Comparative virion structures of human herpesviruses

Excerpt

The herpesvirus family consists of a group of viruses distinguished by the large size of their linear double-stranded DNA genomes (∼130–250 kbp) and a common architecture of infectious particles (Fig. 3.1) (Chiu and Rixon, ; Gibson, ; Steven and Spear, 1997). Indeed, before the birth of molecular biology and the availability of genomic sequencing, the common hallmark structural features shared by these viruses were the most important criteria for the classification of a herpesvirus (Roizman and Pellett, 2001). All herpesviruses identified to date, which include eight different types that are known to infect human, and more than 170 other viruses that are found in animals as well as in fish and amphibians (Roizman and Pellett, 2001), exhibit identical structural design as illustrated using human cytomegalovirus shown in Fig. 3.1. These viruses have a highly ordered icosahedral-shape nucleocapsid of about 125–130 nm in diameter, which encases the viral DNA genome. The nucleocapsid is surrounded by a partially ordered proteinaceous layer called the tegument, which in turn is enclosed within the envelope, a polymorphic lipid bilayer containing multiple copies of more than 10 different kinds of viral glycoproteins that are responsible for viral attachment and entry to host cells.