IL27RA ubiquitination by CBL E3 ligase regulates IL27 dependent immune response against EBV- induced infectious mononucleosis

Epstein-Barr virus (EBV) is a trigger of robust immune responses and infectious mononucleosis (IM). Although EBV induces interleukin-27 (IL-27) in B cells, and IL-27 receptor alpha (IL27RA) deficiency increases EBV susceptibility, the regulatory mechanisms linking E3 ubiquitin ligases such as Casitas B-lineage lymphoma (CBL) to IL27RA during EBV infection remain unknown. IL27RA-interacting proteins were identified by immunoprecipitation-mass spectrometry (IP-MS), co-immunoprecipitation (Co-IP), and GST pull-down. Ubiquitination and degradation of IL27RA were assessed in human PBMCs with or without CBL overexpression. Functional assays included EBV-reactive T cell responses, flow cytometry, immunoblotting and cytokine stimulation. RNA-seq-based transcriptomic analysis was performed on IL27RA-deficient cells. CBL directly bound IL27RA, promoting its ubiquitination and proteasomal degradation. CBL depletion stabilized IL27RA, whereas CBL overexpression reduced IL27RA levels, suppressing STAT1/STAT3 phosphorylation and IL-27 signaling. CBL-overexpressing PBMCs showed heightened EBV-induced cell death. RNA-seq identified IL27RA-dependent dysregulation of pathways related to immune communication, hypoxia, and antiviral defense. CBL negatively regulates IL-27 signaling by degrading IL27RA, impairing antiviral immunity and exacerbating EBV immunopathogenesis. Therapeutic targeting of the CBL–IL27RA axis may benefit EBV-associated diseases.