Viruses Genomes - HUMAN ADENOVIRUS

Human adenovirus is a double stranded, non-enveloped, DNA virus of the family Adenoviridae. There are at least 51 antigenically unique serotypes or species categorised into six subgenera (A-F). They have icosahedral capsids with twelve vertices and seven surface proteins. The virion is non-enveloped, spherical and about seventy to ninety nm in size and the genome encodes about thirty proteins. Both strands of adenovirus DNA encode genes. There are a number of virus groups which have double-stranded DNA genomes of considerable size and complexity. In many respects, these viruses are genetically very similar to the host cells which they infect, Human adenovirus is one of these.

Human adenovirus was first isolated in 1953 and was soon recognised as an invaluable tool for investigating mammalian molecular biology. Several of the distinguishing features of adenovirus have made it the preferred vehicle for gene transfer and transgene expression in mammalian cells.

Adenoviruses are a frequent cause of acute upper respiratory tract (URT) infections, they also cause a number of other types of infection most of which are mild. The pathology is primarily from inflammation and loss of infected epithelial cells. Adenovirus usually causes a localised infection, but generalised infection can occur in immunocompromised patients, some adenovirus subtypes cause cellular cytopathic effect (rounded, swollen cells and basophilic intranuclear inclusions). Adenovirus is responsible for five percent of acute respiratory childhood illness and ten percent of infantile gastroenteritis. Meningoencephalitis is a complication of respiratory adenovirus infection. Deaths may occur from adenovirus especially from infection by human adenovirus type 7. Transmissions occurs via ingestion by the fecal-oral route, respiration (through respiratory droplets), contact/hand-to-eye transfer or venereal transmission.

Antivirals have generally been ineffective against adenovirus infection, the vaccine against adenovirus is live, oral and attenuated in the intestine. Vaccines are administered to the military but not available for general use because of concern about the live vaccine's oncogenic potential and the level of attenuation achieved in children. Adenovirus infection results in long-lasting immunity against the specific serotype and maternal antibody is protective.

Adenoviruses have immense potential as vectors for vaccination and for gene therapy because adenoviruses can be genetically altered in vitro to code for specific proteins and not produce infectious, pathogenic viral offspring.

References:

http://www.public-health.uiowa.edu/ceid/Human_adenovirus.htm
http://www.adenovirus.com/about/
http://www.stanford.edu/group/virus/adeno/adeno.html
http://www.tulane.edu/~dmsander/WWW/335/Adenoviruses.html
http://darwin.bio.uci.edu/~faculty/villarreal/new1/vector-development.html