Adenovirus

Introduction

• Non-enveloped linear ds-DNA virus. Icosahedral symmetry (70-90 nm diameter).
• The capsid has three major proteins – hexon, penton, and fibre.
• Ubiquitous in nature. Most people are seropositive by the age of 10 years.
• Adenovirus can be divided into 4 genera.
  Mammalian adenovirus belongs to the genus Mastadenovirus.
  Human adenovirus is a part of this genus.

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Human adenovirus has 7 species based on their haemagglutination character.
Each species was divided into serotypes based on neutralisation (e.g. A- 12,18, 31). At present, genotyping is being used to classify Adenovirus.
Different species of human adenovirus have different tissue tropism.

Species	Tissue tropism
A	GI, respiratory, urinary
B	GI, Eye, respiratory, urinary
C	GI, respiratory, urinary
D	GI, Eye
E	Eye, respiratory
F	GI
G	GI

Adenovirus receptors

• Coxsackie B virus–adenovirus receptor (CAR),
• CD46, CD80, CD86
• Sialic acid, heparan sulfate proteoglycans.

Viral replication

Viral replication occurs in the nucleus.

DURING THE REPLICATION PROCESS VIRUS RELEASES PROTEINS TO MODULATE THE IMMUNE SYSTEM

• Inhibit MHC-1 expression
• Downregulation of fas, TNF
• Inhibition of apoptosis (TRAIL receptor)

Latent infection

Adenovirus can remain latent in the T-lymphocytes of the tonsil and adenoid.

Route on transmission

Droplet, faeco-oral.

Adenovirus infection

Adenovirus is commonly seen in 3 groups of people – children, immunocompromised and military recruits.
50% of adenovirus infection is asymptomatic.
Up to 10% of febrile illnesses in children are due to adenovirus.

Laboratory diagnosis:

Method	Notes
Culture	Not readily available outside reference lab/research facility. Serotype 40,41 – cannot be cultured. The patient may shed the virus for days to a couple of weeks, but an immunocompromised patient may shed the virus much longer.
Serology	Immunofluorescence assay – low sensitivity (40-60%), lower sensitivity in an immunocompromised patient. ELISA – a fourfold rise in titre is used to diagnose infection.
PCR	Commonly used method. Quantitative PCR can be used to measure treatment response.
Typing	Haemagglutination, Neutralisation, Whole-genome sequencing, Phylogenetic analysis.
Histopathology	Typical finding, smudge cell.

Treatment:

Immune reconstitution	Reduction in immunosuppression.
Cidofovir	In vitro activity against adenovirus. Limited clinical data. Toxicity – nephrotoxic, GI toxicity. The oral liposomal formulation is being trialled.
Ribavirin	Limited clinical data. Active against group C adenovirus.
Vidarabine	Limited clinical data.
Ganciclovir	Limited clinical data
Immunotherapy	Adoptive T-cell therapy. Investigational therapy.

Vaccine:

A vaccine has been developed for military recruits.