12 Herpes Simplex Viruses

Abstract

Herpesviruses have been isolated from humans and many different animal species, and they vary considerably with respect to host range and biological properties. There are at least five distinct human herpesviruses, namely, herpes simplex viruses types 1 and 2 (HSV-1 and HSV-2), varicella zoster virus, cytomegalovirus, and Epstein-Barr virus (EBV). The differential characteristics of the herpesvirus family are a linear, double-stranded DNA genome, ranging in molecular weight from approximately 80 × 10⁶ to 150 × 10⁶; an icosahedral nucleocapsid exhibiting 162 capsomers on the surface; and a membranous envelope, which is acquired as the nucleocapsid buds through virus-modified patches of cellular membrane.

Although the clinical syndromes associated with HSV infections have been known for centuries and the virus was isolated and grown in a heterologous host over 50 years ago, both the viruses and the virologists interested in them languished in relative obscurity for many years. The recent awakening of interest can be attributed to five factors: (1) HSV has become a major cause of venereal infections that have reached a quasi-epidemic stage with few real prospects for control and treatment, although these are widely discussed. (2) The full range of severe clinical syndromes resulting from infection by these viruses has only recently been fully appreciated; they are indeed life-threatening to the newborn and to the immunologically compromised host (Nahmias and Roizman 1973; Rawls 1973). (3) A number of herpesviruses that infect humans and animals have been associated with cancer, and HSV has become suspect as a possible cause of...