What is an adenovirus?

Updated: Apr 15, 2021
  • Author: Sandra G Gompf, MD, FACP, FIDSA; Chief Editor: Michael Stuart Bronze, MD  more...
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Answer

Adenovirus, a DNA virus, was first isolated in the 1950s in adenoid tissue–derived cell cultures, hence the name. These primary cell cultures were often noted to spontaneously degenerate over time, and adenoviruses are now known to be a common cause of asymptomatic respiratory tract infection that produces in vitro cytolysis in these tissues.

A virus image from the International Committee on A virus image from the International Committee on Taxonomy of Viruses, in The Big Picture Book of Viruses, available at http://www.virology.net/Big_Virology/BVDNAadeno.html.

An extremely hardy virus, adenovirus is ubiquitous in human and animal populations, survives long periods outside a host, and is endemic throughout the year. Possessing 52 serotypes, adenovirus is recognized as the etiologic agent of various diverse syndromes. It is transmitted via direct inoculation to the conjunctiva, a fecal-oral route, aerosolized droplets, or exposure to infected tissue or blood.

The virus is capable of infecting multiple organ systems; however, most infections are asymptomatic. Adenovirus is often cultured from the pharynx and stool of asymptomatic children, and most adults have measurable titers of anti-adenovirus antibodies, implying prior infection. Adenovirus is known to be oncogenic in rodents but not in humans.

Adenovirus has been associated with both sporadic and epidemic disease and, with regard to infections among military recruits, who were routinely immunized against types 4 and 7 from 1971 until the cessation of vaccine production in 1996. Adenovirus became a significant cause of economic cost and morbidity in this setting. A live oral vaccine against adenovirus types 4 and 7 was approved for use in this population by the US Food and Drug Administration (FDA) in 2011, and subsequent incidence of acute respiratory disease declined.

Of interest is the role of adenoviruses as viral vectors in vaccination and in gene therapy.For example, in viral vector vaccines against SARS-CoV2, the vector virus is used to deliver RNA encoding SARS-CoV2 spike protein into target cells. [1, 2, 3] Adenoviruses can infect various cells, both proliferating and quiescent, and thus hold the promise of targeting many different tissues and diseased cell lines.

The genome of adenovirus is well known and can be modified with relative ease to induce lysis or cytotoxicity of a specified cell line without affecting others.

The virus itself can be engineered to remove its replicative capacity by removing essential genes. Additionally, specific genes can be inserted into the virus that then can repair defective metabolic, enzymatic, or synthetic pathways in the host. Suicide gene systems that convert nontoxic systemically delivered prodrugs to active chemotherapeutic agents have been delivered via adenoviral vectors directly into cancer cells. However, the greatest challenge in viral gene therapy, as might be expected, is the immune response to the viral vector itself.

The complex mechanisms by which viral vectors may be incorporated into gene therapy and the rapid growth in this field put further discussion beyond the scope of this text.


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