title: Equal potency of gammaretroviral and lentiviral SIN vectors for expression of O6-methylguanine-DNA methyltransferase in hematopoietic cells.
abstract: Severe adverse events related to insertional mutagenesis have reinforced interest in self-inactivating (SIN) retroviral vectors lacking enhancer-promoter sequences in the long terminal repeats (LTRs). Here, we have compared the potency of gammaretroviral and lentiviral vectors expressing the P140K mutant of O(6)-methylguanine-DNA methyltransferase (MGMT). MGMT-P140K is a clinically relevant selection marker that mediates a strong survival advantage in hematopoietic cells exposed to alkylating agents. We designed gammaretroviral and lentiviral vectors that contained identical enhancer-promoter sequences located either in the LTR or downstream of the packaging region, for internal initiation of transcription from SIN backbones. Gammaretroviral vectors with intact LTRs containing enhancer-promoter sequences showed both higher titers and higher expression levels than the lentiviral counterparts, likely a result of suboptimal RNA processing of the lentiviral leader region. In the SIN context, gammaretroviral and lentiviral vectors with comparable internal cassettes had similar expression properties. Interestingly, gammaretroviral SIN vectors pseudotyped with RD114/TR had a higher transduction efficiency on proliferating human CD34(+) cells than lentiviral counterparts. These results encourage further investigations into the formation of retroviral hybrid vectors that combine the desired properties of high efficiency and increased biosafety.
authors.affiliation: Department of Hematology, Hemostaseology, and Oncology, Hannover Medical School, Germany.
authors.forename: Axel
authors.initials: A
authors.lastname: Schambach
authors.forename: Jens
authors.initials: J
authors.lastname: Bohne
authors.forename: Saurabh
authors.initials: S
authors.lastname: Chandra
authors.forename: Elke
authors.initials: E
authors.lastname: Will
authors.forename: Geoffrey P
authors.initials: GP
authors.lastname: Margison
authors.forename: David A
authors.initials: DA
authors.lastname: Williams
authors.forename: Christopher
authors.initials: C
authors.lastname: Baum
mesh_terms: D000818:Animals; D002478:Cells, Cultured; D015967:Gene Expression Regulation, Viral / Q000502:physiology*; D005822:Genetic Vectors; D006412:Hematopoietic Stem Cells / Q000201:enzymology* / Q000821:virology; D006801:Humans; D016086:Lentivirus / Q000235:genetics*; D009052:Leukemia Virus, Murine / Q000235:genetics*; D051379:Mice; D008810:Mice, Inbred C57BL; D016254:Mutagenesis, Insertional; D019853:O(6)-Methylguanine-DNA Methyltransferase / Q000096:biosynthesis* / Q000235:genetics* / Q000502:physiology; D012323:RNA Processing, Post-Transcriptional; D014161:Transduction, Genetic
chemical_list: D019853:O(6)-Methylguanine-DNA Methyltransferase