In a recent cross-sectional study posted to the medRxiv* preprint server, researchers used per protocol bronchoalveolar lavage fluid (BALF) samples after intubation to evaluate the transcriptomic profiles of the local pulmonary host responses during early-stage severe coronavirus disease 2019 (COVID-19) acute respiratory distress syndrome (CARDS), non-COVID-19 ARDS, and sepsis.

Study: A unique dexamethasone-dependent gene expression profile in the lungs of COVID-19 patients. Image Credit: Alexandros Michailidis/Shutterstock

Furthermore, they analyzed the innate and adaptive immune transcriptome profiles of non- and dexamethasone (DXM)-treated CARDS patients to see how this unique immune-targeted treatment affects pulmonary host defense, including proinflammatory mediator and interferon (IFN)-stimulated gene (ISGs) expression patterns.

Local immunopathogenesis of CARDS and the effects of systemic DXM treatment on COVID-19 pulmonary immunity are still not well known.

About the study

In this study, the inclusion criteria for CARDS patients involved age greater than 18 years, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection verified by reverse transcription polymerase chain reaction (RT-PCR), ARDS according to Berlin criteria, and less than 72 hours of invasive mechanical ventilation.

All patients were enrolled between April 6, 2020, to April 12, 2021. The first and second COVID-19 waves in Denmark occurred during this time, which corresponded to the time before and after DXM treatment became standard of care. Therefore, DXM therapy was not given to patients who were recruited in the first wave. During this time, the supportive ICU therapy did not change.

Patients with ARDS caused by bacterial respiratory infections as well as mechanically ventilated patients with sepsis who did not have ARDS were included as a comparison group; both of these patient groups were referred to as non-COVID-19. The inclusion criteria were identical except for SARS-CoV-2 infection. In severely sedated patients, the BAL technique was performed per protocol in the supine position. The sample was prepared and RNA extraction as well as RNA library preparation and sequencing were carried out. In addition, an enzyme-linked immunosorbent test was used to assess IFN autoantibodies in BALF.

Results and conclusion

The researchers discovered differentially expressed genes in CARDS patients' BALF, as well as a unique RNA expression profile in DXM-treated CARDS patients compared to non-treated CARDS patients. DXM-CARDS indicated enhanced pathways for B-cell activation, antigen presentation, and complement responses, as well as the elevation of cellular metabolism and rearrangement processes. In non-treated CARDS patients, ISGs were similarly significantly elevated. Key pro-inflammatory genes for CARDS and non-COVID-19 were equivalent and did not differ irrespective of DXM therapy. Also, IFN autoantibodies were discovered in CARDS patients' lungs.

On comparing the pulmonary transcriptional profiles of CARDS and non-COVID-19 patients, the researchers were able to uncover unique local pathways of COVID-19 caused lung injury. In DXM-CARDS and non-DXM-CARDS patients, they found a total of 1,613 and 317 other differentially expressed (DE) genes, respectively, of which only 53 were elevated in both groups as compared to non-COVID-19 patients.

Although glucocorticoid treatment is known to suppress the production of at least some inflammatory cytokines in other diseases and has been proposed to improve CARDS outcomes by suppressing the "cytokine storm," they found no differences in gene expression of pro-inflammatory mediators in the lungs in response to DXM treatment.

The complement reactions, notably genes associated with the traditional pathway initiated by antigen-antibody complexes, were increased in DXM-CARDS, according to gene ontology (GO) analysis. The researchers also discovered enhanced B-cell signatures in GO and blood transcriptome module (BTM) analyses. The upregulation of the phagocytic pathway, particularly FC-gamma receptor signaling, was also discovered, which is linked to antibody-bound viruses and phagocytosis. Furthermore, the CORO1A-DEF6 network, which is associated with T-cell and phagocytic function, was found to be enriched in the BTM analysis, which has also been reported for influenza vaccination.

Glucocorticoids have been demonstrated to reduce type-I IFN-mediated responses by blocking intracellular signaling pathways and the consequent production of ISGs in previous in vitro studies of different viral infections. This was consistent with the present study observations of ISG enrichment in the BALF of non-DXM-treated CARDS patients. Furthermore, the researchers discovered one discrete cluster of ISGs that were elevated in DXM-treated patients and one cluster of ISGs that were downregulated in all CARDS patients.

In the lungs of CARDS patients, the researchers found a much greater level of antibodies against IFN- α and IFN- ω, which may have a deleterious influence on local antiviral immunity against SARS-CoV-2. To characterize the relevance of these autoantibodies on COVID-19 lung pathophysiology, future research with larger sample numbers should link BALF IFN autoantibody levels with SARS-CoV-2 virus load and ISG responses.

In conclusion, these findings add to the understanding of CARDS' pulmonary host response and the possible implications of DXM treatment, but they also raise some critical considerations, particularly regarding the concept of a local "cytokine storm" as a trigger of respiratory failure during COVID-19.

DXM treatment was not associated with regulation of pro-inflammatory pathways in CARDS but with the regulation of other specific local innate and adaptive immune responses.”

*Important notice

medRxiv publishes preliminary scientific reports that are not peer-reviewed and, therefore, should not be regarded as conclusive, guide clinical practice/health-related behavior, or treated as established information.

Written by

Saurabh Chaturvedi

Saurabh Chaturvedi is a freelance writer from Jaipur, India. He is a gold medalist in Masters in Pharmaceutical Chemistry and has extensive experience in medical writing. He is passionate about reading and enjoys watching sci-fi movies.