Adenovirus is an interesting, and in some ways, frightening virus. The name adenovirus comes from the initial isolation of the virus from human adenoids and was first discovered by Wallace Rowe in 1953. Dr. Rowe along with his colleague Robert Huebner were trying to isolate and identify the virus responsible for the common cold. To this end, the team were working with explants of adenoids and tonsils in cell culture. This is when Dr. Rowe observed that some cultures of the cells had a latent virus within. This led to the discovery of a viral infection in the adenoid and tonsil cells and hence the adenovirus was first discovered.
There are many known types of adenovirus and in laboratory testing there have been known occurrences of certain types of adenovirus to cause tumors in animals.
Adenovirus is a medium sized non-enveloped virus. It has no outer lipid bi-layer, and contains a double stranded DNA genome. Strands of adenovirus are capable of infecting a wide variety of vertebrae hosts, including humans, and a very broad array of animals. Infection can cause a wide array of complications from respiratory disease to conjunctivitis to gastroenteritis. Human adenovirus is under the classification of Genus Mastadenovirus and includes over 50 identified types. These are divided into seven different species types and each of these species is given a letter from A to G.
Because of its size the adenovirus is able to be transported through the endosome. It is capable of carrying from 22 to 40 genes. It is a very simple virus, and is ultimately considered dependent on its host cell for survival and replication, and is composed of around 1 million amino acid residues. Adenovirus uses the host cell’s replication capability, and enters the nucleus of the host cell. Some types of adenovirus can even transform host cells in certain types of conditions. This is thought to be how tumors are formed in some laboratory experiments on animals.
There are a number of different types of symptoms that may be exhibited from adenovirus infection in humans. These symptoms can vary from mild respiratory symptoms, to serious neurological problems. The most mild can be in many ways just like the common cold. Diarrhea and nausea, and even diarrhea mixed with blood can begastrointestinal symptoms resulting from an adenovirus infection. Eye problems like redness, tearing, eye pain, and dryness, can also be caused from an adenovirus infection. More serious respiratory symptoms can include bronchitis and pneumonia. In rare cases some neurological effects of the virus can be observed in patients, such as seizures.
Who Can Become Infected?
Adenovirus in humans is seen globally each year. In the United States alone, it is considered the most common cause of respiratory illness. Many times cases of adenovirus infection are not properly attributed to the virus because symptoms can be mild, so it can often be confused as influenza. It should be noted that anyone can become infected with adenovirus. Most infections are not serious except in those with a weakened immune system or when the virus is seen in infants. The virus is easily transmitted to the individual if he or she comes into contact with a surface that contains the virus and then rubs the eyes, nose, or mouth.
Perhaps the most interesting thing about the virus is that although it is a common cause of sickness in humans it is also used in scientific research to develop vaccines for other infections. In gene therapy, adenovirus is used as a vector to carry the new gene into the cells. When it is successful, it can help to create new and correctly functioning genes. Gene therapy is an exciting and rapidly developing field of treatment for some very serious diseases.
image courtesy of Yale Rosen from USA (Adenovirus infection) [CC BY-SA 2.0 (http://creativecommons.org/licenses/by-sa/2.0)], via Wikimedia Commons