''Mammalian orthoreovirus'' (MRV) is a
double-stranded RNA virus
Double-stranded RNA viruses (dsRNA viruses) are a polyphyletic group of viruses that have double-stranded genomes made of ribonucleic acid. The double-stranded genome is used to transcribe a positive-strand RNA by the viral RNA-dependent RNA ...
. It is a part of the family ''
Reoviridae
''Reoviridae'' is a family of double-stranded RNA viruses. Member viruses have a wide host range, including vertebrates, invertebrates, plants, protists and fungi. They lack lipid envelopes and package their segmented genome within multi-layered ...
'', as well as the subfamily ''
Spinareovirinae
''Spinareovirinae'' is a subfamily of double-stranded RNA viruses in the family ''Reoviridae''. Viruses in this group are distinguished by the presence of a turreted protein on the inner capsid. (''Spina'' = spiny or thorny in Latin.)
Taxonomy ...
''. As seen in the name, the Mammalian Ortheoreovirus infects numerous
mammalian species
''Mammalian Species'' is a peer-reviewed scientific journal published by Oxford University Press on behalf of the American Society of Mammalogists. The journal publishes accounts of 12–35 mammal species yearly. The articles summarize the current ...
and vertebrates which serve as natural hosts. Some diseases that occur as a result of this virus or are associated with this virus include mild upper respiratory illness, and gastrointestinal illness. Examples of these are: upper respiratory tract syndromes,
gastroenteritis
Gastroenteritis, also known as infectious diarrhea and gastro, is an inflammation of the gastrointestinal tract including the stomach and intestine. Symptoms may include diarrhea, vomiting, and abdominal pain. Fever, lack of energy, and dehydra ...
(stomach flu),
biliary atresia
Biliary atresia, also known as extrahepatic ductopenia and progressive obliterative cholangiopathy, is a childhood disease of the liver in which one or more bile ducts are abnormally narrow, blocked, or absent. It can be congenital or acquired. I ...
,
obstructive hydrocephalus
Hydrocephalus is a condition in which an accumulation of cerebrospinal fluid (CSF) occurs within the brain. This typically causes increased pressure inside the skull. Older people may have headaches, double vision, poor balance, urinary inco ...
,
jaundice
Jaundice, also known as icterus, is a yellowish or greenish pigmentation of the skin and sclera due to high bilirubin levels. Jaundice in adults is typically a sign indicating the presence of underlying diseases involving abnormal heme meta ...
,
alopecia
Hair loss, also known as alopecia or baldness, refers to a loss of hair from part of the head or body. Typically at least the head is involved. The severity of hair loss can vary from a small area to the entire body. Inflammation or scarri ...
,
conjunctivitis
Conjunctivitis, also known as pink eye, is inflammation of the conjunctiva, outermost layer of the white part of the eye and the inner surface of the eyelid. It makes the eye appear pink or reddish. Pain, burning, scratchiness, or itchiness may ...
, and ‘oily hair’ associated with
steatorrhea
Steatorrhea (or steatorrhoea) is the presence of excess fat in feces. Stools may be bulky and difficult to flush, have a pale and oily appearance, and can be especially foul-smelling. An oily anal leakage or some level of fecal incontinence may oc ...
.
There are four
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 epi ...
s, or distinct variations within the viral species, of Mammalian orthoreovirus. This means that there are four separate strains of Mammalian orthoreovirus: Type 1 Lang, Type 2 Jones, Type 3 Dearing, Type 4 Ndelle. An example of these strains is Mammalian orthoreovirus type 3, or Mammalian orthoreovirus 3-Dearing (MRV-3; Strain Dearing). It induces cell death preferentially in transformed cells and therefore displays inherent oncolytic properties.
It is believed that Mammalian orthoreovirus causes subclinical infection in humans more so than in other mammals. Meaning, that a human infected with Mammalian orthoreovirus, regardless of the
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 epi ...
, is nearly or completely
asymptomatic
In medicine, any disease is classified asymptomatic if a patient tests as carrier for a disease or infection but experiences no symptoms. Whenever a medical condition fails to show noticeable symptoms after a diagnosis it might be considered asy ...
, and therefore, don't exhibit signs or symptoms of the virus. This theory is based upon evidence that the majority of people have
antibodies
An antibody (Ab), also known as an immunoglobulin (Ig), is a large, Y-shaped protein used by the immune system to identify and neutralize foreign objects such as pathogenic bacteria and viruses. The antibody recognizes a unique molecule of the ...
for all of the serotypes, meaning they were exposed to the virus at some point and the body's immune system built an immunity to it after being infected.
Viral classification
![Baltimore Classification](https://upload.wikimedia.org/wikipedia/commons/4/49/Baltimore_Classification.svg)
Based upon the
Baltimore classification
Baltimore classification is a system used to classify viruses based on their manner of messenger RNA (mRNA) synthesis. By organizing viruses based on their manner of mRNA production, it is possible to study viruses that behave similarly as a di ...
scheme, the Mammalian orthoreovirus is a
Group III virus. This is because the Mammalian orthoreovirus is a
double stranded RNA virus, and as stated previously, a part of the
Reovirus
''Reoviridae'' is a family of double-stranded RNA viruses. Member viruses have a wide host range, including vertebrates, invertebrates, plants, protists and fungi. They lack lipid envelopes and package their segmented genome within multi-layered ...
family. The name “Reo-“is derived from ''respiratory enteric orphan diseases''. The term “orphan diseases” makes reference to the fact that some
Reoviruses
''Reoviridae'' is a family of double-stranded RNA viruses. Member viruses have a wide host range, including vertebrates, invertebrates, plants, protists and fungi. They lack lipid envelopes and package their segmented genome within multi-layered ...
were not known to be associated with any diseases at the time of their discovery. The
Reoviridae
''Reoviridae'' is a family of double-stranded RNA viruses. Member viruses have a wide host range, including vertebrates, invertebrates, plants, protists and fungi. They lack lipid envelopes and package their segmented genome within multi-layered ...
family is also characterized with "naked", icosahedral capsids and 10-12 segments of linear
double stranded RNA. “Naked” meaning the icosahedral capsid is not surrounded by a viral envelope.
Within the
Reoviridae
''Reoviridae'' is a family of double-stranded RNA viruses. Member viruses have a wide host range, including vertebrates, invertebrates, plants, protists and fungi. They lack lipid envelopes and package their segmented genome within multi-layered ...
family the Mammalian orthoreovirus is a part of the
Spinareovirinae
''Spinareovirinae'' is a subfamily of double-stranded RNA viruses in the family ''Reoviridae''. Viruses in this group are distinguished by the presence of a turreted protein on the inner capsid. (''Spina'' = spiny or thorny in Latin.)
Taxonomy ...
subfamily. This is based on the fact that viruses within this subfamily, such as the Mammalian
orthoreovirus
''Orthoreovirus'' is a genus of viruses, in the family ''Reoviridae'', in the subfamily ''Spinareovirinae''. Vertebrates serve as natural hosts. There are ten species in this genus. Diseases associated with this genus include mild upper respirato ...
,
Aquareovirus
''Aquareovirus'' is a genus of double-stranded RNA viruses in the family ''Reoviridae'' and subfamily ''Spinareovirinae''. Fish, shellfish, and crustacean species serve as natural hosts. Aquareoviruses in general have low or no pathogenicity for ...
,
Coltivirus
Coltivirus is a genus of viruses (belonging to the ''Reoviridae'' family) that infects vertebrates and invertebrates. It includes the causative agent of Colorado tick fever. Colorado tick fever virus can cause a fever, chills, headache, photopho ...
,
Cypovirus
''Cypovirus'', short for cytoplasmic polyhedrosis virus, is a genus of double-stranded RNA viruses in the family ''Reoviridae'' and subfamily ''Spinareovirinae''. Cypoviruses have only been isolated from insects. Diseases associated with this ge ...
, etc., have the presence of a turreted protein on the inner capsid.
History
![Reovirus phylogenetics](https://upload.wikimedia.org/wikipedia/commons/6/6f/Reovirus_phylogenetics.jpg)
The etymology of the Mammalian orthoreovirus is based upon “ortho-“ translated from Greek as “straight” and “reovirus“ from respiratory enteric orphan virus.
The Mammalian orthoreovirus was labeled an orphan virus in the 1950s when it was discovered. It was described as a “ubiquitous presence” in
mammal
Mammals () are a group of vertebrate animals constituting the class Mammalia (), characterized by the presence of mammary glands which in females produce milk for feeding (nursing) their young, a neocortex (a region of the brain), fur or ...
s meaning it was found virtually everywhere. Serum surveys conducted in the 1950s found neutralizing antibodies to mammalian orthoreovirus in
human
Humans (''Homo sapiens'') are the most abundant and widespread species of primate, characterized by bipedalism and exceptional cognitive skills due to a large and complex brain. This has enabled the development of advanced tools, culture, ...
s,
monkey
Monkey is a common name that may refer to most mammals of the infraorder Simiiformes, also known as the simians. Traditionally, all animals in the group now known as simians are counted as monkeys except the apes, which constitutes an incomple ...
s,
rabbit
Rabbits, also known as bunnies or bunny rabbits, are small mammals in the family Leporidae (which also contains the hares) of the order Lagomorpha (which also contains the pikas). ''Oryctolagus cuniculus'' includes the European rabbit speci ...
s and
guinea pig
The guinea pig or domestic guinea pig (''Cavia porcellus''), also known as the cavy or domestic cavy (), is a species of rodent belonging to the genus ''Cavia'' in the family Caviidae. Breeders tend to use the word ''cavy'' to describe the ani ...
s. More recent studies suggest that MRV is still a ubiquitous presence in
human
Humans (''Homo sapiens'') are the most abundant and widespread species of primate, characterized by bipedalism and exceptional cognitive skills due to a large and complex brain. This has enabled the development of advanced tools, culture, ...
s. The Mammalian orthoreovirus is well researched and understood on the biochemical and structural levels, additionally their pathogenesis in mice serves as a model system for studying the pathogenesis of the reoviruses in general. The Orthoreovirus genus is subdivided into fusogenic and non-fusogenic. The division is based upon fusogenic orthoreoviruses having the ability to cause fusion of infected cells, resulting in multinucleated cellular syncytia. These fusogenic orthoreoviruses encode a fusion-associated small transmembrane (FAST) protein that is plays a role in this ability. Prototypical Mammailian orthoreovirsus are non-fusogenic, and do not produce syncytia because of the lack of the fusion-associated transmembrane protein.
The Mammalian orthoreovirus serotypes have been studied significantly at the antigenetic and sequence levels. Serotypes 1 (Lang), 2 (Jones), and 3 (Dearing) were originally recognized based upon virus neutralization and hemaglutination-inhibition profiles. Serotype 4 (Ndelle) have been studied at the antigenetic and molecular levels.
Structure and genome
Just as the rest of the reoviruses are structured, the Mammalian orthoreovirus contains a segmented genome with a linear genomic arrangement, which is enclosed in a 70-80 nm double layered protein
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 may ...
, made up of an inner (T=2) and outer layer (T=13). The
viral core
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 may ...
of MRV, and
orthoreoviruses alike, consist of an inner
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 may ...
layer plus its enclosed viral
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 ge ...
. The Mammalian orthoreovirus
double stranded RNA 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 ge ...
contains 10 segments divided into three size classes (small, medium, and large) based upon their characteristic mobility during gel electrophoresis. The genome has three large segments, (L1, L2, and L3) which encode for λ (lambda) proteins; three medium segments (M1, M2, and M3) that encode for μ (mu) proteins; and four small segments (S1, S2, S3, and S4) which encode for σ (sigma) proteins. In total, the genome size is approximately 23,500 base pairs.
![Structure of the reovirus virion](https://upload.wikimedia.org/wikipedia/commons/1/11/Structure_of_the_reovirus_virion.png)
Generally, these
double stranded RNA genome segments contain a single gene encoding a single protein, although there are some exceptions. The S1 genome segment of the non-fusogenic reoviruses (e.g., Mammalian orthoreovirus) encode the σ1 cell attachment protein. Contained with the σ1 gene is a second, smaller open reading frame encoding the non-structural protein σ1s.
Reovirus
''Reoviridae'' is a family of double-stranded RNA viruses. Member viruses have a wide host range, including vertebrates, invertebrates, plants, protists and fungi. They lack lipid envelopes and package their segmented genome within multi-layered ...
double stranded RNA, cannot serve as a template for protein translation or as messenger RNA (
mRNA
In molecular biology, messenger ribonucleic acid (mRNA) is a single-stranded molecule of RNA that corresponds to the genetic sequence of a gene, and is read by a ribosome in the process of Protein biosynthesis, synthesizing a protein.
mRNA is ...
). Because of the nature of
double stranded RNA, double stranded RNA viruses such as
reoviruses
''Reoviridae'' is a family of double-stranded RNA viruses. Member viruses have a wide host range, including vertebrates, invertebrates, plants, protists and fungi. They lack lipid envelopes and package their segmented genome within multi-layered ...
, and the Mammalian orthoreovirus must carry and/or encode the necessary
enzyme
Enzymes () are proteins that act as biological catalysts by accelerating chemical reactions. The molecules upon which enzymes may act are called substrates, and the enzyme converts the substrates into different molecules known as products. A ...
s within their
virions
A virus is a submicroscopic infectious agent that replicates only inside the living cells of an organism. Viruses infect all life forms, from animals and plants to microorganisms, including bacteria and archaea.
Since Dmitri Ivanovsky's 1 ...
in order to first
transcribe
Transcription refers to the process of converting sounds (voice, music etc.) into letters or musical notes, or producing a copy of something in another medium, including:
Genetics
* Transcription (biology), the copying of DNA into RNA, the fir ...
their
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 ge ...
, producing
mRNA
In molecular biology, messenger ribonucleic acid (mRNA) is a single-stranded molecule of RNA that corresponds to the genetic sequence of a gene, and is read by a ribosome in the process of Protein biosynthesis, synthesizing a protein.
mRNA is ...
, and delivering their infectious
mRNA
In molecular biology, messenger ribonucleic acid (mRNA) is a single-stranded molecule of RNA that corresponds to the genetic sequence of a gene, and is read by a ribosome in the process of Protein biosynthesis, synthesizing a protein.
mRNA is ...
into the
cytoplasm
In cell biology, the cytoplasm is all of the material within a eukaryotic cell, enclosed by the cell membrane, except for the cell nucleus. The material inside the nucleus and contained within the nuclear membrane is termed the nucleoplasm. The ...
of the host cell. The double stranded RNA
viral core
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 may ...
, which plays an important role in packaging the genome and the
transcription
Transcription refers to the process of converting sounds (voice, music etc.) into letters or musical notes, or producing a copy of something in another medium, including:
Genetics
* Transcription (biology), the copying of DNA into RNA, the fir ...
of
mRNA
In molecular biology, messenger ribonucleic acid (mRNA) is a single-stranded molecule of RNA that corresponds to the genetic sequence of a gene, and is read by a ribosome in the process of Protein biosynthesis, synthesizing a protein.
mRNA is ...
as well as maturation, contain proteins which are present across the entire
Type 3 double stranded RNA group. In the outer capsid layer, the proteins take part in the role of environmental stability, and cell attachment to a number of hosts, which are quite variable even within the same
Orthoreovirus
''Orthoreovirus'' is a genus of viruses, in the family ''Reoviridae'', in the subfamily ''Spinareovirinae''. Vertebrates serve as natural hosts. There are ten species in this genus. Diseases associated with this genus include mild upper respirato ...
genus.
The internal structure of MRV has been fully reconstructed. λ3 is the RNA replicase, whereas µ2 is a transcription factor.
Replication cycle
As stated in the beginning of the article, the natural hosts of the Mammalian orthoreovirus are
mammal
Mammals () are a group of vertebrate animals constituting the class Mammalia (), characterized by the presence of mammary glands which in females produce milk for feeding (nursing) their young, a neocortex (a region of the brain), fur or ...
s, ranging from pigs to humans, and the majority of all mammalian species. This is why the Mammalian orthoreovirus is described as a ubiquitous presence, because antibodies for one (or more)
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 epi ...
s have been found in virtually every mammalian species. This is at least partially due to because the Mammalian orthoreovirus does not rely on
arthropod
Arthropods (, (gen. ποδός)) are invertebrate animals with an exoskeleton, a Segmentation (biology), segmented body, and paired jointed appendages. Arthropods form the phylum Arthropoda. They are distinguished by their jointed limbs and Arth ...
s for transmission as many viruses do. Instead the Mammalian orthoreovirus is transmitted via the
oral-fecal route, meaning in some way an infected host's feces are ingested by another person, or the
aerosol
An aerosol is a suspension (chemistry), suspension of fine solid particles or liquid Drop (liquid), droplets in air or another gas. Aerosols can be natural or Human impact on the environment, anthropogenic. Examples of natural aerosols are fog o ...
route, meaning the viral particles travel through the air and are breathed in by a person.
Entry into cell
Once inside the person the Mammalian orthoreovirus attaches to target cells via the σ1 protein, a filamentous trimer that protrudes from the outer capsid layer. Junctional adhesion molecule-A is a receptor for the Mammalian orthoreovirus regardless of the serotype.
Sialic acid Sialic acids are a class of alpha-keto acid sugars with a nine-carbon backbone.
The term "sialic acid" (from the Greek for saliva, - ''síalon'') was first introduced by Swedish biochemist Gunnar Blix in 1952. The most common member of this gr ...
, resident within the
respiratory system
The respiratory system (also respiratory apparatus, ventilatory system) is a biological system consisting of specific organs and structures used for gas exchange in animals and plants. The anatomy and physiology that make this happen varies grea ...
of most mammals is a co-receptor for Mammalian orthoreovirus Type 3 (Dearing). After binding to the receptors on the surface of the to-be host cell, the virus is brought into the cell via receptor-mediated
endocytosis
Endocytosis is a cellular process in which substances are brought into the cell. The material to be internalized is surrounded by an area of cell membrane, which then buds off inside the cell to form a vesicle containing the ingested material. E ...
. Following the internalization of the virus, the viral outer
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 may ...
is disassembled within the endocytic compartment (the
vesicle
Vesicle may refer to:
; In cellular biology or chemistry
* Vesicle (biology and chemistry), a supramolecular assembly of lipid molecules, like a cell membrane
* Synaptic vesicle
; In human embryology
* Vesicle (embryology), bulge-like features o ...
). This disassembly of the outer
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 may ...
of the virus is performed by endocytic
protease
A protease (also called a peptidase, proteinase, or proteolytic enzyme) is an enzyme that catalyzes (increases reaction rate or "speeds up") proteolysis, breaking down proteins into smaller polypeptides or single amino acids, and spurring the ...
s, during acidic pH conditions. This leads to the removal of the σ3 protein, resulting in the exposure of micro1, a membrane-penetration mediator, as well as a conformational change in the σ1 attachment protein.
Replication and transcription
After the uncoated virus particles penetrate the
endosome
Endosomes are a collection of intracellular sorting organelles in eukaryotic cells. They are parts of endocytic membrane transport pathway originating from the trans Golgi network. Molecules or ligands internalized from the plasma membrane can ...
s, early transcription of the double stranded
RNA
Ribonucleic acid (RNA) is a polymeric molecule essential in various biological roles in coding, decoding, regulation and expression of genes. RNA and deoxyribonucleic acid ( DNA) are nucleic acids. Along with lipids, proteins, and carbohydra ...
genome by viral polymerase occurs inside the uncoated (naked)
viral core
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 may ...
. This process occurs in this manner so the viral
double stranded RNA is not exposed to the
cytoplasm
In cell biology, the cytoplasm is all of the material within a eukaryotic cell, enclosed by the cell membrane, except for the cell nucleus. The material inside the nucleus and contained within the nuclear membrane is termed the nucleoplasm. The ...
, as this would cause the cell to attack the viral particle. The viral core is then released into the
cytoplasm
In cell biology, the cytoplasm is all of the material within a eukaryotic cell, enclosed by the cell membrane, except for the cell nucleus. The material inside the nucleus and contained within the nuclear membrane is termed the nucleoplasm. The ...
of the host cell, where replication occurs. Replication is completed with the aid of protein λ3, which acts as
RNA-dependent RNA polymerase
RNA-dependent RNA polymerase (RdRp) or RNA replicase is an enzyme that catalyzes the replication of RNA from an RNA template. Specifically, it catalyzes synthesis of the RNA strand complementary to a given RNA template. This is in contrast to t ...
. Positive-strand transcripts from each of the
double stranded RNA segments are synthesized, these transcripts are then used as templates for the
translation
Translation is the communication of the Meaning (linguistic), meaning of a #Source and target languages, source-language text by means of an Dynamic and formal equivalence, equivalent #Source and target languages, target-language text. The ...
of proteins, in addition to make the negative-strand
RNA
Ribonucleic acid (RNA) is a polymeric molecule essential in various biological roles in coding, decoding, regulation and expression of genes. RNA and deoxyribonucleic acid ( DNA) are nucleic acids. Along with lipids, proteins, and carbohydra ...
. Viral protein μ2, is a transcriptase cofactor that is a part of
transcription
Transcription refers to the process of converting sounds (voice, music etc.) into letters or musical notes, or producing a copy of something in another medium, including:
Genetics
* Transcription (biology), the copying of DNA into RNA, the fir ...
, it also has enzymatic functions such as capping the
mRNA
In molecular biology, messenger ribonucleic acid (mRNA) is a single-stranded molecule of RNA that corresponds to the genetic sequence of a gene, and is read by a ribosome in the process of Protein biosynthesis, synthesizing a protein.
mRNA is ...
, and acts as
RNA helicase
Helicases are a class of enzymes thought to be vital to all organisms. Their main function is to unpack an organism's genetic material. Helicases are motor proteins that move directionally along a nucleic acid phosphodiester backbone, separating ...
, which separates double stranded
RNA
Ribonucleic acid (RNA) is a polymeric molecule essential in various biological roles in coding, decoding, regulation and expression of genes. RNA and deoxyribonucleic acid ( DNA) are nucleic acids. Along with lipids, proteins, and carbohydra ...
strands.
= Assembly and release
=
Mammalian orthoreovirus messenger RNA transcripts have a short 5’ untranslated region, and do not have 3’ poly A tails, some lack 5’ caps during post-infection. It is unknown as to how uncapped versions of MRV's
mRNA
In molecular biology, messenger ribonucleic acid (mRNA) is a single-stranded molecule of RNA that corresponds to the genetic sequence of a gene, and is read by a ribosome in the process of Protein biosynthesis, synthesizing a protein.
mRNA is ...
are able to use a host cell ribosome in
translation
Translation is the communication of the Meaning (linguistic), meaning of a #Source and target languages, source-language text by means of an Dynamic and formal equivalence, equivalent #Source and target languages, target-language text. The ...
. Mammalian orthoreovirus’ viral proteins and its genomic RNAs aggregate in cytoplasm viral factories. The positive and negative
RNA
Ribonucleic acid (RNA) is a polymeric molecule essential in various biological roles in coding, decoding, regulation and expression of genes. RNA and deoxyribonucleic acid ( DNA) are nucleic acids. Along with lipids, proteins, and carbohydra ...
stands will base pair to create the
double stranded RNA viral genome. The virion is assembled in sub-viral particles in the
cytoplasm
In cell biology, the cytoplasm is all of the material within a eukaryotic cell, enclosed by the cell membrane, except for the cell nucleus. The material inside the nucleus and contained within the nuclear membrane is termed the nucleoplasm. The ...
. Due to the nature of the Mammalian orthoreovirus, its outer (T=13) and inner (T=2) capsid are self-assembled. The
inner capsid proteins require the co-expression of the T2 protein and the σ2 protein, to stabilize the inner capsid structure as well as aid in assembly. The outer capsid's assembly is dependent upon the σ3 viral protein, which aids in the formation of the
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 may ...
. After the virus has been fully assembled and matured, the newly formed Mammalian orthoreovirus particle is released from the host cell, the means in which the virus particle does this is uncertain but it is presumed to happen following
cell death
Cell death is the event of a biological cell ceasing to carry out its functions. This may be the result of the natural process of old cells dying and being replaced by new ones, as in programmed cell death, or may result from factors such as dis ...
and the breakdown of the host
plasma membrane
The cell membrane (also known as the plasma membrane (PM) or cytoplasmic membrane, and historically referred to as the plasmalemma) is a biological membrane that separates and protects the interior of all cells from the outside environment (t ...
.
Interaction with hosts
The Mammalian orthoreovirus as stated previously is ubiquitous among mammals, infecting a large variety of species all over the world. Examples include,
pig
The pig (''Sus domesticus''), often called swine, hog, or domestic pig when distinguishing from other members of the genus '' Sus'', is an omnivorous, domesticated, even-toed, hoofed mammal. It is variously considered a subspecies of ''Sus s ...
s,
cattle
Cattle (''Bos taurus'') are large, domesticated, cloven-hooved, herbivores. They are a prominent modern member of the subfamily Bovinae and the most widespread species of the genus ''Bos''. Adult females are referred to as cows and adult mal ...
,
horse
The horse (''Equus ferus caballus'') is a domesticated, one-toed, hoofed mammal. It belongs to the taxonomic family Equidae and is one of two extant subspecies of ''Equus ferus''. The horse has evolved over the past 45 to 55 million y ...
s,
primate
Primates are a diverse order of mammals. They are divided into the strepsirrhines, which include the lemurs, galagos, and lorisids, and the haplorhines, which include the tarsiers and the simians (monkeys and apes, the latter including huma ...
s,
dog
The dog (''Canis familiaris'' or ''Canis lupus familiaris'') is a domesticated descendant of the wolf. Also called the domestic dog, it is derived from the extinct Pleistocene wolf, and the modern wolf is the dog's nearest living relative. Do ...
s,
cat
The cat (''Felis catus'') is a domestic species of small carnivorous mammal. It is the only domesticated species in the family Felidae and is commonly referred to as the domestic cat or house cat to distinguish it from the wild members of ...
s,
rabbit
Rabbits, also known as bunnies or bunny rabbits, are small mammals in the family Leporidae (which also contains the hares) of the order Lagomorpha (which also contains the pikas). ''Oryctolagus cuniculus'' includes the European rabbit speci ...
s,
mice
A mouse ( : mice) is a small rodent. Characteristically, mice are known to have a pointed snout, small rounded ears, a body-length scaly tail, and a high breeding rate. The best known mouse species is the common house mouse (''Mus musculus' ...
,
marsupial
Marsupials are any members of the mammalian infraclass Marsupialia. All extant marsupials are endemic to Australasia, Wallacea and the Americas. A distinctive characteristic common to most of these species is that the young are carried in a po ...
s, and
human
Humans (''Homo sapiens'') are the most abundant and widespread species of primate, characterized by bipedalism and exceptional cognitive skills due to a large and complex brain. This has enabled the development of advanced tools, culture, ...
s. Experimental infection of Mammalian orthoreovirus Type 3 resulted in 100% mortality in neonatal pigs, the pigs developed
acute gastroenteritis
Gastroenteritis, also known as infectious diarrhea and gastro, is an inflammation of the gastrointestinal tract including the stomach and intestine. Symptoms may include diarrhea, vomiting, and abdominal pain. Fever, lack of energy, and dehydrat ...
and severe
diarrhea
Diarrhea, also spelled diarrhoea, is the condition of having at least three loose, liquid, or watery bowel movements each day. It often lasts for a few days and can result in dehydration due to fluid loss. Signs of dehydration often begin wi ...
within 72 hours of infection. Additionally, it has been reported that MRV-3 causes
enteritis
Enteritis is inflammation of the small intestine. It is most commonly caused by food or drink contaminated with pathogenic microbes,Dugdale, David C., IIII, and George F Longretc"Enteritis" MedlinePlus Medical Encyclopedia, 18 October 2008. Access ...
,
pneumonia
Pneumonia is an inflammatory condition of the lung primarily affecting the small air sacs known as alveoli. Symptoms typically include some combination of productive or dry cough, chest pain, fever, and difficulty breathing. The severity ...
,
encephalitis
Encephalitis is inflammation of the brain. The severity can be variable with symptoms including reduction or alteration in consciousness, headache, fever, confusion, a stiff neck, and vomiting. Complications may include seizures, hallucinations, ...
and reproductive failure in swine. Experimental infection of Mammalian orthoreovirus Type 1 resulted in
pneumonia
Pneumonia is an inflammatory condition of the lung primarily affecting the small air sacs known as alveoli. Symptoms typically include some combination of productive or dry cough, chest pain, fever, and difficulty breathing. The severity ...
,
enteritis
Enteritis is inflammation of the small intestine. It is most commonly caused by food or drink contaminated with pathogenic microbes,Dugdale, David C., IIII, and George F Longretc"Enteritis" MedlinePlus Medical Encyclopedia, 18 October 2008. Access ...
,
fever
Fever, also referred to as pyrexia, is defined as having a body temperature, temperature above the human body temperature, normal range due to an increase in the body's temperature Human body temperature#Fever, set point. There is not a single ...
, and
diarrhea
Diarrhea, also spelled diarrhoea, is the condition of having at least three loose, liquid, or watery bowel movements each day. It often lasts for a few days and can result in dehydration due to fluid loss. Signs of dehydration often begin wi ...
.
References
{{Taxonbar, from=Q18976220
Orthoreoviruses