Gene Delivery Using Viral Vectors - Challenges in Delivery of Therapeutic Genomics and Proteomics - page 244

Herpesviridae , which infects humans. Both HSV-1 and -2 are ubiquitous and conta-
gious, and they can be spread when an infected person is producing and shedding the
virus.

5.5.1.1 Virus Classification
Group: Group I (dsDNA)
Family: Herpesviridae
Subfamily: Alphaherpesvirinae
Genus: Simplexvirus
Species: Herpes simplex virus 1 (HWJ-1), Herpes simplex virus 2 (HWJ-2)

5.5.1.2 Viral Structure
Herpes simplex virus (HSV) is an enveloped double-stranded DNA virus carrying more
than 80 identified genes encoded by the 152 kb viral genome [180] . The virus envelope
contains at least 10 glycoproteins that are useful for the attachment and penetration of
the virus. The structure of herpes viruses consists of a relatively large double-stranded,
linear DNA genome encased within an icosahedral protein cage called the capsid,
which is wrapped in a lipid bilayer called the envelope, and the envelope joined to the
capsid by means of a tegument. This complete particle is known as the virion. HSV-1
and -2 each contains at least 74 genes within their genomes, although speculation over
gene crowding allows as many as 84 unique protein coding genes by 94 putative ORFs,
and these genes encode a variety of proteins involved in forming the capsid, tegument,
and envelope of the virus, as well as control the replication and infectivity of the virus
( Fig. 5.10 ).
The genomes structure of HSV-1 and -2 contains two unique regions called the
long (U L ) and the short unique region (U S ). Out of the 74 known ORFs, U L contains
56 viral genes, whereas U S contains only 12. Transcription of HSV genes is catalyzed

Tegument

Figure 5.10 Structure of
herpes simplex virus.

Lipid envelope

150-200
nm

Viral DNA Capsid

Glycoproteins