RESUMO
The complete genome of West Nile (Sarafend) virus [WN(S)V] was sequenced. Phylogenetic trees utilizing the complete genomic sequence, capsid gene, envelope gene and NS5 gene/3' untranslated region of WN(S)V classified WN(S)V as a lineage II virus. A full-length infectious clone of WN(S)V with a point mutation in the glycosylation site of the envelope protein (pWNS-S154A) was constructed. Both growth kinetics and the mode of maturation were affected by this mutation. The titre of the pWNS-S154A virus was lower than the wild-type virus. This defect was corrected by the expression of wild-type envelope protein in trans. The pWNS-S154A virus matured intracellularly instead of at the plasma membrane as shown for the parental WN(S)V.
Assuntos
Genoma Viral , Proteínas do Envelope Viral/fisiologia , Vírus do Nilo Ocidental/fisiologia , Sequência de Aminoácidos , Animais , Linhagem Celular , Chlorocebus aethiops , Glicosilação , Dados de Sequência Molecular , Alinhamento de Sequência , Especificidade da Espécie , Células Vero , Proteínas do Envelope Viral/classificação , Proteínas do Envelope Viral/genética , Proteínas do Envelope Viral/metabolismo , Replicação Viral , Vírus do Nilo Ocidental/químicaRESUMO
West Nile (Sarafend) virus [WN(S)V] has been shown to egress by budding at the plasma membrane of infected cells. However, the region influencing this mode of virus release remains to be deciphered. In this study, we have constructed three chimeric clones in which specific regions of West Nile (Wengler) virus [WN(W)V] were replaced for the corresponding regions of WN(S)V in the full-length infectious clone of WN(S)V to define the region responsible for the cis-mode of WN(S)V maturation. The WN(W)V matures by the trans-mode. All of the resulting chimeric viruses were found to be infective. Transmission electron microscopy analyses performed in Vero cells infected with these chimeric viruses disclosed that the 5' end of the WN(S)V genome plays a major role in influencing the process of maturation at the plasma membrane.
Assuntos
Mapeamento Cromossômico/métodos , Clonagem Molecular/métodos , Genoma Viral , Replicação Viral/genética , Febre do Nilo Ocidental/genética , Febre do Nilo Ocidental/virologia , Vírus do Nilo Ocidental/crescimento & desenvolvimento , Vírus do Nilo Ocidental/genética , Animais , Chlorocebus aethiops , Células Vero , Febre do Nilo Ocidental/patologia , Vírus do Nilo Ocidental/ultraestruturaRESUMO
The envelope glycoprotein located at the outermost surface of the flavivirus particle mediates entry of virus into host cells. In this study, the involvement of domain III of West Nile virus (WNV-DIII) envelope protein in binding to host cell surface was investigated. WNV-DIII was first expressed as a recombinant protein and purified after a solubilization and refolding procedure. The refolded WNV-DIII protein displays a content of beta-sheets consistent with known homologous structures of other flavivirus envelope DIII, shown by using circular dichroism analysis. Purified recombinant WNV-DIII protein was able to inhibit WNV entry into Vero cells and C6/36 mosquito cells. Recombinant WNV-DIII only partially blocked the entry of dengue-2 (Den 2) virus into Vero cells. However, entry of Den 2 virus into C6/36 was blocked effectively by recombinant WNV-DIII. Murine polyclonal serum produced against recombinant WNV-DIII protein inhibited infection with WNV and to a much lesser extent with Den 2 virus, as demonstrated by plaque neutralization assays. Together these results provided strong evidence that immunoglobulin-like DIII of WNV envelope protein is responsible for binding to receptor on the surface of host cells. The data also suggest that similar attachment molecule(s) or receptor(s) were used by WNV and Den 2 virus for entry into C6/36 mosquito cells.