Expression of foreign protein epitopes at the surface of recombinant yellow fever 17D viruses based on three-dimensional modeling of its envelope protein

The yellow fever (YF) 17D vaccine is a live attenuated virus, and its genetic manipulation constitutes a new platform for vaccine development. In this article, we review one of the possible approaches to enable this development, which is the insertion of foreign protein epitopes into different locations of the genome. We describe the three-dimensional (3D) modeling of the YF 17D virus E protein structure based on tick-borne encephalitis (TBE) and the identification of a potential insertion site located at the YF 17D fg loop. Further 3D analysis revealed that it is possible to accommodate inserts of different sizes and amino acid composition in the flavivirus E protein fg loop. We demonstrate that seven YF 17D viruses bearing foreign epitopes that vary in sequence and length show differential growth characteristics in cell culture. The testing of recombinant viruses for mouse neurovirulence suggests that insertions at the 17D E protein fg loop do not compromise the attenuated phenotype of YF 17D virus, further confirming the potential use of this site for the development of new live attenuated 17D virus-based vaccines.