Inhibition of Cell Growth and Epstein-Barr Virus Reactivation by CD40 Stimulation in Epstein-Barr Virus-Transformed B Cells

The CD40 molecule plays important roles in B cell activation, proliferation, and immunoglobulin (Ig) class switching. In Epstein-Barr virus (EBV)-transformed lymphoblastoid cell lines (LCL), CD40 mediates growth inhibition and EBV reactivation via the CD40 signaling pathways. CD40 cross-linking with a monoclonal antibody arrests cell growth in G₁ and induces expression of p27^kip1 cyclin-dependent kinase inhibitor. CD40 cross-linking also induces EBV reactivation, as detected by the induction of EBV-specific early antigen, immediate early BZLF1 RNA, and its protein product ZEBRA. These results support hypotheses that the proliferation of EBV-infected B cells in vivo can be inhibited by interactions with the CD40 ligand on activated helper T cells, and latent EBV is reactivated via the signaling pathways controlled by CD40 interactions.