Introduction to the human γ-herpesviruses

Introduction This chapter will provide a brief background into the ?-herpesviruses family in comparison to other members of the herpesvirus family; but the primary focus of this chapter will be to recount the discovery of the two human ?-herpesviruses (EBV and KSHV) and the diseases associated with infection of each virus, a brief introduction into their life cycles, and finally a description of the genome characteristics of the viruses including a description of their respective genomes. In many ways, the discovery and association with human diseases for both EBV and KSHV have many parallels despite almost three decades separating their discoveries and association with human disease. The γ-herpesvirus family The γ-herpesviruses are a subfamily of herpesviruses that were first distinguished by their cellular tropism for lymphocytes. Subsequent molecular phylogenetic analyses have confirmed the close relationship among these viruses that is distinct from the α- and β-herpesviruses subfamilies (Fig. 22.1). Gammaherpesvirinae is currently divided into two genera, Lymphocryptoviridae which includes human Epstein-Barr virus (EBV or HHV 4) and Rhadinoviridae, which includes human Kaposi's sarcoma-associated herpesvirus (KSHV or HHV 8). Recent studies suggest that primate rhadinoviruses can be further subdivided in KSHV -like viruses, a second closely related but distinct lineage of Old World primate viruses related to the rhesus rhadinovirus (RRV), and the New World monkey rhadinoviruses represented by herpesvirus saimiri (HVS). A more detailed analysis of the non-human ?-herpesviruses will be discussed in Chapters 60 and 61.