1. A lentiviral vector particle wherein the vector particle comprises a nucleic acid sequence comprising a sequence encoding: a. a first gene; b. a second gene; c. a third gene; d. an optional fourth gene, wherein the first, second, third and optional fourth genes are selected from the group consisting of Oct4, Klf4, Sox2, cMyc, Lin28, and Nanog; and wherein the first, second, third and optional fourth genes are not identical; e. a first ‘self-cleaving’ 2A peptide; f. a second ‘self-cleaving’ 2A peptide; and g. an internal ribosome entry site (IRES); wherein the nucleic acid sequence is operably linked to a promoter, wherein the sequences encoding the first, second, third and optional fourth genes, first and second ‘self-cleaving’ 2A peptides, and the IRES are transcribed from the promoter as a multi-cistronic RNA.