Based on their genomic organisation, tissue tropism, and other biological characteristics, herpesviruses are classified into three categories: α, β, and γ. Of these, the γ-herpesviruses are able to replicate and persist in lymphoid cells and some are capable of infecting other cell types, such as epithelial cells and fibroblasts. The γ-herpesviruses comprise two important genera: the lymphocryptoviruses (also referred to as γ-1 herpesviruses) and the rhadinoviruses (γ-2 herpesviruses).

This themed issue principally concerns the biology and pathological effects of one of the human γ-herpesviruses—the Epstein-Barr virus (EBV)—which is a γ-1 herpesvirus carried by over 90% of the world's adult population as a lifelong asymptomatic infection. EBV is of particular interest to cell biologists, virologists, and pathologists alike because it is epidemiologically, serologically, and directly (by virtue of the detection of the virus genome and gene products in tumour cells) linked to a variety of human cancers. EBV associated cancers include several lymphoid disorders (Burkitt's lymphoma, Hodgkin's disease, post transplantation/human immunodeficiency virus associated lymphoproliferative disease, and some T cell lymphomas) and epithelial tumours (nasopharyngeal carcinoma and gastric carcinoma). All of these tumours are characterised by the presence of multiple extrachromosomal copies of the circular viral genome (episome) in every tumour cell and the expression of EBV encoded latent genes, which contribute to the malignant phenotype. The challenge is to understand the role of this virus in the development of its associated malignancies in the hope that this will provide alternative means to prevent or treat these tumours.

In the opening article in this issue, John Nicholas¹ overviews the organisation of γ-herpesvirus genomes and discusses mechanisms of genomic variation between different virus groups. The γ-herpesvirus genomes are organised into blocks of genes that are conserved across all γ-herpesviruses. These so called “core” genes include those that function as “housekeeping” genes, often …