Biomedical Engineering Reference
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were first isolated in human adenoids, from which the name is derived, and are classi-
fied as group I under the Baltimore classification scheme. Some of the distinguished
features of adenovirus have made it the preferred vehicle for gene transfer and trans-
gene expression in mammalian cells. Adenoviruses are medium-sized (90-100 nm),
nonenveloped icosahedral viruses containing double-stranded DNA. There are 49
immunologically distinct types (six subgenera: A through F) that can cause human
infections. Adenoviruses are unusually stable to chemical or physical agents and
adverse pH conditions, allowing for prolonged survival outside of the body. There are
53 described serotypes in humans, which are responsible for 5-10% of upper respira-
tory infections in children, and many infections in adults as well. Thus, adenoviruses
can be potentially dangerous due to a rapid trigger of immune response
[2-4]
.
5.2.1 Classification
This family contains the following genera:
1.
Genus
Atadenovirus
; type species:
Ovine adenovirus D
2.
Genus
Aviadenovirus
; type species:
Fowl adenovirus A
3.
Genus
Ichtadenovirus
; type species:
Sturgeon adenovirus A
4.
Genus
Mastadenovirus
; type species:
Human adenovirus C
; others include AD-36
5.
Genus
Siadenovirus
; type species:
Frog adenovirus
5.2.2 Pathology
Adenoviruses are linked with a number of disorders (e.g., the common cold), most of
which are mild. The pathology is primarily from inflammation and loss of infected
epithelial cells. Viruses of subgroup C (serotype 2, 5) cause various respiratory infec-
tions in confined groups of the elderly, military recruits, and children.
5.2.3 Genome
Adenovirus is a nonenveloped 80-110 nm diameter virus presenting an icosahedral
symmetry. Human adenoviruses contain a linear, double-stranded DNA genome,
with a terminal protein (TP) attached covalently to the 5 terminal. The DNA, which
has a length of approximately 36,000 bp, is wrapped in a histone-like protein and has
inverted terminal repeats (ITRs) of 50-200 bp, which act as origins of replication.
5.2.4 Structure and Biology of Adenovirus
The structure of adenovirus contains six major parts:
1.
Hexon
2.
Linear genomic DNA
3.
Knob protein
4.
Core protein
5.
Fiber
6.
Penton base
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