MOLECULAR BIOLOGY OF THE HSV
Herpes viruses are large, enveloped DNA viruses comprising a genome of double-stranded DNA 150 kb in length located within the viral capsid and encoding some 100-200 genes (see diagram one). Typically, glycoprotein C mediates viral entry by interacting with heparin sulphate, thus initiating a series of interactions ultimately resulting in entry into the cell. Once in the cytoplasm, the viral capsid is transported to nuclear membrane pores where it injects its genome through its capsid portal. Subsequent to nuclear entry, the immediate-early, early and late genes are transcribed in a sequential order resulting in viral DNA replication and a lytic infection, where new viral particles are produced and released from the cell. Conversely, a latent infection may also take place, where the virus persists in a quiescent but persistent form. During the latent infection, the virus expresses the latency-associated transcripts, which regulate the host cell genome, preventing the induction of cell death. Herpes viruses have been explored as gene transfer vectors due to their capacity to carry long sequences of exogenous DNA and their natural ability to target the nervous system.
Diagram One: The HSV Genome
