RESUMO
Chikungunya virus (CHIKV), a mosquito-borne alphavirus of increasing public health significance, has caused large epidemics in Africa and the Indian Ocean basin; now it is spreading throughout the Americas. The primary vectors of CHIKV are Aedes (Ae.) aegypti and, after the introduction of a mutation in the E1 envelope protein gene, the highly anthropophilic and geographically widespread Ae. albopictus mosquito. We review here research efforts to characterize the viral genetic basis of mosquito-vector interactions, the use of RNA interference and other strategies for the control of CHIKV in mosquitoes, and the potentiation of CHIKV infection by mosquito saliva. Over the past decade, CHIKV has emerged on a truly global scale. Since 2013, CHIKV transmission has been reported throughout the Caribbean region, in North America, and in Central and South American countries, including Brazil, Columbia, Costa Rica, El Salvador, French Guiana, Guatemala, Guyana, Nicaragua, Panama, Suriname, and Venezuela. Closing the gaps in our knowledge of driving factors behind the rapid geographic expansion of CHIKV should be considered a research priority. The abundance of multiple primate species in many of these countries, together with species of mosquito that have never been exposed to CHIKV, may provide opportunities for this highly adaptable virus to establish sylvatic cycles that to date have not been seen outside of Africa. The short-term and long-term ecological consequences of such transmission cycles, including the impact on wildlife and people living in these areas, are completely unknown.
Assuntos
Aedes/virologia , Febre de Chikungunya/transmissão , Vírus Chikungunya/genética , Insetos Vetores/virologia , Controle de Mosquitos , Animais , América Central/epidemiologia , Febre de Chikungunya/virologia , Vírus Chikungunya/fisiologia , Geografia , Humanos , América do Norte/epidemiologia , Interferência de RNA , América do Sul/epidemiologiaRESUMO
St. Louis encephalitis virus (SLEV) has been regularly isolated throughout the Americas since 1933. Previous phylogenetic studies involving 62 isolates have defined seven major lineages (I-VII), further divided into 14 clades. In this study, 28 strains isolated in Texas in 1991 and 2001-2003, and three older, previously unsequenced strains from Jamaica and California were sequenced over the envelope protein gene. The inclusion of these new sequences, and others published since 2001, has allowed better delineation of the previously published SLEV lineages, in particular the clades of lineage II. Phylogenetic analysis of 106 isolates identified 13 clades. All 1991 and 2001-2003 isolates from Nueces, Jefferson and Harris Counties (Texas Gulf Coast) group in clade IIB with other isolates from these counties isolated during the 1980s and 1990s. This lack of evidence for introduction of novel strains into the Texas Gulf Coast over a long period of time is consistent with overwintering of SLEV in this region. Two El Paso isolates, both from 2002, group in clade VA with recent Californian isolates from 1998-2001 and some South American strains with a broad temporal range. Overall, these data are consistent with multiple introductions of SLEV from South America into North America, and provide support for the hypothesis that in most situations, SLEV circulates within a locality, with occasional incursions from other areas. Finally, SLEV has much lower nucleotide (10.1 %) and amino acid variation (2.8 %) than other members of the Japanese encephalitis virus complex (maximum variation 24.6 % nucleotide and 11.8 % amino acid).
Assuntos
Vírus da Encefalite de St. Louis/classificação , Vírus da Encefalite de St. Louis/genética , Encefalite de St. Louis/epidemiologia , Variação Genética , Proteínas do Envelope Viral/genética , California/epidemiologia , Vírus da Encefalite de St. Louis/isolamento & purificação , Encefalite de St. Louis/virologia , Humanos , Jamaica/epidemiologia , Modelos Moleculares , Filogenia , Análise de Sequência de DNA , Texas/epidemiologiaRESUMO
Yellow fever virus (YFV) is the prototype member of the genus Flavivirus, a group of viruses that are transmitted between vertebrates by arthropod vectors. The virus is found in tropical regions of Africa and South America and is transmitted to primates by mosquitoes: Aedes spp. in Africa and Haemagogus and Sabethes spp. in South America. Despite the availability of an effective vaccine, yellow fever (YF) is considered a reemerging disease owing to its increased incidence in the past 25 years. Molecular epidemiologic data suggest there are seven genotypes of YFV that are geographically separated, and outbreaks of disease are more associated with particular genotypes. In addition, the risk of urban YF, owing to transmission of the virus by Aedes aegypti, is increasing in Africa, as is the potential of urban YF returning to South America. Both present serious potential public health problems to large population centers.
Assuntos
Aedes/virologia , Febre Amarela/transmissão , Vírus da Febre Amarela , Aedes/fisiologia , África , Animais , Humanos , Controle de Mosquitos , Risco , América do Sul , Viagem , População Urbana , Febre Amarela/epidemiologia , Febre Amarela/prevenção & controle , Vacina contra Febre Amarela/provisão & distribuição , Vírus da Febre Amarela/genéticaRESUMO
The 3' noncoding region (3' NCR) of flaviviruses contains secondary and tertiary structures essential for virus replication. Previous studies of yellow fever virus (YFV) and dengue virus have found that modifications to the 3' NCR are sometimes associated with attenuation in vertebrate and/or mosquito hosts. The 3' NCRs of 117 isolates of South American YFV have been examined, and major deletions and/or duplications of conserved RNA structures have been identified in several wild-type isolates. Nineteen isolates (designated YF-XL isolates) from Brazil, Trinidad, and Venezuela, dating from 1973 to 2001, exhibited a 216-nucleotide (nt) duplication, yielding a tandem repeat of conserved hairpin, stem-loop, dumbbell, and pseudoknot structures. YF-XL isolates were found exclusively within one subclade of South American genotype I YFV. One Brazilian isolate exhibited, in addition to the 216-nt duplication, a deletion of a 40-nt repeated hairpin (RYF) motif (YF-XL-DeltaRYF). To investigate the biological significance of these 3' NCR rearrangements, YF-XL-DeltaRYF and YF-XL isolates, as well as other South American YFV isolates, were evaluated for three phenotypes: growth kinetics in cell culture, neuroinvasiveness in suckling mice, and ability to replicate and produce disseminated infections in Aedes aegypti mosquitoes. YF-XL-DeltaRYF and YF-XL isolates showed growth kinetics and neuroinvasive characteristics comparable to those of typical South American YFV isolates, and mosquito infectivity trials demonstrated that both types of 3' NCR variants were capable of replication and dissemination in a laboratory-adapted colony of A. aegypti.
Assuntos
Camundongos , Animais , Humanos , Research Support, Non-U.S. Gov't , Research Support, U.S. Gov't, P.H.S. , Aedes/virologia , Sequência de Bases , Células Cultivadas , Variação Genética , Dados de Sequência Molecular , Conformação de Ácido Nucleico , Filogenia , RNA não Traduzido/química , RNA não Traduzido/genética , RNA não Traduzido/fisiologia , RNA Viral/química , RNA Viral/genética , RNA Viral/fisiologia , Vírus da Febre Amarela/classificação , Vírus da Febre Amarela/crescimento & desenvolvimento , Vírus da Febre Amarela/genética , Vírus da Febre Amarela/isolamento & purificação , Vírus da Febre Amarela/patogenicidade , Trinidad e Tobago , Brasil , VenezuelaRESUMO
The 3' noncoding region (3' NCR) of flaviviruses contains secondary and tertiary structures essential for virus replication. Previous studies of yellow fever virus (YFV) and dengue virus have found that modifications to the 3' NCR are sometimes associated with attenuation in vertebrate and/or mosquito hosts. The 3' NCRs of 117 isolates of South American YFV have been examined, and major deletions and/or duplications of conserved RNA structures have been identified in several wild-type isolates. Nineteen isolates (designated YF-XL isolates) from Brazil, Trinidad, and Venezuela, dating from 1973 to 2001, exhibited a 216-nucleotide (nt) duplication, yielding a tandem repeat of conserved hairpin, stem-loop, dumbbell, and pseudoknot structures. YF-XL isolates were found exclusively within one subclade of South American genotype I YFV. One Brazilian isolate exhibited, in addition to the 216-nt duplication, a deletion of a 40-nt repeated hairpin (RYF) motif (YF-XL-DeltaRYF). To investigate the biological significance of these 3' NCR rearrangements, YF-XL-DeltaRYF and YF-XL isolates, as well as other South American YFV isolates, were evaluated for three phenotypes: growth kinetics in cell culture, neuroinvasiveness in suckling mice, and ability to replicate and produce disseminated infections in Aedes aegypti mosquitoes. YF-XL-DeltaRYF and YF-XL isolates showed growth kinetics and neuroinvasive characteristics comparable to those of typical South American YFV isolates, and mosquito infectivity trials demonstrated that both types of 3' NCR variants were capable of replication and dissemination in a laboratory-adapted colony of A. aegypti.
Assuntos
Variação Genética , RNA não Traduzido/genética , RNA Viral/genética , Vírus da Febre Amarela/genética , Vírus da Febre Amarela/isolamento & purificação , Aedes/virologia , Animais , Sequência de Bases , Células Cultivadas , Modelos Animais de Doenças , Camundongos , Dados de Sequência Molecular , Conformação de Ácido Nucleico , Filogenia , RNA não Traduzido/química , RNA não Traduzido/fisiologia , RNA Viral/química , RNA Viral/fisiologia , Sequências Repetitivas de Ácido Nucleico , Deleção de Sequência , América do Sul , Febre Amarela/virologia , Vírus da Febre Amarela/classificação , Vírus da Febre Amarela/crescimento & desenvolvimento , Vírus da Febre Amarela/patogenicidadeRESUMO
The absence of urban yellow fever virus (YFV) in Bolivian cities has been attributed to the lack of competent urban mosquito vectors. Experiments with Aedes aegypti from Santa Cruz, Bolivia, demonstrated infection (100%), dissemination (20%), and transmission of a Bolivian YFV strain (CENETROP-322).