Adenoviruses were first isolated in 1953 by Rowe and
co-workers from human adenoids removed at surgery.
There are 51 immunologically
distinct
human adenovirus serotypes -
(6
species: Human
adenovirus A through F).
Many serotypes are not linked to a specific disease.
Human adenoviruses have a capsid with icosahedral
symmetry.
Rodlike structures with knobs at the ends protrude from
the capsid.
Image Link
[This
image shows gold clusters (bright yellow) bound to the knob protein on
adenovirus.]
The genome of the virus is a double-stranded DNA linear
molecule.
When infecting cells in
vitro, adenoviruses are capable of lytic infection, latent infection,
and transformation.
Because of the ability to transform cells and to
produce tumours in rodents, they have been considered possible human
tumour viruses, but up to now there has been no evidence that links
adenoviruses to human tumours.
Adenoviruses are associated with the following
diseases : coryza and pharyngitis in infants ; upper respiratory
disease, pharyngoconjunctival fever, and hemorrhagic cystitis in
children, acute respiratory disease and pneumonia in young adults ; and
epidermic keratoconjunctivitis and pneumonia in immunocompromised and
normal adults.
Adenoviruses that are difficult to culture have been
associated wih 7% to 17% of cases of diarrhea in children.
Adenovirus pneumonia is characterized by necrotizing
bronchitis and bronchiolitis.
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.
There is intense necrosis and desquamation of the
respiratory epithelium into the bronchial lumens.
These foci of bronchiolitis are surrounded by areas of
consolidation, hemorrhage, and atelectasis.
At low power the appearance may be confused with the bacterial
bronchopneumonia
.
In the areas of consolidation and among the
necrotizing bronchiolar epithelial lesions, cells with intranuclear
inclusion bodies may be found.
In the early stages cytopathic effects are manifested
by granular, slightly enlarged nuclei containing eosinophilic bodies
intermixed with clumped basophilic chromatin.
The eosinophilic bodies coalesce, forming larges masses
to end as a central, granular, ill-defined mass surrounded by a halo.
The second type of inclusion, which is more common and
probably corresponds to a late-stage infected cell, is designated the
“smudge cell”.
The nucleus is rounded or ovoid, large, and completely
occupied by a granular amphophilic to deeply basophilic mass.
There is no halo, and the nuclear membrane and nucleus
are indistinct.
Electron microscopy of the lung demonstrates viral
particles in the bronchiolar and alveolar lining cells.
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