Introduction

Abstract

The herpesviruses all contain large, linear, double-stranded DNA genomes that vary between 150–230 kilobase pairs in length. In the virus particle, this DNA is contained within a toroidal core, made of proteins about 75 nm in diameter. The DNA-protein core is packaged in an icosahedral capsid composed of 162 capsomers, which in turn surrounds a protein tegument that appears as a granular zone of globular protein in electron micrographs. The icosahedron is wrapped in a lipid envelope containing several virus encoded glycoproteins that appear as short projections from the envelope in photomicrographs (Roizman and Lopez 1985). The neurotropic herpesviruses, herpes simplex types 1 and 2 and varicella zoster virus (sometimes called the alpha group of herpesviruses), and the lympho-tropic cytomegalovirus (a beta-group herpesvirus) have not convincingly been shown by epidemiological studies to be involved in oncogenic processes. Nor has it been possible to demonstrate convincingly that any of these viruses encodes a gene or induces an activity which results in the transformation of cells in culture. On the other hand, the gamma-group herpesviruses, including Epstein-Barr virus (EBV), herpesvirus saimiri, herpesvirus ateles, and Marek’s disease virus, have all been shown to be causally associated with B- and T-cell lymphomas and, in the case of EBV, nasopharyngeal carcinoma (Roizman and Lopez 1985). Part V contains a set of articles reviewing the gamma herpesviruses genes and gene products involved in viral episome replication and transformation of cells in culture.