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Adenovirus
Introduction
• Adenoviruses can replicate and produce disease in the
respiratory, gastrointestinal, and urinary tracts and in
the eye.
• Many adenovirus infections are subclinical, and virus
may persist in the host for months.
• About one-third of the 51 known human serotypes are
responsible for most cases of human adenovirus disease.
• A few types serve as models for cancer induction in
animals.
• Adenoviruses are especially valuable systems for
molecular and biochemical studies of eukaryotic cell
processes (gene delivery vehicle).
Properties of Adenoviruses
Important Properties of Adenoviruses
Virion: Icosahedral, 70–90 nm in diameter, 252 capsomeres; fiber projects
from each vertex
Composition: DNA (13%), protein (87%)
Genome: Double-stranded DNA, linear, 26–45 kbp, protein-bound to termini,
infectious
Proteins: Important antigens (hexon, penton base, fiber) are associated with
the major outer capsid proteins
Envelope: None
Replication: Nucleus
Outstanding characteristic: Excellent models for molecular studies of
eukaryotic cell processes
Classification
• Adenoviruses have been recovered from a wide variety of
species and grouped into four genera. All the human
adenoviruses are classified in the Mastadenovirus
genus.
• Human adenoviruses are divided into six groups (A–F)
on the basis of their genetic, physical, chemical, and
biologic properties.
Classification
Classification Schemes for Human Adenoviruses
Hemaggluthination
Oncogenic Potential
Group
Serotypes
Group
Result
Percentage of G Tumorigenicity Transformatio
+ Ca in DNA
In Vivob
n of Cells
A
12, 18, 31
IV
None
48–49
High
+
B
3, 7, 11, 14, 16,
21, 34, 35, 50
I
Monkey
(complete)
50–52
Moderate
+
C
1, 2, 5, 6
III
Rat (partial)
57–59
Low or none
+
D
8–10, 13, 15, 17,
19, 20, 22–30,
32, 33, 36–39,
42–49, 51
II
Rat
(complete)
57–61
Low or nonec
+
E
4
III
Rat (partial)
57
Low or none
+
F
40, 41
III
Rat (partial)
57–59
Low or none
+
Adenovirus Infections in Humans
Pathogenesis
• In fact, the name "adenovirus" reflects the recovery
of the initial isolate from explants of human
adenoids.
• Adenoviruses infect and replicate in epithelial cells
• Most human adenoviruses replicate in intestinal
epithelium after ingestion but usually produce
subclinical infections rather than overt symptoms.
Clinical Findings
• About one-third of the known human serotypes are commonly
associated with human illness.
• Adenoviruses 1–7 are the most common types worldwide and
account for most instances of adenovirus-associated illness.
• .
• Disease :
▫
▫
▫
▫
Respiratory Diseases
Eye Infections
Gastrointestinal Disease
Other Diseases
Respiratory Diseases
• Typical symptoms include cough, nasal congestion, fever, and sore
throat.This syndrome is most commonly manifested in infants and
children and usually involves group C viruses.
• Adenoviruses are responsible for about 5% of acute respiratory
disease in young children, but they account for much less in adults
• Adenoviruses—particularly types 3, 7, and 21, responsible for 10–
20% of pneumonias in childhood. Adenoviral pneumonia reported
for 8–10% mortality rate in the very young.
• Adenoviruses are the cause of an acute respiratory disease
syndrome among military recruits. This syndrome is characterized
by fever, sore throat, nasal congestion, cough, and malaise,
sometimes leading to pneumonia. (types 4 and 7 and occasionally by
type 3).
Eye Infections
• Mild ocular involvement may be part of the respiratory-pharyngeal
syndromes caused by adenoviruses.
• Pharyngoconjunctival fever tends to occur in outbreaks, such as at
children's summer camps ("swimming pool conjunctivitis"), and is
associated with types 3 and 7. Duration of conjunctivitis is 1–2 weeks
• A more serious disease is epidemic keratoconjunctivitis. This disease occurs
mainly in adults and is highly contagious.
Gastrointestinal Disease
• However, two serotypes (types 40 and 41) have been etiologically
associated with infantile gastroenteritis and may account for 5–15%
of cases of viral gastroenteritis in young children.
• Adenovirus types 40 and 41 are abundantly present in diarrheal
stools. The enteric adenoviruses are very difficult to cultivate.
Other Diseases
• Immunocompromised patients may suffer from a variety of casual and
severe adenovirus infections.
• The most common problem caused by adenovirus infection in transplant
patients is respiratory disease that may progress to severe pneumonia and
may be fatal (usually types 1–7).
• Children receiving liver transplants may develop adenovirus hepatitis in the
allograft. In addition, children with heart transplants who develop
myocardial adenovirus infections are at increased risk of graft loss.
• Patients with acquired immunodeficiency syndrome (AIDS) may suffer
adenovirus infections, especially in the gastrointestinal tract.
Laboratory Diagnosis
▫ Detection, Isolation, & Identification of Virus
▫ Serology
Treatment
• There is no specific treatment for adenovirus
infections.