MicroRNA-mediated regulation of the immune response in Calu-3 cells infected with a SARS-CoV-2 E gene variant

Area of Science:

• Virology
• Molecular Biology
• Immunology

Background:

• Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) infection disrupts the alveolar epithelial barrier, exacerbating airway inflammation.
• The SARS-CoV-2 envelope (E) protein is implicated in epithelial damage and sustained inflammation.
• A specific SARS-CoV-2 variant, F8, with a deletion in the E gene, induces higher inflammatory factor expression compared to wild-type strains.

Purpose of the Study:

• To analyze microRNA (miRNA) expression profiles in Calu-3 cells infected with the F8 SARS-CoV-2 variant versus the wild-type 8X strain.
• To elucidate the regulatory roles of differentially expressed miRNAs in host signaling pathways, particularly inflammatory responses and barrier function.

Main Methods:

• Differential miRNA expression profiling in infected Calu-3 cells.
• Quantitative Reverse Transcription Polymerase Chain Reaction (RT-qPCR) for miRNA validation.
• Enzyme-Linked Immunosorbent Assay (ELISA) and other functional assays to determine miRNA regulatory roles.

Main Results:

• F8 infection significantly upregulated miR-361-3p and downregulated let-7b-5p in Calu-3 cells.
• miR-361-3p targets TSPAN1, inhibiting it and promoting PTEN expression, thus regulating the PI3K-Akt pathway.
• Downregulation of let-7b-5p may increase inflammatory cytokines (IL-6, IL-8, PTX3) and disrupt ZO-1 expression, affecting barrier integrity.

Conclusions:

• The SARS-CoV-2 E protein mutant F8 remodels the host miRNA network to coordinate immune responses and maintain barrier function.
• These findings offer insights into the pathogenesis of SARS-CoV-2 variants and their impact on host cellular processes.