title: Alpharetroviral self-inactivating vectors: long-term transgene expression in murine hematopoietic cells and low genotoxicity.
abstract: Comparative integrome analyses have highlighted alpharetroviral vectors with a relatively neutral, and thus favorable, integration spectrum. However, previous studies used alpharetroviral vectors harboring viral coding sequences and intact long-terminal repeats (LTRs). We recently developed self-inactivating (SIN) alpharetroviral vectors with an advanced split-packaging design. In a murine bone marrow (BM) transplantation model we now compared alpharetroviral, gammaretroviral, and lentiviral SIN vectors and showed that all vectors transduced hematopoietic stem cells (HSCs), leading to comparable, sustained multilineage transgene expression in primary and secondary transplanted mice. Alpharetroviral integrations were decreased near transcription start sites, CpG islands, and potential cancer genes compared with gammaretroviral, and decreased in genes compared with lentiviral integrations. Analyzing the transcriptome and intragenic integrations in engrafting cells, we observed stronger correlations between in-gene integration targeting and transcriptional activity for gammaretroviral and lentiviral vectors than for alpharetroviral vectors. Importantly, the relatively "extragenic" alpharetroviral integration pattern still supported long-term transgene expression upon serial transplantation. Furthermore, sensitive genotoxicity studies revealed a decreased immortalization incidence compared with gammaretroviral and lentiviral SIN vectors. We conclude that alpharetroviral SIN vectors have a favorable integration pattern which lowers the risk of insertional mutagenesis while supporting long-term transgene expression in the progeny of transplanted HSCs.
authors.affiliation: Institute of Experimental Hematology, Hannover Medical School, Hannover, Germany.
authors.forename: Julia D
authors.initials: JD
authors.lastname: Suerth
authors.forename: Tobias
authors.initials: T
authors.lastname: Maetzig
authors.forename: Martijn H
authors.initials: MH
authors.lastname: Brugman
authors.forename: Niels
authors.initials: N
authors.lastname: Heinz
authors.forename: Jens-Uwe
authors.initials: JU
authors.lastname: Appelt
authors.forename: Kerstin B
authors.initials: KB
authors.lastname: Kaufmann
authors.forename: Manfred
authors.initials: M
authors.lastname: Schmidt
authors.forename: Manuel
authors.initials: M
authors.lastname: Grez
authors.forename: Ute
authors.initials: U
authors.lastname: Modlich
authors.forename: Christopher
authors.initials: C
authors.lastname: Baum
authors.forename: Axel
authors.initials: A
authors.lastname: Schambach
mesh_terms: D001355:Alpharetrovirus / Q000235:genetics*; D000818:Animals; D002460:Cell Line; D018899:CpG Islands; D017988:Gammaretrovirus / Q000235:genetics; D018390:Gene Targeting; D005822:Genetic Vectors; D018380:Hematopoietic Stem Cell Transplantation; D006412:Hematopoietic Stem Cells / Q000166:cytology / Q000378:metabolism*; D006801:Humans; D016086:Lentivirus / Q000235:genetics; D051379:Mice; D016254:Mutagenesis, Insertional; D012307:Risk Factors; D020079:Terminal Repeat Sequences; D024363:Transcription Initiation Site; D059467:Transcriptome / Q000235:genetics; D014161:Transduction, Genetic; D019076:Transgenes