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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.〔Receveur MC, Grandadam M, Pistone T, Malvy D. ''Infection with Mayaro virus in a French traveller returning from the Amazon region, Brazil, January'', 2010 . Euro Surveill. 2010;15(18):pii=19563. Available online: http://www.eurosurveillance.org/ViewArticle.aspx?ArticleId=19563.〕 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.〔 ==Virology== Mayaro Virus has a structure similar to other Alphavirus. MAYV 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.〔Lavergne A, de Thoisy B, Lacoste V, Pascalis H, Pouliquen JF, Mercier V, Tolou H, Dussart P, Morvan J, Talarmin A, Kazanji M. “Mayaro virus: complete nucleotide sequence and phylogenetic relationships with other alphaviruses”. 〕〔Mourão MP, Bastos Mde S, de Figueiredo RP, Gimaque JB, Galusso Edos S, Kramer VM, de Oliveira CM, Naveca FG, Figueiredo LT. “Mayaro fever in the city of Manaus, Brazil, 2007-2008”. 〕 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).〔〔Snyder AJ, Mukhopadhyay S. “The alphavirus E3 glycoprotein functions in a clade-specific manner”. 〕〔Firth AE, Chung BY, Fleeton MN, Atkins JF. “Discovery of frameshifting in Alphavirus 6K resolves a 20-year enigma”. 〕〔Muñoz M., Navarro J.C. “Virus Mayaro: un arbovirus reemergente en Venezuela y Latinoamérica”. Biomédica vol.32 no.2 Bogotá Apr./June 2012〕 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.〔Netto M.C.M.G., Shirako Y., Strauss E.G., Carvalho M.G.C., Strauss J.H. Submitted (FEB-2000) to the EMBL/GenBank/DDBJ databases〕〔Leung JY, Ng MM, Chu JJ. “Replication of alphaviruses: a review on the entry process of alphaviruses into cells”. 〕 The envelope lipid component is critical for virus particle stability and infectivity in mammalian cells〔Sousa IP Jr, Carvalho CA, Ferreira DF, Weissmüller G, Rocha GM, Silva JL, Gomes AM. “Envelope lipid-packing as a critical factor for the biological activity and stability of alphavirus particles isolated from mammalian and mosquito 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.〔 The MAYV sequences analysis showed two genotypes (D and L). The amplicon used for phylogenetic analysis includes E1 and E2 glycoprotein genes and the 3’ NCR. The genotype D is distributed in Trinidad, Brasil, French Guiana, Surinam, Peru and Bolivia while the genotype L is limited to the northcentral region of Brasil〔Powers A, Aguilar P, Chandler L, Brault A, Meakins T, Watts D, et al. Genetic relationships among Mayaro and Una viruses suggest distinct patterns of transmission. 〕 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Mayaro virus disease」の詳細全文を読む スポンサード リンク
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