The Relationship between the Clinical Course of SARS-CoV-2 Infections and Expression of Bruton's Tyrosine Kinase

INTRODUCTION: Bruton's Tyrosine Kinase (BTK), an important element for the production of several inflammatory cytokines, may play a role in the pathogenesis of COVID-19. This study aimed to assess BTK gene expression levels in COVID-19 cases based on disease severity and outcome. METHODS: In this study, 33 hospitalized patients with COVID-19 were recruited and divided into two groups based on the severity of the disease: "mild to moderate" and "severe to critical". A blood sample was taken from each patient, peripheral blood mononuclear cells (PBMCs) were extracted, and BTK gene expression was measured. The level of BTK gene expression was compared based on the demographic data, laboratory results, and the severity and outcome of the disease. RESULTS: Among the 33 patients, 22 (66.7%) were male, with nearly half having at least one underlying condition. The severity groups comprised 12 patients in the "mild to moderate" category and 21 in the "severe to critical" category, with eight (24.2%) experiencing fatal outcomes. Age, weight, and BMI showed no significant associations with BTK expression. BTK expression was notably lower in "severe to critical" and ICU-admitted cases, as well as in individuals with low O2 saturation. However, no significant difference in BTK expression was observed between cured and deceased patients (p = 0.117). CONCLUSION: BTK gene expression in PBMCs exhibited an inverse correlation with COVID- 19 severity. However, no difference was found between BTK expression and disease outcome.