The molecular biology of Epstein-Barr virus

Epstein-Barr virus (EBV) was discovered in continuously growing tumor cells derived from African patients with Burkitt's lymphoma. In the intervening twenty years, much biological and biochemical information has been accumulated. The virus infects B lymphocytes and occupies a unique position among human herpesviruses in that it is the only one which is capable of forming a latent infection whereby complete copies of the virus genome persist in growth transformed cells. Since there are no fully permissive cell systems of virus replications, only the established B cell lines are available for study of the molecular events of EB virus in infected cells. A viral cycle consists of four stages, latent, early replicative, middle replicative and late replicative stages. In the latent state, only small parts of the viral genome are transcribed and express transformation proteins: nuclear antigens (EBNAs) and lymphocyte determined membrane antigen (LYDMA). After reactivation of viral genome and during a productive cycle, more than 50 RNAs are expressed and over 30 viral-specified polypeptides are detectable by immunoprecipitation with a high titer human anti-EBV serum. During the early replicative stage, early antigens (EA) and DNA enzymes, both necessary for DNA synthesis, are synthesized. In the late replicative stage, about 30-40 mRNA are transcribed and two major late antigen complexes, viral capsid antigens (VCA) and membrane antigens (MA), are identified. These antigens are indispensable for the formation of virions.