Potential relationships between circulating gene expression of ACE2, TLR4, and IL-17 and disease severity and outcome of hospitalized patients with COVID-19.

Acute respiratory distress syndrome (ARDS) is a form of progressive hypoxemia that can be brought on by a variety of cardiorespiratory or systemic disorders, such as coronavirus disease 2019 (COVID-19). The binding of a severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) virus spike protein to the cell membrane is mediated through its binding to angiotensin-converting enzyme 2 (ACE2) receptors, resulting in viral entry, replication, and induction of a signaling cascade inducing pro-inflammatory responses that are linked to a higher mortality rate and the progression of ARDS, leading to multi-organ failure in these patients. We aimed to analyze the relationships between circulating gene expression levels of ACE2, Toll-like receptor 4 (TLR4), and interleukin-17 (IL-17) and the clinical severity of COVID-19, as well as the associated pathogenic conditions, in hospitalized patients. Sixty COVID-19 patients (34 mild/moderate COVID-19 and 26 COVID-19 with severe ARDS manifestation) and 60 healthy controls were included. The patient group was also subdivided according to outcomes into 32 recoveries and 28 deaths. ACE2, TLR4, and IL-17 levels were assessed by quantitative polymerase chain reaction (qPCR) in addition to all routine baseline laboratory investigations, including complete blood count (CBC) with differential analysis and the levels of C-reactive protein (CRP), ferritin, and d-dimer. ACE2, TLR4, and IL-17 serum expression levels were significantly higher in the COVID-19 group and subgroups and were correlated with different laboratory and clinical parameters. The serum expression levels of ACE2, TLR4, and IL-17 were accurate in differentiating between the patient groups and controls, with 86.7%, 91.7%, and 95.0% sensitivity and 96.7%, 98.3%, and 98.3% specificity, respectively, and correlated with more severe disease courses in COVID-19 patients. Higher levels are associated with overwhelmingly distressing outcomes. Our results allow us to conclude that increased circulating gene expression levels of ACE2, TLR4, and IL-17 are important in assessing the severity of COVID-19. Consequently, targeting these biomarkers may offer additional therapeutic options for COVID-19 patients in the future.