Aphthovirus
Encyclopedia
Aphthovirus is a viral
genus of the family Picornaviridae. Aphthoviruses infect vertebrate
s, and include the causative agent of foot-and-mouth disease
. Foot-and-mouth disease virus
(FMDV) is the prototypic member of the genus Aphthovirus. There are seven FMDV serotype
s: A, O, C, SAT 1, SAT 2, SAT 3 and Asia 1 belonging to the species FMDV, and two non-FMDV serotypes, the species Bovine rhinitis B virus (BRBV) and Equine rhinitis A virus (ERAV).
and have an icosahedral nucleocapsid
with a diameter of around 27 to 30 nm. The aphthoviruses are differentiated from other picornavirus
es as they have a larger genome
(ca. 8.2 kilobases.) The genome is linear and non-segmented. It consists of a single molecule of (+) sense RNA, with a 5' genome linked protein (VPg
), which is associated to the genome via a phosphodiester bond
linked to a tyrosine
residue. The 5' end
of the genome has a 'poly C' region, while the 3' end
is polyadenylated
http://www.ncbi.nlm.nih.gov/ICTVdb/ICTVdB/00.052.0.05.htm.
The virions consist of a non-enveloped virus capsid
, which is round and displays icosahedral
symmetry.
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
.
Aphthoviruses include the causative agents of foot-and-mouth disease
(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 Europe, 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
.
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.
Virus
A virus is a small infectious agent that can replicate only inside the living cells of organisms. Viruses infect all types of organisms, from animals and plants to bacteria and archaea...
genus of the family Picornaviridae. Aphthoviruses infect vertebrate
Vertebrate
Vertebrates are animals that are members of the subphylum Vertebrata . Vertebrates are the largest group of chordates, with currently about 58,000 species described. Vertebrates include the jawless fishes, bony fishes, sharks and rays, amphibians, reptiles, mammals, and birds...
s, and include the causative agent of foot-and-mouth disease
Foot-and-mouth disease
Foot-and-mouth disease or hoof-and-mouth disease is an infectious and sometimes fatal viral disease that affects cloven-hoofed animals, including domestic and wild bovids...
. Foot-and-mouth disease virus
Foot-and-mouth disease virus
The foot-and-mouth disease virus is the pathogen that causes foot-and-mouth disease. It is a picornavirus, the prototypical member of the Aphthovirus genus...
(FMDV) is the prototypic member of the genus Aphthovirus. There are seven FMDV serotype
Serotype
Serotype or serovar refers to distinct variations within a subspecies of bacteria or viruses. These microorganisms, viruses, or cells are classified together based on their cell surface antigens...
s: A, O, C, SAT 1, SAT 2, SAT 3 and Asia 1 belonging to the species FMDV, and two non-FMDV serotypes, the species Bovine rhinitis B virus (BRBV) and Equine rhinitis A virus (ERAV).
Morphology and genome structure
Aphthoviruses are non-envelopedViral envelope
Many viruses have viral envelopes covering their protein capsids. The envelopes typically are derived from portions of the host cell membranes , but include some viral glycoproteins. Functionally, viral envelopes are used to help viruses enter host cells...
and have an icosahedral nucleocapsid
Capsid
A capsid is the protein shell of a virus. It consists of several oligomeric structural subunits made of protein called protomers. The observable 3-dimensional morphological subunits, which may or may not correspond to individual proteins, are called capsomeres. The capsid encloses the genetic...
with a diameter of around 27 to 30 nm. The aphthoviruses are differentiated from other picornavirus
Picornavirus
A picornavirus is a virus belonging to the family Picornaviridae. Picornaviruses are non-enveloped, positive-stranded RNA viruses with an icosahedral capsid. The genome RNA is unusual because it has a protein on the 5' end that is used as a primer for transcription by RNA polymerase...
es as they have a larger genome
Genome
In modern molecular biology and genetics, the genome is the entirety of an organism's hereditary information. It is encoded either in DNA or, for many types of virus, in RNA. The genome includes both the genes and the non-coding sequences of the DNA/RNA....
(ca. 8.2 kilobases.) The genome is linear and non-segmented. It consists of a single molecule of (+) sense RNA, with a 5' genome linked protein (VPg
VPg
VPg is a protein attached to the 5' end of RNA during RNA synthesis in a wide variety of viruses including Picornaviridae such as Foot-and-mouth disease and poliovirus . VPg stands for "viral protein genome-linked".-Attachment during RNA synthesis:...
), which is associated to the genome via a phosphodiester bond
Phosphodiester bond
A phosphodiester bond is a group of strong covalent bonds between a phosphate group and two 5-carbon ring carbohydrates over two ester bonds. Phosphodiester bonds are central to all known life, as they make up the backbone of each helical strand of DNA...
linked to a tyrosine
Tyrosine
Tyrosine or 4-hydroxyphenylalanine, is one of the 22 amino acids that are used by cells to synthesize proteins. Its codons are UAC and UAU. It is a non-essential amino acid with a polar side group...
residue. The 5' end
Directionality (molecular biology)
Directionality, in molecular biology and biochemistry, is the end-to-end chemical orientation of a single strand of nucleic acid. The chemical convention of naming carbon atoms in the nucleotide sugar-ring numerically gives rise to a 5′-end and a 3′-end...
of the genome has a 'poly C' region, while the 3' end
Directionality (molecular biology)
Directionality, in molecular biology and biochemistry, is the end-to-end chemical orientation of a single strand of nucleic acid. The chemical convention of naming carbon atoms in the nucleotide sugar-ring numerically gives rise to a 5′-end and a 3′-end...
is polyadenylated
Polyadenylation
Polyadenylation is the addition of a poly tail to an RNA molecule. The poly tail consists of multiple adenosine monophosphates; in other words, it is a stretch of RNA that has only adenine bases. In eukaryotes, polyadenylation is part of the process that produces mature messenger RNA for translation...
http://www.ncbi.nlm.nih.gov/ICTVdb/ICTVdB/00.052.0.05.htm.
The virions consist of a non-enveloped virus capsid
Capsid
A capsid is the protein shell of a virus. It consists of several oligomeric structural subunits made of protein called protomers. The observable 3-dimensional morphological subunits, which may or may not correspond to individual proteins, are called capsomeres. The capsid encloses the genetic...
, which is round and displays icosahedral
Icosahedron
In geometry, an icosahedron is a regular polyhedron with 20 identical equilateral triangular faces, 30 edges and 12 vertices. It is one of the five Platonic solids....
symmetry.
Replication, ecology and pathology
Aphthoviruses replicate in a similar fashion to all picornavirusPicornavirus
A picornavirus is a virus belonging to the family Picornaviridae. Picornaviruses are non-enveloped, positive-stranded RNA viruses with an icosahedral capsid. The genome RNA is unusual because it has a protein on the 5' end that is used as a primer for transcription by RNA polymerase...
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
Lysis refers to the breaking down of a cell, often by viral, enzymic, or osmotic mechanisms that compromise its integrity. A fluid containing the contents of lysed cells is called a "lysate"....
.
Aphthoviruses include the causative agents of foot-and-mouth disease
Foot-and-mouth disease
Foot-and-mouth disease or hoof-and-mouth disease is an infectious and sometimes fatal viral disease that affects cloven-hoofed animals, including domestic and wild bovids...
(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 Europe, 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
Vaccine
A vaccine is a biological preparation that improves immunity to a particular disease. A vaccine typically contains an agent that resembles a disease-causing microorganism, and is often made from weakened or killed forms of the microbe or its toxins...
.
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.
External links
- Aphthovirus summary from the Iziko Museums of Cape Town, South Africa.
- Foot-and-Mouth Disease summary from the US Department of Agriculture.
- Aphthovirus
- Animal viruses
- Viralzone: Aphtovirus