RESUMO
We call into question the established dogma that viruses with envelopes and RNA genomes have limited stability by demonstrating the staggering long-term viability, â¼2 years, of chikungunya virus when stored in liquid environments at +4°C in the dark. We contend that our understanding of the infectivity of a variety of enveloped viruses requires a new approach to identify under standardized conditions the primary determinants of their viability.
Assuntos
Vírus Chikungunya , Temperatura Baixa , Manejo de Espécimes , Linhagem Celular , Vírus Chikungunya/genética , Escuridão , RNA ViralRESUMO
Flaviviruses are small RNA viruses that exhibit genetic and ecological diversity and a wide range of G+C content (GC%). We discovered that, amongst flaviviruses, the GC% of nucleotides encoding conserved amino acid (AA) residues was consistently higher than that of nucleotides encoding variable AAs. This intriguing phenomenon was also identified for a wide range of other viruses, and some non-viral evolutionary groups. Here, we analyse the possible mechanisms underlying this imbalanced nucleotide content (in particular the role of the specific G content and the AA composition in flaviviral genomes) and discuss its evolutionary implications. Our findings suggest that one of the most simple characteristics of the genetic code (i.e., the G or G+C content of codons) is linked with the evolutionary behavior of the corresponding encoded AAs.
Assuntos
Aminoácidos/genética , Composição de Bases/genética , Flavivirus/genética , Sequência de Aminoácidos , Evolução Molecular , FilogeniaRESUMO
Arboviruses have evolved a number of strategies to survive environmental challenges. This review examines the factors that may determine arbovirus emergence, provides examples of arboviruses that have emerged into new habitats, reviews the arbovirus situation in western Europe in detail, discusses potential arthropod vectors, and attempts to predict the risk for arbovirus emergence in the United Kingdom. We conclude that climate change is probably the most important requirement for the emergence of arthropodborne diseases such as dengue fever, yellow fever, Rift Valley fever, Japanese encephalitis, Crimean-Congo hemorrhagic fever, bluetongue, and African horse sickness in the United Kingdom. While other arboviruses, such as West Nile virus, Sindbis virus, Tahyna virus, and Louping ill virus, apparently circulate in the United Kingdom, they do not appear to present an imminent threat to humans or animals.
Assuntos
Infecções por Arbovirus/epidemiologia , Arbovírus/fisiologia , Doenças Transmissíveis Emergentes/epidemiologia , Doenças Transmissíveis Emergentes/virologia , Animais , Infecções por Arbovirus/virologia , Arbovírus/isolamento & purificação , Culicidae/virologia , Humanos , Reino Unido/epidemiologiaRESUMO
Control of West Nile virus (WNV) can only be effective if the vectors and reservoirs of the virus are identified and controlled. Although mosquitoes are the primary vectors, WNV has repeatedly been isolated from ticks. Therefore, tick-borne transmission studies were performed with an ixodid (Ixodes ricinus) and an argasid tick species (Ornithodoros moubata). Both species became infected after feeding upon viremic hosts, but I. ricinus ticks were unable to maintain the virus. In contrast, O. moubata ticks were infected for at least 132 days, and the infection was maintained through molting and a second bloodmeal. Infected O. moubata ticks transmitted the virus to rodent hosts, albeit at a low level. Moreover, the virus was nonsystemically transmitted between infected and uninfected O. moubata ticks co-fed upon uninfected hosts. Although ticks are unlikely to play a major role in WNV transmission, our findings suggest that some species have the potential to act as reservoirs for the virus.