Mayaro virus
| Mayaro virus | |
|---|---|
| Virus classification | |
| Group: | Group IV ((+)ssRNA) |
| Order: | Unassigned |
| Family: | Togaviridae |
| Genus: | Alphavirus |
| Species: | Mayaro virus |
Mayaro virus disease is a mosquitoborne zoonotic pathogen endemic to certain humid forests of tropical South America. Infection with Mayaro virus causes an acute, self-limited dengue-like illness of 3–5 days' duration. The causative virus, abbreviated MAYV, is in the family Togaviridae, and genus Alphavirus. It is closely related to other alphaviruses that produce a dengue-like illness accompanied by long-lasting arthralgia. It is only known to circulate in tropical South America.
Mayaro Virus has a structure similar to other Alphavirus. It is an enveloped virus and has an icosahedral capsid with a diameter of 70 nm. The virus genome is composed of a linear, positive sense, single-stranded RNA with 11,429 nucleotides, excluding the 5’ cap nucleotide and 3’ poly(A) tail.
The MAYV RNA genome contains the 5’ untranslated region (UTR), 3’ non-coding region (NCR) and two open reading frames (ORFs). The 5’ proximal and 3’ proximal ORFs are separated by a short non-coding sequence and represent two-third and one-third of the genomic RNA, respectively. The 5’-proximal ORF codes for a polyprotein that after cleavage forms non-structural proteins (nsP1, nsP2, nsP3, nsP4) and the 3’-proximal ORF with a 26S promoter codes for a polyprotein that is cleaved into structural proteins to generate capsid proteins and envelope surface glycoproteins (E1, E2, E3, C, 6K).
The non-structural proteins (nsP) play different functions in the virus cycle. The non-structural protein 1 (nsP1) is an mRNA-capping enzyme, nsP2 has protease activity, nsP4 is a RNA-direct RNA polymerase. The structural polyprotein is cleaved into 6 chains: Capsid protein (C), p62, E3 protein or spike glycoprotein E3, E2 envelope glycoprotein or spike glycoprotein E2, 6K protein, E1 envelope glycoprotein known also as spike glycoprotein E1. The envelope lipid component is critical for virus particle stability and infectivity in mammalian cells Once the virus enters into the host cell, the genomic RNA is released into the cytoplasm, where the two ORFs are translated into proteins and the synthesis of negative-strand RNA starts. A consecutive synthesis of positive-strand RNA takes place.
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