''Mesoniviridae'' is a family of enveloped,

positive-strand RNA viruses Positive-strand RNA viruses (+ssRNA viruses) are a group of related viruses that have positive-sense, single-stranded genomes made of ribonucleic acid. The positive-sense genome can act as messenger RNA (mRNA) and can be directly translated in ...

in the order ''

Nidovirales ''Nidovirales'' is an order of enveloped, positive-strand RNA viruses which infect vertebrates and invertebrates. Host organisms include mammals, birds, reptiles, amphibians, fish, arthropods, molluscs, and helminths. The order includes the fami ...

'' which infect

mosquitoes Mosquitoes (or mosquitos) are members of a group of almost 3,600 species of small flies within the family Culicidae (from the Latin ''culex'' meaning "gnat"). The word "mosquito" (formed by ''mosca'' and diminutive ''-ito'') is Spanish for "litt ...

. The family is named after the size of the genomes relative to other nidoviruses, with ''meso-'' coming from the

Greek Greek may refer to: Greece Anything of, from, or related to Greece, a country in Southern Europe: *Greeks, an ethnic group. *Greek language, a branch of the Indo-European language family. **Proto-Greek language, the assumed last common ancestor ...

word ''mesos'', which means medium, and -''ni'' being an abbreviation of ''nido''.

History

The family is relatively new, having only been discovered in 2011. The first virus, which was named ''Nam Dinh virus'', was found in the Vietnamese province of

Nam Định Nam Định () is a city in the Red River Delta of northern Vietnam. It is the capital of Nam Định Province. The city of Nam Định is 90 km south-east of Vietnam's capital, Hanoi. From August 18–20 of each year, there is a festival hel ...

. The second virus, named ''Cavally virus'', was then found in

Côte d'Ivoire Ivory Coast, also known as Côte d'Ivoire, officially the Republic of Côte d'Ivoire, is a country on the southern coast of West Africa. Its capital is Yamoussoukro, in the centre of the country, while its largest city and economic centre is ...

. These two viruses were later found to be of the same species. A third member of this first species, named ''Dak Nong virus'', was later found in ''

Culex tritaeniorhynchus ''Culex (Culex) tritaeniorhynchus'' is a species of mosquito and is the main vector of the disease Japanese encephalitis. This mosquito is a native of northern Asia, and parts of Africa (northeast and sub-Saharan). Females target large animals f ...

'' populations in Vietnam. In 2013, four more mesoniviruses were discovered in mosquito populations, all within Côte d'Ivoire, and in 2014 four mesoniviruses were discovered in mosquito populations in Australia, Indonesia, and Thailand.

Virology

Structure

Members of this family are enveloped, spherical in shape and 60–80 nm in diameter with club-shaped surface spikes. There are eight major structural proteins, including a nucleocapsid protein (25 kDa in weight), four differentially glycosylated forms of the membrane protein (20, 19, 18 and 17 kDa) and the spike (S) protein (77 kDa), which is cleaved to produce two S protein subunits (23 and 57 kDa).

Genome

The genomes are linear, positive-sense,

polycistronic A cistron is an alternative term for "gene". The word cistron is used to emphasize that genes exhibit a specific behavior in a cis-trans test; distinct positions (or loci) within a genome are cistronic. History The words ''cistron'' and ''gene ...

, single-stranded RNA, and are about 20,000 nucleotides in length, with a 3'

poly(A) tail Polyadenylation is the addition of a poly(A) tail to an RNA transcript, typically a messenger RNA (mRNA). The poly(A) tail consists of multiple adenosine monophosphates; in other words, it is a stretch of RNA that has only adenine bases. In euk ...

and seven major

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 readin ...

s (ORFs). Two overlapping ORFs, together known as

ORF1ab ORF1ab (also ORF1a/b) refers collectively to two open reading frames (ORFs), ORF1a and ORF1b, that are conserved in the genomes of nidoviruses, a group of viruses that includes coronaviruses. The genes express large polyproteins that undergo pro ...

, are at the 5'-end, encoding the major non-structural proteins and are expressed as a

fusion protein Fusion proteins or chimeric (kī-ˈmir-ik) proteins (literally, made of parts from different sources) are proteins created through the joining of two or more genes that originally coded for separate proteins. Translation of this ''fusion gene'' r ...

ribosomal frameshift Ribosomal frameshifting, also known as translational frameshifting or translational recoding, is a biological phenomenon that occurs during translation that results in the production of multiple, unique proteins from a single mRNA. The process can ...

. ORFs 1a and 1b contain six

replicase 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 ...

domains, as well as the 3'-5'

exoribonuclease An exoribonuclease is an exonuclease ribonuclease, which are enzymes that degrade RNA by removing terminal nucleotides from either the 5' end or the 3' end of the RNA molecule. Enzymes that remove nucleotides from the 5' end are called ''5'-3' e ...

(ExoN) that controls RNA replication fidelity and a 2'-O-methyltransferase, both of which are found in larger nidoviruses. ORF 1b also encodes an N7-methyltransferase.

Taxonomy

''Mesoniviridae'' is a member of the order ''Nidovirales'', an order of +ssRNA viruses with animal hosts. The family has only one subfamily, ''Hexponivirinae'', which contains only one genus, ''Alphamesonivirus''. There are 8 subgenera and 10 species in ''Alphamesonivirus'': *''

Alphamesonivirus ''Mesoniviridae'' is a family of enveloped, positive-strand RNA viruses in the order ''Nidovirales'' which infect mosquitoes. The family is named after the size of the genomes relative to other nidoviruses, with ''meso-'' coming from the Greek w ...

'' **'' Casualivirus'' ***''

Alphamesonivirus 4 ''Mesoniviridae'' is a family of enveloped, positive-strand RNA viruses in the order ''Nidovirales'' which infect mosquitoes. The family is named after the size of the genomes relative to other nidoviruses, with ''meso-'' coming from the Greek w ...

'' **'' Enselivirus'' ***''

Alphamesonivirus 8 ''Mesoniviridae'' is a family of Viral envelope, enveloped, Positive-strand RNA virus, positive-strand RNA viruses in the order ''Nidovirales'' which infect Mosquito, mosquitoes. The family is named after the size of the genomes relative to other ...

'' **'' Hanalivirus'' ***''

Alphamesonivirus 5 ''Mesoniviridae'' is a family of enveloped, positive-strand RNA viruses in the order ''Nidovirales'' which infect mosquitoes. The family is named after the size of the genomes relative to other nidoviruses, with ''meso-'' coming from the Greek w ...

'' **'' Kadilivirus'' ***''

Alphamesonivirus 7 ''Mesoniviridae'' is a family of enveloped, positive-strand RNA viruses in the order ''Nidovirales'' which infect mosquitoes. The family is named after the size of the genomes relative to other nidoviruses, with ''meso-'' coming from the Greek w ...

'' **'' Karsalivirus'' ***''

Alphamesonivirus 2 ''Mesoniviridae'' is a family of Viral envelope, enveloped, Positive-strand RNA virus, positive-strand RNA viruses in the order ''Nidovirales'' which infect Mosquito, mosquitoes. The family is named after the size of the genomes relative to other ...

'' ***'' Alphamesonivirus 3'' **'' Menolivirus'' ***'' Alphamesonivirus 9'' **'' Namcalivirus'' ***'' Alphamesonivirus 1'' ***''

Alphamesonivirus 10 ''Mesoniviridae'' is a family of enveloped, positive-strand RNA viruses in the order ''Nidovirales'' which infect mosquitoes. The family is named after the size of the genomes relative to other nidoviruses, with ''meso-'' coming from the Greek w ...

'' **'' Ofalivirus'' ***'' Alphamesonivirus 6'' The discovery and phylogenetic analysis of four additional mesoniviruses in 2013, named Hana virus, Méno virus, Nsé virus and Moumo virus, has suggested that they represent at least three new species of mesoniviruses. Additionally, in 2014 four potentially new species were discovered in Australia, Indonesia, and Thailand, named Casuarina virus, Karang Sari virus, Bontag Baru virus, and Kamphaeng Phet virus, respectively.

References

External links

Notes on Family:Mesoniviridae
{{Taxonbar, from=Q15642827, from2=Q57751768, from3=Q18814367 Nidovirales Virus families