Herpes simplex viruses, types 1 and 2

The herpesviruses are composed of a single molecule core of double-stranded DNA, an icosahedral structure with 162 capsomers, a granular zone, and a lipid envelope, which contains predominantly viral-specific glucoproteins. As a characteristic of the herpesvirus group, virus replication occurs in the cell nucleus. Six to eight hours after infection, synthesis and assembly of virus particles can be observed with an electron microscope. A basophilic Feulgen-positive mass centrally displaces the nuclear chromatin. Electron microscopy reveals this viral DNA core to be surrounded by a protein coat. There is a subsequent movement of the virus particle from the nucleus to the cytoplasm. This is paralleled by morphologic changes in the intranuclear inclusion body. The central ovoid intranuclear inclusion body loses both its basophilia and its affinity for DNA stains. The lesion is characterized by an eosinophilic, irregular central intranuclear inclusion body rimmed by peripheral fragments of chromatin at the margins of the nuclear membrane (Fig. 1). The virion obtains its final envelope from the nuclear membrane.