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Rhabdoviridae | |
---|---|
Vesicular stomatitis Indiana virus (VSV), the prototypical rhabdovirus | |
Virus classification | |
(unranked): | Virus |
Realm: | Riboviria |
Kingdom: | Orthornavirae |
Phylum: | Negarnaviricota |
Class: | Monjiviricetes |
Order: | Mononegavirales |
Family: | Rhabdoviridae |
Genera | |
Rhabdoviridae is a family of negative-strand RNA viruses in the order Mononegavirales . [1] Vertebrates (including mammals and humans), invertebrates, plants, fungi and protozoans serve as natural hosts. [2] [3] [4] Diseases associated with member viruses include rabies encephalitis caused by the rabies virus, and flu-like symptoms in humans caused by vesiculoviruses. The name is derived from Ancient Greek rhabdos, meaning rod, referring to the shape of the viral particles. [5] The family has 40 genera, most assigned to three subfamilies. [6]
The individual virus particles (virions) of rhabdoviruses are composed of RNA, protein, carbohydrate and lipid. They have complex bacilliform or bullet-like shapes. All these viruses have structural similarities and have been classified as a single family. [7]
The virions are about 75 nm wide and 180 nm long. [2] Rhabdoviruses are enveloped and have helical nucleocapsids and their genomes are linear, around 11–15 kb in length. [5] [2] Rhabdoviruses carry their genetic material in the form of negative-sense single-stranded RNA. They typically carry genes for five proteins: large protein (L), glycoprotein (G), nucleoprotein (N), phosphoprotein (P), and matrix protein (M). [8] The sequence of these protein genes from the 3 'end to the 5' end in the genome is N–P–M–G–L. [9] Every rhabdoviruses encode these five proteins in their genomes. In addition to these proteins, many rhabdoviruses encode one or more proteins. [10] The first four genes encode major structural proteins that participate in the structure of the virion envelope. [9]
The matrix protein (M) constitutes a layer between the virion envelope and the nucleocapsid core of the rhabdovirus. [10] In addition to the functions about virus assembly, morphogenesis and budding off enveloped from the host plasma membrane, additional functions such as the regulation of RNA synthesis, affecting the balance of replication and transcription products was found, making reverse genetics experiments with rabies virus, a member of the family Rhabdoviridae. [11] The large (L) protein has several enzymatic functions in viral RNA synthesis and processing. [8] The L gene encodes this L protein, which contains multiple domains. In addition to RNA synthesis, it is thought to be involved in methyl capping and polyadenylation activity. [9]
P protein plays important and multiple roles during transcription and replication of the RNA genome. The multifunctional P protein is encoded by the P gene. P protein acts as a non-catalytic cofactor of large protein polymerase. It is binding to N and L protein. P protein has two independent binding regions. By forming N-P complexes, it can keep the N protein in the form suitable for specific encapsulation. P protein interferes with the host's innate immune system through inhibition of the activities of interferon regulatory factor 3 (IRF3) and signal transducer and activator of transcription 1 (STAT1), thus eliminating the cellular type 1 interferon pathway. Also, P protein acts as an antagonist against antiviral PML function. [12] [13]
Rhabdoviruses that infect vertebrates (especially mammals and fishes), plants, and insects are usually bullet-shaped. [14] However, in contrast to paramyxoviruses, rhabdoviruses do not have hemagglutinating and neuraminidase activities. [14]
Transcriptase of rhabdovirus is composed of 1 L and 3 P proteins. Transcriptase components are always present in the complete virion to permit rhabdoviruses to begin transcription immediately after entry.[ citation needed ]
The rhabdovirus transcriptase proceeds in a 3' to 5' direction on the genome and the transcription terminates randomly at the end of protein sequences. For example, if a transcription finishes at the end of M sequence; leader RNA and N, P and M mRNAs are formed separately from each other.[ citation needed ]
Also, mRNAs accumulate according to the order of protein sequences on the genome, solving the logistics problem in the cell. For example, N protein is necessary in high quantities for the virus, as it coats the outside of the replicated genomes completely. Since the N protein sequence is located at the beginning of the genome (3' end) after the leader RNA sequence, mRNAs for N protein can always be produced and accumulate in high amounts with every termination of transcription. After the transcription processes, all of the mRNAs are capped at the 5' end and polyadenylated at the 3' end by L protein.
This transcription mechanism thus provides mRNAs according to the need of the viruses. [10] : 173–184
The virus proteins translated on free ribosomes but G protein is translated by the rough endoplasmic reticulum. This means G protein has a signal peptide on its mRNA's starting codes. Phosphoproteins (P) and glycoprotein (G) undergo post-translational modification. Trimers of P protein are formed after phosphorylation by kinase activity of L protein. The G protein is glycosylated in the rough endoplasmic reticulum and the Golgi complex. [10] : 180
Viral replication is cytoplasmic. The replication cycle is the same for most rhabdoviruses. All components required for early transcription and the nucleocapsid are released to the cytoplasm of the infected cell after the first steps of binding, penetration and uncoating take place. [9] Entry into the host cell is achieved by attachment of the viral G glycoproteins to host receptors, which mediates clathrin-mediated endocytosis. Replication follows the negative stranded RNA virus replication model. Negative stranded RNA virus transcription, using polymerase stuttering is the method of transcription. The virus exits the host cell by budding, and tubule-guided viral movement. Transmission routes are zoonosis and bite. [5] [2]
Replication of many rhabdoviruses occurs in the cytoplasm, although several of the plant infecting viruses replicate in the nucleus. [15] The rhabdovirus matrix (M) protein is very small (~20–25 kDa) however plays a number of important roles during the replication cycle of the virus. These proteins of rhabdoviruses constitute major structural components of the virus and they are multifunctional proteins and required for virus maturation and viral budding process that also regulate the balance of virus RNA synthesis by shifting synthesis from transcription to replication. [16] In order for replication, both the L and P protein must be expressed to regulate transcription. [17] Phosphoprotein (P) also plays a crucial role during replication, as N-P complexes, rather than N alone, are necessary for appropriate and selective encapsidation of viral RNA. Therefore, replication is not possible after infection until the primary transcription and translation produce enough N protein. [18]
The L protein has a lot of enzymatic activity such as RNA replication, capping mRNAs phosphorylation of P. L protein gives feature in about replication in cytoplasm. [17] Transcription results in five monocistronic mRNAs being produced because the intergenic sequences act as both termination and promoter sequences for adjacent genes. This type of transcription mechanism is explained by stop-start model (stuttering transcription). Owing to stop-start model, the large amounts of the structural proteins are produced. According to this model, the virus-associated RNA polymerase starts firstly the synthesis of leader RNA and then the five mRNA which will produce N, P, M, G, L proteins, respectively. After the leader RNA was produced, the polymerase enzyme reinitiates virion transcription on N gene and proceeds its synthesis until it ends 3′ end of the chain. Then, the synthesis of P mRNAs are made by same enzyme with new starter sinyal. These steps continue until the enzyme arrives the end of the L gene. During transcription process, the polymerase enzyme may leave the template at any point and then bound just at the 3′ end of the genome RNA to start mRNA synthesis again. This process will results concentration gradient of the amount of mRNA based on its place and its range from the 3′ end. In the circumstances, the amounts of mRNA species change and will be produced N>P>M>G>L proteins. [19] During their synthesis the mRNAs are processed to introduce a 5' cap and a 3’ polyadenylated tail to each of the molecules. This structure is homologous to cellular mRNAs and can thus be translated by cellular ribosomes to produce both structural and non-structural proteins.
Genomic replication requires a source of newly synthesized N protein to encapsidate the RNA. This occurs during its synthesis and results in the production of a full-length anti-genomic copy. This in turn is used to produce more negative-sense genomic RNA. The viral polymerase is required for this process, but how the polymerase engages in both mRNA synthesis and genomic replication is not well understood.
Replication characteristically occurs in an inclusion body within the cytoplasm, from where they bud through various cytoplasmic membranes and the outer membrane of the cell. This process results in the acquisition of the M + G proteins, responsible for the characteristic bullet- shaped morphology of the virus.
These viruses fall into four groups based on the RNA polymerase gene. [20] The basal clade appears to be novirhabdoviruses, which infect fish. Cytorhabdoviruses and the nucleorhabdoviruses, which infect plants, are sister clades. Lyssaviruses form a clade of their own which is more closely related to the land vertebrate and insect clades than to the plant viruses. The remaining viruses form a number of highly branched clades and infect arthropods and land vertebrates.
A 2015 analysis of 99 species of animal rhabdoviruses found that they fell into 17 taxonomic groupings, eight – Lyssavirus, Vesiculovirus, Perhabdovirus, Sigmavirus, Ephemerovirus, Tibrovirus, Tupavirus and Sprivivirus – which were previously recognized. [21] The authors proposed seven new taxa on the basis of their findings: "Almendravirus", "Bahiavirus", "Curiovirus", "Hapavirus", "Ledantevirus", "Sawgravirus" and "Sripuvirus". Seven species did not group with the others suggesting the need for additional taxa.
An unofficial supergroup – "Dimarhabdovirus" – refers to the genera Ephemerovirus and Vesiculovirus. [22] A number of other viruses that have not been classified into genera also belong to this taxon. This supergroup contains the genera with species that replicate in both vertebrate and invertebrate hosts and have biological cycles that involve transmission by haematophagous dipterans (bloodsucking flies).
The prototypical and best studied rhabdovirus is vesicular stomatitis Indiana virus. It is a preferred model system to study the biology of rhabdoviruses, and mononegaviruses in general. The mammalian disease rabies is caused by lyssaviruses, of which several have been identified.
Rhabdoviruses are important pathogens of animals and plants. Rhabdoviruses are transmitted to hosts by arthropods, such as aphids, planthoppers, leafhoppers, black flies, sandflies, and mosquitoes.
In September 2012, researchers writing in the journal PLOS Pathogens described a novel species of rhabdovirus, called Bas-Congo virus (BASV), which was discovered in a blood sample from a patient who survived an illness that resembled hemorrhagic fever. [20] No cases of BASV have been reported since its discovery and it is uncertain if BASV was the actual cause of the patient's illness. [23]
In 2015 two novel rhabdoviruses, Ekpoma virus 1 and Ekpoma virus 2, were discovered in samples of blood from two healthy women in southwestern Nigeria. Ekpoma virus 1 and Ekpoma virus 2 appear to replicate well in humans (viral load ranged from ~45,000 - ~4.5 million RNA copies/mL plasma) but did not cause any observable symptoms of disease. [24] Exposure to Ekpoma virus 2 appears to be widespread in certain parts of Nigeria where seroprevalence rates are close to 50%. [24]
In the Alpharhabdovirinae subfamily, the following genera are recognized: [6]
The genera of the other subfamilies are as follows: [6]
The following genera are unassigned to the a subfamily: [6]
In addition to the above, there are a large number of rhabdo-like viruses that have not yet been officially classified by the ICTV. [5]
An RNA virus is a virus—other than a retrovirus—that has ribonucleic acid (RNA) as its genetic material. The nucleic acid is usually single-stranded RNA (ssRNA) but it may be double-stranded (dsRNA). Notable human diseases caused by RNA viruses include the common cold, influenza, SARS, MERS, COVID-19, Dengue virus, hepatitis C, hepatitis E, West Nile fever, Ebola virus disease, rabies, polio, mumps, and measles.
Paramyxoviridae is a family of negative-strand RNA viruses in the order Mononegavirales. Vertebrates serve as natural hosts. Diseases associated with this family include measles, mumps, and respiratory tract infections. The family has four subfamilies, 17 genera, three of which are unassigned to a subfamily, and 78 species.
Henipavirus is a genus of negative-strand RNA viruses in the family Paramyxoviridae, order Mononegavirales containing six established species, and numerous others still under study. Henipaviruses are naturally harboured by several species of small mammals, notably pteropid fruit bats, microbats of several species, and shrews. Henipaviruses are characterised by long genomes and a wide host range. Their recent emergence as zoonotic pathogens capable of causing illness and death in domestic animals and humans is a cause of concern.
Mononegavirales is an order of negative-strand RNA viruses which have nonsegmented genomes. Some members that cause human disease in this order include Ebola virus, human respiratory syncytial virus, measles virus, mumps virus, Nipah virus, and rabies virus. Important pathogens of nonhuman animals and plants are also in the group. The order includes eleven virus families: Artoviridae, Bornaviridae, Filoviridae, Lispiviridae, Mymonaviridae, Nyamiviridae, Paramyxoviridae, Pneumoviridae, Rhabdoviridae, Sunviridae, and Xinmoviridae.
Hepadnaviridae is a family of viruses. Humans, apes, and birds serve as natural hosts. There are currently 18 species in this family, divided among 5 genera. Its best-known member is hepatitis B virus. Diseases associated with this family include: liver infections, such as hepatitis, hepatocellular carcinomas, and cirrhosis. It is the sole accepted family in the order Blubervirales.
Lyssavirus is a genus of RNA viruses in the family Rhabdoviridae, order Mononegavirales. Mammals, including humans, can serve as natural hosts. The genus Lyssavirus includes the rabies virus traditionally associated with the disease of the same name.
Rabies virus, scientific name Rabies lyssavirus, is a neurotropic virus that causes rabies in animals, including humans. Rabies transmission can occur through the saliva of animals and less commonly through contact with human saliva. Rabies lyssavirus, like many rhabdoviruses, has an extremely wide host range. In the wild it has been found infecting many mammalian species, while in the laboratory it has been found that birds can be infected, as well as cell cultures from mammals, birds, reptiles and insects. Rabies is reported in more than 150 countries and on all continents except Antarctica. The main burden of disease is reported in Asia and Africa, but some cases have been reported also in Europe in the past 10 years, especially in returning travellers.
Birnaviridae is a family of double-stranded RNA viruses. Salmonid fish, birds and insects serve as natural hosts. There are currently 11 species in this family, divided among seven genera. Diseases associated with this family include infectious pancreatic necrosis in salmonid fish, which causes significant losses to the aquaculture industry, with chronic infection in adult salmonid fish and acute viral disease in young salmonid fish.
Tombusviridae is a family of single-stranded positive sense RNA plant viruses. There are three subfamilies, 17 genera, and 95 species in this family. The name is derived from Tomato bushy stunt virus (TBSV).
Viral replication is the formation of biological viruses during the infection process in the target host cells. Viruses must first get into the cell before viral replication can occur. Through the generation of abundant copies of its genome and packaging these copies, the virus continues infecting new hosts. Replication between viruses is greatly varied and depends on the type of genes involved in them. Most DNA viruses assemble in the nucleus while most RNA viruses develop solely in cytoplasm.
Chandipura vesiculovirus (CHPV) is a member of the Rhabdoviridae family that is associated with an encephalitic illness in humans. It was first identified in 1965 after isolation from the blood of two patients from Chandipura village in Maharashtra state, India and has been associated with a number of otherwise unexplained outbreaks of encephalitic illness in central India. The most recent occurred in Andhra Pradesh and Maharashtra in June–August 2003 with 329 children affected and 183 deaths. Further sporadic cases and deaths in children were observed in Gujarat state in 2004.
Infectious hematopoietic necrosis virus (IHNV), is a negative-sense single-stranded, bullet-shaped RNA virus that is a member of the Rhabdoviridae family, and from the genus Novirhabdovirus. It causes the disease known as infectious hematopoietic necrosis in salmonid fish such as trout and salmon. The disease may be referred to by a number of other names such as Chinook salmon disease, Coleman disease, Columbia River sockeye disease, Cultus Lake virus disease, Oregon sockeye disease, Sacramento River Chinook disease and sockeye salmon viral disease. IHNV is commonly found in the Pacific Coast of Canada and the United States, and has also been found in Europe and Japan. The first reported epidemics of IHNV occurred in the United States at the Washington and the Oregon fish hatcheries during the 1950s. IHNV is transmitted following shedding of the virus in the feces, urine, sexual fluids, and external mucus and by direct contact or close contact with the surrounding water. The virus gains entry into fish at the base of the fins.
Novirhabdovirus is a genus of the family Rhabdoviridae containing viruses known to infect aquatic hosts. They can be transmitted from fish to fish or by waterborne virus, as well as through contaminated eggs. Replication and thermal inactivation temperatures are generally lower than for other rhabdoviruses, given the cold-blooded nature of their hosts. Hosts include a large and growing range of marine and freshwater fish.
Snakehead rhabdovirus (SHRV) is a novirhabdovirus that affects warm water wild and pond-cultured fish of various species in Southeast Asia, including snakehead for which it is named.
Ephemerovirus is a genus of viruses in the family Rhabdoviridae, order Mononegavirales. Cattle and mosquitoes serve as natural hosts. Diseases associated with viruses in this genus include: sudden fever.
Tibrovirus is a poorly characterized genus of viruses in the family Rhabdoviridae, order Mononegavirales. There are 8 members of the genus. Tibroviruses have been isolated from biting midges, cattle, and humans. None of the tibroviruses, except for Bas-Congo virus, have been associated with any diseases.
Pneumoviridae is a family of negative-strand RNA viruses in the order Mononegavirales. Humans, cattle, and rodents serve as natural hosts. Respiratory tract infections are associated with member viruses such as human respiratory syncytial virus. There are five species in the family which are divided between the genera Metapneumovirus and Orthopneumovirus. The family used to be considered as a sub-family of Paramyxoviridae, but has been reclassified as of 2016.
Avian metaavulavirus 2, formerly Avian paramyxovirus 2, is a species of virus belonging to the family Paramyxoviridae and genus Metaavulavirus. The virus is a negative strand RNA virus containing a monopartite genome. Avian metaavulavirus 2 is one of nine species belonging to the genus Metaavulavirus. The most common serotype of Avulavirinae is serotype 1, the cause of Newcastle disease (ND). Avian metaavulavirus 2 has been known to cause disease, specifically mild respiratory infections in domestic poultry, including turkeys and chickens, and has many economic effects on egg production and poultry industries. The virus was first isolated from a strain in Yucaipa, California in 1956. Since then, other isolates of the virus have been isolated worldwide.
Negative-strand RNA viruses are a group of related viruses that have negative-sense, single-stranded genomes made of ribonucleic acid (RNA). They have genomes that act as complementary strands from which messenger RNA (mRNA) is synthesized by the viral enzyme RNA-dependent RNA polymerase (RdRp). During replication of the viral genome, RdRp synthesizes a positive-sense antigenome that it uses as a template to create genomic negative-sense RNA. Negative-strand RNA viruses also share a number of other characteristics: most contain a viral envelope that surrounds the capsid, which encases the viral genome, −ssRNA virus genomes are usually linear, and it is common for their genome to be segmented.
West Caucasian bat lyssavirus (WCBL) is a member of genus Lyssavirus, family Rhabdoviridae and order Mononegavirales. This virus was first isolated from Miniopterus schreibersii, in the western Caucasus Mountains of southeastern Europe in 2002. WCBL is the most divergent form of Lyssavirus, and is found in Miniopterus bats (insectivorous), Rousettus aegyptiacus, and Eidolon helvum. The latter two are both fruit bats. The virus is fragile as it can be inactivated by UV light and chemicals, such as ether, chloroform, and bleach. WCBL has not been known to infect humans thus far.