The adenovirus is highly contagious and often infects the upper respiratory tract in humans. The virus can cause many different conditions such as conjunctivitis, ear infections, croup, tonsilitis, and gastroenteritis.
The adenovirus is quite complex in its various classifications. Adenovirus classification falls into 57 different types that are observed in humans in seven species (A-G) of the virus. In addition, Adenoviridae can be placed into five genera when not focusing on the human interactions of the virus. These genera are Aviadenovirus, Mastadenovirus, Siadenovirus, Ichtadenovirus, and Atadenovirus. These adenovirus classifications are described below:
- Genus Atadenovirus. These infect animals of the vertebrate class such as mammals and birds.
- Genus Aviadenovirus. These infect birds and have varying effects depending on type of bird infected.
- Genus Ichtadenovirus. These infect certain types of fish species.
- Genus Mastadenovirus. These infect humans.
- Genus Siadenovirus. These infect frog species.
Structure Of The Adenovirus
Adenoviridae are medium-sized (90-100 nm) viruses, but are among the largest non-enveloped viruses which enables them to be easily transported through the endosome. The nonenveloped nature of the virus also exhibits a unique fiber which is associated with each penton base of the capsid. Attachment to the host cell is accomplished via the coxsackie-adenovirus receptor found on the surface of the host cell.
Genome And Replication Of The Adenovirus
The virus can carry 20 to 44 genes mainly because of its size. The virus is linear, non-segmented double stranded DNA. Although it is still by all means
a very simple virus, it does rely heavily on the host cell for its survival and replication behavior.
Replication takes place in the nucleus of mammalian cells by means of the host’s replication function. The life cycle is broken down into two phases: an early
and late phase. The early genes express regulatory proteins which act to switch on other virus genes, to avoid premature death, and to synthesize DNA. The late
phase of the adenovirus life cycle focuses mainly on DNA replication and lysis of the cell.
Outline Of The Adenovirus Types
- A: 12, 18, 31
- B: 3, 7, 11, 14, 16, 21, 34, 35, 50, 55
- C: 1, 2, 5, 6, 57
- D: 8, 9, 10, 13, 15, 17, 19, 20, 22, 23, 24, 25, 26, 27, 28, 29, 30, 32, 33, 36, 37, 38, 39, 42, 43, 44, 45, 46, 47, 48, 49, 51, 53, 54, 56
- E: 4
- F: 40, 41
- G: 52
image credit: “Adenovirus 3D schematic” by Thomas Splettstoesser (www.scistyle.com)