severity, IgA serum levels as biomarkers, mucosal SARS-CoV-2 specific antibodies in exposed healthcare workers
Standing in the field: SARS-CoV-2 specific IgA as prognostic marker for disease severity has been proposed in an earlier longitudinal study
Appropriate statistics: Statistics seem well thought-through
Viral model used: Immunoassays using SARS-CoV-2 spike protein, cohort with patients infected with SARS-CoV-2
Translatability: Low antigen exposure will elicit mucosal IgA-mediated response, which could be protective for health care workers (also inversely correlated with age)
Main limitations: longitudinal study underpowered (n=2) and shows huge variation is IgA responses within mild cases, making conclusions difficult. Serum and mucosal antibody level correlation was not investigated but would have been important to validate their hypothesis regarding site specific IgA and disease course.
The antibody response should have been tested against additional antigens other than S1