Epstein-Barr Virus (EBV) gene expression during infectious mononucleosis

Background: Acute infectious mononucleosis (IM) is a selflimiting lymphopro liferative disease of EBV-infected (immortalised) B cells and poly-/oligocl onal cytotoxic T cells which are to a high percentage EBV-specific. In B ce lls EBV infection mainly leads to a latent infection with expression of EBV nuclear antigens 1-6 (EBNA1-6) and membrane antigens 1,2A and 2B (LMP1,LMP 2A and LMP2B). Expression of these EBV latent antigens leads to transformat ion and immortalisation of infected B cells. Here we examined if also lytic EBV genes (i.e. BZLF1), which are associated with a productive EBV infecti on, are expressed during IM. Methods: RNA expression of EBV latent genes EBNA1,LMP1 and LMP2A and EBV ly ric gene BZLF1 in peripheral blood mononuclear cells (PBMC) of 12 patients with IM and 1 patient with acute T cell leukemia (HTLVI positive) was studi ed by nested RT-PCR and subsequent hybridisation with an EBV specific oligo nucleotide. Results: Expression of latent EBV genes, EBNA1,LMP1 and LMP2A, was found in 50%, 83% and 92%, respectively, of 12 patients with IM. Expression of lyti c EBV gene BZLF1 was detected in 58%. One patient with T cell leukemia exhi bited expression of ail latent EBV genes and of lytic EBV gene BZLF1. Conclusion: EBV lytic gene BZLF1 is expressed during IM in a high percentag e. Certain nucleosidanaloga (i.e, aciclovir and others), which inhibit only lytic but not latent EBV infection, may eventually be useful in complicate d and chronic EBV infections, when EBV lytic infection is present.