Fig. 1. Schematic drawing of an infectious virus particle (virion) of herpes simplex virus type 1. An icosahedral protein structure termed the capsid surrounds the double-stranded DNA genome that is wound on a protein spindle (toroid). This combined structure is termed the nucleocapsid. Surrounding the nucleocapsid is a phospholipoprotein structure termed the envelope that is a cellular membrane modified by the insertion of different virus-induced glycoproteins. These glycoproteins form spikes that project from the surface of the virion. The tegument is an amorphous protein structure between the nucleocapsid and the envelope that contains important regulatory proteins. (Liesegang TJ: Biology and molecular aspects of herpes simplex and varicella-zoster virus infections. Ophthalmology 99:781, 1992)