Adenoviridae(redirected from Adenovirus early proteins)
Also found in: Medical.
A family of viral agents associated with pharyngoconjunctival fever, acute respiratory disease, epidemic keratoconjunctivitis, and febrile pharyngitis in children. A number of types have been isolated from tonsils and adenoids removed from surgical patients. Although most of the illnesses caused by adenoviruses are respiratory, adenoviruses are frequently excreted in stools, and certain adenoviruses have been isolated from sewage. Distinct serotypes of mammalian and avian species are known. These genera contain 87 and 14 species, respectively. See Animal virus
Infective virus particles, 70 nanometers in diameter, are icosahedrons with shells (capsids) composed of 252 subunits (capsomeres). No outer envelope is known. The genome is double-stranded deoxyribonucleic acid (DNA), with a molecular weight of 20–25 × 106. Three major soluble antigens are separable from the infectious particle by differential centrifugation. These antigens—a group-specifc antigen common to all adenovirus types, a type-specific antigen unique for each type, and a toxinlike material which also possesses group specificity—represent virus structural protein subunits that are produced in large excess of the amount utilized for synthesis of infectious virus.
The known types of adenoviruses of humans total at least 33, and previously unrecognized types continue to be isolated. The serotypes are antigenically distinct in neutralization tests, but they share a complement-fixing antigen, which is probably a smaller soluble portion of the virus.
The virus does not commonly produce acute disease in laboratory animals but is cytopathogenic, that is, destroys cells, in cultures of human tissue. Certain human adenovirus serotypes produce cancer when injected into newborn hamsters.
Base ratio determinations have revealed three distinct groups of adenoviruses: those with a low guanine plus cytosine (G + C) content (48–49%); those with an intermediate G + C content (50–53%); and those with a high G + C content (56–60%). The strongly oncogenic adenovirus types 12, 18, and 31 are the only members of the group with low G + C, and certain adenoviruses in the intermediate group (types 3, 7, 14, 16, and 21) are mildly oncogenic. The adenovirus mRNA observed in transformed and tumor cells has a G + C content of 50–52% in the DNA. This suggests that viral DNA regions containing 47–48% G + C are integrated into the tumor cells or that such regions are preferentially transcribed. However, the mRNA from tumor cells induced by one subgroup such as the highly oncogenic adenoviruses (types 12 and 18) do not hybridize with DNA from the other two subgroups. Apparently, different viralcoded information is involved in carcinogenesis by the three different groups of adenoviruses.
With simian adenovirus 7 (SA7), the intact genome, as well as the heavy and light halves of the viral DNA, is capable of inducing tumors when injected into newborn hamsters. Extensive studies have failed to demonstrate adenovirus DNA or viral-specific mRNA in human tumors.
Live virus vaccines against type 4 and type 7 have been developed and used extensively in military populations. When both are administered simultaneously, vaccine recipients respond with neutralizing antibodies against both virus types. See Antigen, Complement-fixation test, Neutralization reaction (immunology), Virus classification