The 15 amino acid residues preceding the amino terminus of the envelope protein in the yellow fever virus polyprotein precursor act as a signal peptide

The key amino acids of E protein involved in early flavivirus infection: viral entry

Flaviviruses are enveloped viruses that infect multiple hosts. Envelope proteins are the outermost proteins in the structure of flaviviruses and mediate viral infection. Studies indicate that flaviviruses mainly use envelope proteins to bind to cell attachment receptors and endocytic receptors for the entry step. Here, we present current findings regarding key envelope protein amino acids that participate in the flavivirus early infection process. Among these sites, most are located in special positions of the protein structure, such as the α-helix in the stem region and the hinge region between domains I and II, motifs that potentially affect the interaction between different domains. Some of these sites are located in positions involved in conformational changes in envelope proteins. In summary, we summarize and discuss the key envelope protein residues that affect the entry process of flaviviruses, including the process of their discovery and the mechanisms that affect early infection.

Mutation in a 17D-204 vaccine substrain-specific envelope protein epitope alters the pathogenesis of yellow fever virus in mice

The heterogeneous nature of the yellow fever (YF) 17D-204 vaccine virus population was exploited in this study to isolate virus variants able to escape neutralization by the 17D-204 vaccine-specific MAb 864. The conformational change on the virus surface that resulted in the loss of the MAb 864-defined epitope was effected in each variant by a single amino acid mutation in the envelope (E) protein at either position E-305 or E-325. Interestingly, both positions were mutated during attenuation of the 17D-204 vaccine substrain from the wildtype Asibi strain. The mutations in several of the variants represented reversion to the wildtype Asibi virus sequence consistent with loss of a 17D-204 substrain-specific epitope. The majority of the variant viruses were shown to have altered mouse neurovirulence phenotypes, ranging from complete avirulence through to increased virulence. The avirulent variants are the first flavivirus MAb-neutralization-resistant variants to be attenuated for neurovirulence in the adult mouse model. Overall, the results indicate that the E protein epitope recognized by MAb 864 defines a functionally important region that encodes major molecular determinants of YF virus pathogenesis in vivo.