The predicted structural features of NS4 resemble those of a transcription factor of the bZip family with a basic domain followed by a leucine zipper motif [70] . Thus, NS4 may function as a nucleic acid binding protein and either repress or enhance transcription of genes linked directly or indirectly to the IFN response of the cell. However, a BTV-8 recombinant virus (BTV-8DLZNS4) expressing an NS4 with all the 4 leucine residues forming the putative leucine zipper mutated (into either glutamine or serine) replicated as efficiently as BTV-8 wt in cells pre-treated with IFN (data not shown). Thus, more studies will be necessary to explore this possibility.