Adenovirus

Introduction Adenoviruses can replicate and produce disease in the respiratory, gastrointestinal, and urinary tracts and in the eye. Many adenovirus infections are subclinical, and virus may persist in the host for months. About one-third of the 51 known human serotypes are responsible for most cases of human adenovirus disease. A few types serve as models for cancer induction in animals. Adenoviruses are especially valuable systems for molecular and biochemical studies of eukaryotic cell processes (gene delivery vehicle).

Properties of Adenoviruses Important Properties of Adenoviruses Virion: Icosahedral, 70–90 nm in diameter, 252 capsomeres; fiber projects from each vertex Composition: DNA (13%), protein (87%) Genome: Double-stranded DNA, linear, 26–45 kbp, protein-bound to termini, infectious Proteins: Important antigens (hexon, penton base, fiber) are associated with the major outer capsid proteins Envelope: None Replication: Nucleus Outstanding characteristic: Excellent models for molecular studies of eukaryotic cell processes

Classification Adenoviruses have been recovered from a wide variety of species and grouped into four genera. All the human adenoviruses are classified in the Mastadenovirus genus. Human adenoviruses are divided into six groups (A–F) on the basis of their genetic, physical, chemical, and biologic properties.

Classification Classification Schemes for Human Adenoviruses Hemaggluthination Oncogenic Potential Group Serotypes Result Percentage of G + Ca in DNA Tumorigenicity In Vivob Transformation of Cells A 12, 18, 31 IV None 48–49 High + B 3, 7, 11, 14, 16, 21, 34, 35, 50 I Monkey (complete) 50–52 Moderate C 1, 2, 5, 6 III Rat (partial) 57–59 Low or none D 8–10, 13, 15, 17, 19, 20, 22–30, 32, 33, 36–39, 42–49, 51 II Rat (complete) 57–61 Low or nonec E 4 57 F 40, 41

Adenovirus Infections in Humans

Pathogenesis In fact, the name "adenovirus" reflects the recovery of the initial isolate from explants of human adenoids. Adenoviruses infect and replicate in epithelial cells Most human adenoviruses replicate in intestinal epithelium after ingestion but usually produce subclinical infections rather than overt symptoms.

Clinical Findings About one-third of the known human serotypes are commonly associated with human illness. Adenoviruses 1–7 are the most common types worldwide and account for most instances of adenovirus-associated illness. . Disease : Respiratory Diseases Eye Infections Gastrointestinal Disease Other Diseases

Respiratory Diseases Typical symptoms include cough, nasal congestion, fever, and sore throat.This syndrome is most commonly manifested in infants and children and usually involves group C viruses. Adenoviruses are responsible for about 5% of acute respiratory disease in young children, but they account for much less in adults Adenoviruses—particularly types 3, 7, and 21, responsible for 10– 20% of pneumonias in childhood. Adenoviral pneumonia reported for 8–10% mortality rate in the very young. Adenoviruses are the cause of an acute respiratory disease syndrome among military recruits. This syndrome is characterized by fever, sore throat, nasal congestion, cough, and malaise, sometimes leading to pneumonia. (types 4 and 7 and occasionally by type 3).

Eye Infections Mild ocular involvement may be part of the respiratory-pharyngeal syndromes caused by adenoviruses. Pharyngoconjunctival fever tends to occur in outbreaks, such as at children's summer camps ("swimming pool conjunctivitis"), and is associated with types 3 and 7. Duration of conjunctivitis is 1–2 weeks A more serious disease is epidemic keratoconjunctivitis. This disease occurs mainly in adults and is highly contagious.

Gastrointestinal Disease However, two serotypes (types 40 and 41) have been etiologically associated with infantile gastroenteritis and may account for 5–15% of cases of viral gastroenteritis in young children. Adenovirus types 40 and 41 are abundantly present in diarrheal stools. The enteric adenoviruses are very difficult to cultivate.

Other Diseases Immunocompromised patients may suffer from a variety of casual and severe adenovirus infections. The most common problem caused by adenovirus infection in transplant patients is respiratory disease that may progress to severe pneumonia and may be fatal (usually types 1–7). Children receiving liver transplants may develop adenovirus hepatitis in the allograft. In addition, children with heart transplants who develop myocardial adenovirus infections are at increased risk of graft loss. Patients with acquired immunodeficiency syndrome (AIDS) may suffer adenovirus infections, especially in the gastrointestinal tract.

Laboratory Diagnosis Detection, Isolation, & Identification of Virus Serology

Treatment There is no specific treatment for adenovirus infections.