CMV

The cytomegalovirus (CMV) is a widespread pathogen responsible for generally asymptomatic and persistent infections in healthy people. The virion of CMV consists of a 100-nm diameter icosahedral nucleocapsid containing a 230-kbp, double-stranded linear DNA genome surrounded by a proteinaceous layer defined as the tegument or matrix, which, in turn, is enclosed by a lipid bilayer containing a large number of viral glycoproteins. The mature virion particle is 150–200 nm in diameter. HCMV-infected cell cultures produce the infectious virions and another two types of morphological particles: noninfectious enveloped particles and dense bodies (DB). Noninfectious enveloped particles are defective viral particles composed of enveloped immature capsids (type B) that lack DNA but contain the viral scaffolding/assembly protein (AP) normally absent from fully mature nucleocapsids (C-capsids).

The HCMV genome is the largest of all herpesviruses and has a high G+ C content. Like that of herpes simplex virus-1, it contains an arrangement of unique long (UL), unique short (US), and repeat regions. Since each long and short region can be oriented in either direction, four genome isomers are produced in viral progeny (Class E structure).