Picornavirus
The Picornaviridae family includes non-enveloped viruses with a single-stranded, linear RNA with positive polarity as genome. The viruses of this family include a size of 22-30 nm of the smallest viruses, which led to the naming pico (Latin for very small) and rna for the genome.
Picornaviruses occur in a variety of vertebrates and cause very different diseases, such as a harmless cold, diarrhea, mucosal inflammation or central nervous system infections. The numerous species of picornaviruses are typically divided into many subtypes, since they are characterized by a large surface variance and the associated antigenic variability; so far about 370 types were classified. Important members of the Picornaviridae, for example, in humans, poliovirus, hepatitis A virus, the genus of rhinoviruses and coxsackie viruses in animals, the foot- and - mouth disease virus.
Morphology
The virions of the Picornaviridae have a round shape and are about 22-30 nm in diameter in size. They consist of a non-enveloped, icosahedral capsid is built up of four viral proteins VP1, VP2, VP3 and VP4. In some viral species, there is a protein precursor VP0 contained in small amounts in the capsid, by proteolytic cleavage resulting from the particle during the maturation of the proteins VP2 and VP4. The four structural proteins VP1 -4 together form a capsomere, in which the VP4 lining the inner Kapsidseite and associated through its positively charged amino acid residues with the viral RNA. In a picornavirus capsid be stored for 60 capsomeres together to an icosahedral (T = 1). The surface of the virion is formed only by the three proteins VP1 -3, so that only they are responsible for the antigenic properties and the classification into serotypes.
The picornaviruses are due to the absence of a viral envelope very stable to alcohols ( ethanol, 2- propanol ) and mild detergents ( soap). The species of the genera Enterovirus and Hepatovirus are also stable in the presence of strong detergents and prolonged at pH values below 3.0, which gives them an exceptional environmental resistance. Because of this acid stability, the viruses of these two genera are not inactivated by the acidic environment in the stomach; Therefore, the infection of these viruses is mainly through the digestive tract, from which they can reach other target organs ( CNS, lungs). All other acid-labile picornaviruses infect by droplet and contact infection favors the nasopharyngeal space.
The viral genome consists of a single-stranded RNA of positive polarity. The length of the RNA varies between genres of 7.2 ( rhinovirus ) to 8.5 ( Aphthovirus ) kB. Between two non-coding regions at 3'-and 5' - end of a single open reading frame (ORF) is a viral precursor polyprotein, which is not cleaved during the translation in the individual viral proteins. At the 3 ' end is a typical for positivsträngige RNA virus poly -A tail. The RNA portion at the 5 ' end in front of the start codon is folded by a number of base pairs within the RNA molecule to form a complex secondary structure which functionally shows the activity of an IRES ( internal ribosomal entry site ). This structure is the initiation of translation at the ribosomes and was first described in picornaviruses.
System
- Order Picornavirales
- Family Picornaviridae
- Genus Enterovirus
- Genus Rhinovirus
- Genus Cardio virus
- Genus aphthovirus
- Genus Hepatovirus
- Genus Parechovirus
- Genus Erbovirus
- Genus Kobuvirus
- Genus teschovirus
- Genus Avihepatovirus
- Genus Sapelovirus
- Genus Senecavirus
- Genus Tremovirus
For the virus family Picornaviridae virus species are also expected, but not yet assigned to the genus:
- Species acid - stable equine picornavirus ( EqPV )
- Avian species Entero -like virus 2 ( älv -2)
- Avian species Entero -like virus 3 ( älv -3)
- Avian species Entero -like virus 4 ( älv -4)
- Species avian nephritis virus 3 ( ANV -3)
- Species barramundi virus ( BaV ) ( barramundi, Lates species )
- Cockatoo species Entero -like virus ( CELV )
- Species duck hepatitis virus type 1 (DHV -1)
- Species duck hepatitis virus 3 (DHV -3)
- Species Transmissible guinea fowl enteritis virus ( GTEV )
- Species picorna -like virus of the seal ( SPLV )
- Species sea bass virus 1 (SBV )
- Species Sikhote- Alyn -Virus (SAV )
- Species stint virus 1 (SMV -1) ( smelts, Osmerus genus )
- Species stint virus 2 (SMV -2)
- Species Syr Daria Valley fever virus ( sdfv )
- Species Entero -like virus of turkey ( TELV )
- Species turkey hepatitis virus ( THV )
- Species turkey Pseudoenterovirus 1 ( TPEV -1)
- Species turkey Pseudoenterovirus 2 ( TPEV -2)
The Picornaviridae family shares many characteristics, such as the Kapsidarchitektur, genomic organization and phylogenetically related viral proteins with other viral families. The totality of these similar virus groups have been called the picornavirus super-group. From this group is a new virus order, Picornavirales emerge.