Fecha de publicación: 27/11/2002 Fuente: WIPO "miel" A retroviral vector comprises a functional splice donor site (FSDS) and a functional splice accepto (FSAS) site; wherein the FSDS and the FSAS flank a first nucleotide sequence of interest (NOI); wherein the FSDS is upstream of the FSAS; wherein the retroviral vector is derived from a retroviral pro-vector; wherein the retroviral pro-vector comprises a first nucleotide sequence (NS) capable o yielding the functional splice donor site (FSDS); a second NS capable of yielding the functional splice acceptor site (FSAS); a third NS capable of yielding a non-functional splice donor site (NFSDS); a fourth NS capable of yielding a non-functional splice site (NFSS); wherein the first NS is downstream of the second NS and wherein the third NS and fourth NS are upstream of the second NS; such that after reverse transcription of the retroviral pro-vector at a desired target site the retroviral vector is capable of being spliced. P:Mpret WIPOPA131326/ZA