''Aphthovirus'' (from the Greek -, vesicles in the mouth) is a viral genus of the family ''

Picornaviridae Picornaviruses are a group of related nonenveloped RNA viruses which infect vertebrates including fish, mammals, and birds. They are viruses that represent a large family of small, positive-sense, single-stranded RNA viruses with a 30 ...

''. Aphthoviruses infect split-hooved animals, and include the causative agent of

foot-and-mouth disease Foot-and-mouth disease (FMD) or hoof-and-mouth disease (HMD) is an infectious and sometimes fatal viral disease that affects cloven-hoofed animals, including domestic and wild bovids. The virus causes a high fever lasting two to six days, follo ...

, '' Foot-and-mouth disease virus'' (FMDV). There are seven FMDV

serotype A serotype or serovar is a distinct variation within a species of bacteria or virus or among immune cells of different individuals. These microorganisms, viruses, or cells are classified together based on their surface antigens, allowing the ep ...

s: A, O, C, SAT 1, SAT 2, SAT 3 and Asia 1, and four non-FMDV serotypes belonging to three additional species ''Bovine rhinitis A virus'' (BRAV), ''Bovine rhinitis B virus'' (BRBV) and ''Equine rhinitis A virus'' (ERAV).

Structure

Aphthoviruses are

non-enveloped A viral envelope is the outermost layer of many types of viruses. It protects the genetic material in their life cycle when traveling between host cells. Not all viruses have envelopes. Numerous human pathogenic viruses in circulation are encas ...

and have an icosahedral

capsid A capsid is the protein shell of a virus, enclosing its genetic material. It consists of several oligomeric (repeating) structural subunits made of protein called protomers. The observable 3-dimensional morphological subunits, which may or ma ...

with a diameter of around 27 to 30 nm. The assembled viral capsid contains a single copy of the RNA genome and 60

copies Copy may refer to: *Copying or the product of copying (including the plural "copies"); the duplication of information or an artifact **Cut, copy and paste, a method of reproducing text or other data in computing **File copying **Photocopying, a pr ...

of the four viral capsid proteins VP1, VP2, VP3, and VP4. The protomers form the sides of the icosahedral capsid. The VP4 protein is internal.

Genome

The aphthoviruses are differentiated from other

picornavirus Picornaviruses are a group of related nonenveloped RNA viruses which infect vertebrates including fish, mammals, and birds. They are viruses that represent a large family of small, positive-sense, single-stranded RNA viruses with a 30 nm ...

es as they have a larger

genome In the fields of molecular biology and genetics, a genome is all the genetic information of an organism. It consists of nucleotide sequences of DNA (or RNA in RNA viruses). The nuclear genome includes protein-coding genes and non-coding ...

(7.5–8.5

kilobase A base pair (bp) is a fundamental unit of double-stranded nucleic acids consisting of two nucleobases bound to each other by hydrogen bonds. They form the building blocks of the DNA double helix and contribute to the folded structure of both DN ...

s). The genome is non-segmented and consists of a positive-sense single-stranded RNA. It contains a single

open reading frame In molecular biology, open reading frames (ORFs) are defined as spans of DNA sequence between the start and stop codons. Usually, this is considered within a studied region of a prokaryotic DNA sequence, where only one of the six possible readi ...

with a

5' end Directionality, in molecular biology and biochemistry, is the end-to-end chemical orientation of a single strand of nucleic acid. In a single strand of DNA or RNA, the chemical convention of naming carbon atoms in the nucleotide pentose-sugar- ...

linked protein ( VPg), which is associated with the genome via a

phosphodiester bond In chemistry, a phosphodiester bond occurs when exactly two of the hydroxyl groups () in phosphoric acid react with hydroxyl groups on other molecules to form two ester bonds. The "bond" involves this linkage . Discussion of phosphodiesters is ...

linked to a

tyrosine -Tyrosine or tyrosine (symbol Tyr or Y) or 4-hydroxyphenylalanine is one of the 20 standard amino acids that are used by cells to synthesize proteins. It is a non-essential amino acid with a polar side group. The word "tyrosine" is from the G ...

residue. The

5' untranslated region The 5′ untranslated region (also known as 5′ UTR, leader sequence, transcript leader, or leader RNA) is the region of a messenger RNA (mRNA) that is directly upstream from the initiation codon. This region is important for the regulation of ...

(UTR) of the genome contains a poly(C) tract and an

internal ribosome entry site An internal ribosome entry site, abbreviated IRES, is an RNA element that allows for translation initiation in a cap-independent manner, as part of the greater process of protein synthesis. In eukaryotic translation, initiation typically occurs at ...

(IRES), while the

3' UTR In molecular genetics, the three prime untranslated region (3′-UTR) is the section of messenger RNA (mRNA) that immediately follows the translation termination codon. The 3′-UTR often contains regulatory regions that post-transcriptionally ...

is polyadenylated. The P1 region encodes the structural proteins. The P2 and P3 regions encode the nonstructural proteins associated with replication.

Replication

Aphthoviruses replicate in a similar fashion to all

es. Replication is cytoplasmic and initially involves attachment of the exogenous virus to the cell membrane. Attachment to the membrane and subsequent entry into the cell is mediated by a membrane receptor. After genome replication within the cytoplasm, virion assembly occurs and new virus particles aggregate within the cell. Release of virus particles is mediated by

cell lysis Lysis ( ) is the breaking down of the membrane of a cell, often by viral, enzymic, or osmotic (that is, "lytic" ) mechanisms that compromise its integrity. A fluid containing the contents of lysed cells is called a ''lysate''. In molecular bio ...

Recombination

The aphthovirus RNA

is able to undergo

genetic recombination Genetic recombination (also known as genetic reshuffling) is the exchange of genetic material between different organisms which leads to production of offspring with combinations of traits that differ from those found in either parent. In eukaryo ...

. Recombination occurs at a large number of genomic sites indicating that RNA recombination in aphthovirus is a general, rather than a site specific, phenomenon.

Pathology and ecology

Aphthoviruses include the causative agents of

(FMD), which primarily affects livestock such as cattle, swine, sheep and goats. FMD was first discovered in Italy in the 16th century. Since then, the prevalence of the disease has remained, despite many countries being declared FMD-free. Endemic regions of the disease include areas of Africa, Asia and South America. The virus commonly persists in animal feed and is able to survive environmentally for up to one month. Eradication of FMD in endemic areas has been difficult, despite the availability of a

vaccine A vaccine is a biological preparation that provides active acquired immunity to a particular infectious or malignant disease. The safety and effectiveness of vaccines has been widely studied and verified.

. Equine rhinitis A virus (ERAV) was first isolated from horses in the 1960s and 1970s showing acute febrile respiratory disease signs, including fever, cough, clear nasal discharge and lethargy. Given its similarity to the common cold in humans (caused by another picornavirus, rhinovirus), ERAV was initially named "equine rhinovirus 1". Modern molecular biology techniques such as nucleotide sequencing demonstrated that ERAV was in fact more closely related to FMDV, and was reclassified to the genus ''Aphthovirus''.

References

External links

''Aphthovirus'' summary
from the Iziko Museums of Cape Town, South Africa.

from the US Department of Agriculture.

ICTV
{{Taxonbar, from=Q618549 Virus genera