This invention provides a retroviral packaging cell comprising a suitable mammalian cell having therein (i) a first recombinant nucleic acid comprising MMLV gag and pol genes and a selectable marker, and (ii) a second recombinant nucleic acid comprising RD114 envelope gene and a selectable marker, wherein the MMLV gag and pol genes and the RD114 envelope gene are stably expressed in the cell. This invention further provides related production methods, virions and kits.