Epstein--Barr virus binding to CD21, the virus receptor, activates resting B cells via an intracellular pathway that is linked to B cell infection

Department of Immunology, IMM-19, The Scripps Research Institute, 10666 North Torrey Pines Road, La Jolla, CA 92037, USA Epstein—Barr virus (EBV) initiates infection of normal B lymphocytes by binding to CD21, a complement receptor. Since EBV, unlike most viruses, preferentially infects resting (non-activated) cells, the present studies were undertaken to evaluate the hypothesis that intracellular signalling pathway(s) triggered by EBV binding to CD21 activate the expression of certain cellular genes, as well as the initially expressed viral genes, and thus enable EBV to infect resting B cells. Experiments with non-transforming EBV, recombinant virus ligand and anti-CD21 MAbs show that EBV binding to CD21 on resting B cells increases CD23 mRNA levels independently of viral gene expression. A panel of five protein kinase C (PKC) and tyrosine kinase (PTK) inhibitors, all with different modes of action, exhibited a distinctive pattern of effects on the EBV induced induction of CD23 expression, ranging from nearly complete inhibition to no influence. The results suggest that distinct PKC isoforms and PTKs are involved in the signalling pathway(s) triggered by EBV binding to CD21. Significantly, the five inhibitors showed the same pattern of effects on the earliest stages of infection (EBNA-2 transcription) and B cell transformation (mitogenesis and colony formation). The identical pattern of effects of these PKC and PTK inhibitors with diverse mechanisms of action on the EBV induced increase in both CD23 and EBNA-2 mRNA levels strongly suggests that their transcription is mediated by an intracellular signalling pathway which shares, at least in part, common members. Present address: Isis Pharmaceutical, Carlsbad, Calif., USA. Present address: R. W. Johnson Pharmaceutical Research Institute, La Jolla, Calif., USA. Received 25 March 1996; accepted 6 August 1996.