The purpose of the present invention is to provide a lentiviral vector system having a higher titer, while sustaining an excellent retrograde transport ability particularly in the brain. The present invention relates to a kit for preparing a retrograde transport viral vector comprising: (1) a packaging plasmid containing the gag gene and the pol gene of HIV-1； (2) a packaging plasmid containing an accessory gene of HIV-1； (3) a transfer plasmid containing an target gene (a transgene)； and (4) an envelope plasmid containing, as an envelope gene, a gene encoding a fused polypeptide comprising a fused extracellular domain consisting of the N-terminal region of an extracellular domain of rabies virus glycoprotein (RV-G) and the C-terminal region of an extracellular domain of vesicular stomatitis virus glycoprotein (VSV-G), a transmembrane domain of RV-G orVSV-G, and an intracellular domain of VSV-G., and the like.
