Adenoviridae
The Adenoviridae family ( v. gr αδένας, gland ') includes non-enveloped viruses with a double-stranded, linear DNA as a genome. Your capsid has an icosahedral symmetry and a special, the virus family characterizing construction of so-called penton and hexon capsomeres. At the pentons typical antenna-like fiber proteins are anchored, give the virions of the family their " satellite -like " appearance. The family currently includes 47 human and animal pathogenic species with numerous subtypes in mammals, birds, reptiles and fish. In humans, the human adenoviruses primarily cause respiratory diseases.
The first adenoviruses were isolated in 1953 by a working group led by Wallace P. Rowe of the tonsils and others ( adenoid ) glandular tissue and grown in cell culture. In the history of molecular biology Adenoviridae play an important role, since with them in 1977 a fundamental process of gene expression was detected, the so-called splicing. In genetic engineering and virological research adenoviruses are for the smuggling of DNA as a viral vector in cells and organisms of some importance.
Morphology
The non-enveloped capsids Adenoviridae are between 70 and 90 nm in diameter and consist of 252 capsomeres. Of these capsomeres are two different types: the so-called Pentone 12 and 240 of the hexons. The hexons (8-10 nm ) consist of a trimer of the hexon protein (viral protein II, molecular mass 120 kDa) and with members of the genus Mastadenovirus by further hexonassoziierte proteins at their contact points stabilized (VP IX, X, XI). There are two other proteins ( VP VI and VIII), which interact simultaneously with proteins of the inner nucleoprotein complex on the inside of hexons. The VP VI is located in an annular arrangement only on the five Hexonen, which are each mounted to a Penton.
The Pentone are located at the corners of the icosahedral symmetry ( the axis points of the five-rayed symmetry axis) and consist of a pentamer of the penton base protein ( VP III, 80 kDa ) and the penton base associated protein ( VP IIIa, 66 kDa). At the pentons set which, depending on the species from 9 to 77.5 nm long fibers ( spikes ), which consists of trimers of the glycosylated fiber protein (VP IV, 62 kDa) are composed. Within the genus Aviadenovirus the fibers consist of two different fiber proteins.
The fiber protein mediates binding to the surface of the host cell and inducing the group-specific antibodies. May enveloped a disadvantage of non-enveloped viruses to the adenoviruses therefore due to the fiber structure deal: An adaptation to a new host or a new target cell (so that a new receptor) can realize non-enveloped viruses usually only by their extreme mutations capsid proteins; However, these mutations may lead to instability of the capsid or the complete loss of its packaging capability. The adenoviruses, however, have the opportunity to develop new variants solely by mutations of the fiber structures and to maintain unchanged the complex capsid.
The interior ( core) of the adenoviruses is filled from a nucleoprotein composed of the double-stranded, linear DNA genome, to which the basic protein VP VII and X ( of the genus Mastadenovirus addition VP V) are attached. Additionally situated on both 5'- ends of the dsDNA a covalently linked protein called terminal protein (TP).
, The genome is from 26 to 45 kbp long and contains repetitive sequences at both ends, the so-called ITR ( inverted terminal repeats ). Within the family is the central portion of the genome that encodes mainly for the structural proteins of the capsid, very conserved. The species, however, differ substantially in the DNA sequence and the gene products at the ends of the genome.
Structure of the adenoviruses
Schematic drawing of an adenovirus
Genome of adenoviruses
System
- Genus Mastadenovirus inter alia, the major human adenoviruses AF in humans, and adenoviruses in cattle, horse, pig, Tupaia, monkeys and guinea pig (Guinea Pig Adenovirus )
- Genus Aviadenovirus inter alia, the Geflügeladenoviren AE, AdV in geese, ducks, pigeons
- Genus Atadenovirus Adenoviruses in cattle, opossum, sheep, deer, bearded dragons, chameleon, gecko and the duck
- Genus Siadenovirus Froschadenovirus 1
- Truthahnadenovirus A
- Chimpanzee adenovirus
- White sturgeon adenovirus: Adenovirus of the White Sturgeon ( Genus possible: Ichtadenovirus )
Similarities to other viruses
The phage PRD1 (Family Tectiviridae ) shows the structure of the capsid and the tail fibers striking similarities with adenoviruses. The arrangement of certain genes on the genome of this phage ( DNA polymerase, terminal protein ) and the presence of two ITRs ( inverted terminal repeats ) shows similarities, which indicates a total of a phylogenetic relation with the adenoviruses.
In plants and fungi can be found partly in the cytoplasm or in the mitochondria, a linear plasmid (e.g., the "killer plasmid" yeast ) which shows a similar arrangement of the genes for the ITRs, the polymerase and terminal protein.
The tail fibers of many members of the Adenoviridae and the Coxsackievirus B use the same receptor CAR ( Coxsackie - adenovirus receptor ) for the recognition of target cells. In addition, the adenoviral tail fibers have structural similarities with a attachment protein within the Reoviridae.
Gene Therapy
Human adenoviruses (especially type 1 from the species C) are a very widespread and popular gene therapy vector. Especially in cancer therapy, adenoviral vectors are used.
Health effects in humans
Human adenoviruses cause a variety of different diseases. The different species ( AG) of the adenoviruses are not unique to a disease. The diseases that are triggered by human adenoviruses can range from mild to severe respiratory infections, disseminated infections in immunocompromised children about, as also diarrhea. Above all, the human adenovirus (type 19) Keratokonjunctivitiden is known ( Augenentzüdung involving the cornea) trigger. According to a U.S. study, the adenovirus is causing 36 human adipose tissue to to turn into particularly large fat cells, causing an obesity can be caused.