Methods and compositions related to high-titer pseudotyped retroviruses

The present invention concerns the methods and compositions related to pseudotyped viral vectors. Embodiments of the invention include pseudotyping expression cassettes that include nucleic acid elements for enhancing the titer of pseudotyped viral particles. Embodiments of the invention include novel methods and compositions related to making high titer pseudotyped retroviral vector compositions. A heterologous envelope glycoprotein is typically incorporated into the virus during the budding or virus production process. Certain embodiments of the invention include pseudotyped retroviral vectors comprising a heterologous envelope glycoprotein derived from a Jaagsiekte sheep retrovirus (JSRV env). Pseudotyped viruses or viral particles may have a modified host range that is influenced by the properties of the heterologous envelope glycoprotein. Thus, embodiments of the invention include improved methods and compositions related to pseudotyped viruses suitable for ex vivo and in vivo methods including gene transfer and other therapeutic and experimental methods.