The present invention concerns DNA constructs, recombinant viruses and vaccine compositions containing the recombinant viruses obtained. This invention also concerns an improvement of an expression vector of the live-attenuated yellow fever 17D virus. The present invention provides for the introduction of modifications in the expression cassette of heterologous proteins in the intergenic E/NS1 region of the yellow fever 17D vaccine virus. The two new functional domains inserted in the expression cassette were (1) a coding sequence for the N-glycosylation motif, located between the NS1 N-terminal motif and the heterologous protein and (2) a sequence which promoted the proteolytic cleavage, or not, of the recombinant protein in such a way as to release it from its C-terminal containing the transmembrane domains and, consequently, from its association with the membrane of the endoplasmatic reticulum - ER.
