Retroviral vector integration deregulates gene expression but has no consequence on the biology and function of transplanted T cells.
The use of retroviral vectors in gene therapy has raised safety concerns for the genotoxic risk associated with their uncontrolled insertion into the human genome. We have analyzed the consequences of retroviral transduction in T cells from leukemic patients treated with allogeneic stem cell transplantation and donor lymphocytes genetically modified with a suicide gene (HSV-TK). Retroviral vectors integrate preferentially within or near transcribed regions of the genome, with a preference for sequences around promoters and for genes active in T cells at the time of transduction. Quantitative transcript analysis shows that one fifth of these integrations affect the expression of nearby genes. However, transduced T cell populations maintain remarkably stable gene expression profiles, phenotype, biological functions, and immune repertoire in vivo, with no evidence of clonal selection up to 9 yr after administration. Analysis of integrated proviruses in transduced cells before and after transplantation indicates that integrations interfering with normal T cell function are more likely to lead to clonal ablation than expansion in vivo. Despite the potentially dangerous interactions with the T cell genome, retroviral integration has therefore little consequence on the safety and efficacy of T cell transplantation.
Recchia
Alessandra
A
Cancer Immunotherapy and Gene Therapy Program, and Bone Marrow Transplantation Unit, Istituto Scientifico H. San Raffaele, Via Olgettina 58, 20132 Milan, Italy.
Bonini
Chiara
C
Magnani
Zulma
Z
Urbinati
Fabrizia
F
Sartori
Daniela
D
Muraro
Sara
S
Tagliafico
Enrico
E
Bondanza
Attilio
A
Stanghellini
Maria Teresa Lupo
MT
Bernardi
Massimo
M
Pescarollo
Alessandra
A
Ciceri
Fabio
F
Bordignon
Claudio
C
Mavilio
Fulvio
F
D000293:Adolescent; D000328:Adult; D017690:Cell Transplantation; D002986:Clinical Trials as Topic; D003001:Cloning, Molecular; D018076:DNA, Complementary / Q000378:metabolism; D005260:Female; D015870:Gene Expression; D005786:Gene Expression Regulation; D015967:Gene Expression Regulation, Viral; D015316:Genetic Therapy / Q000379:methods; D005822:Genetic Vectors; D016678:Genome; D006086:Graft vs Host Disease; D006801:Humans; D007107:Immune System; D016130:Immunophenotyping; D007938:Leukemia / Q000235:genetics; D015464:Leukemia, Myelogenous, Chronic, BCR-ABL Positive / Q000628:therapy; D007963:Leukocytes, Mononuclear / Q000166:cytology / Q000378:metabolism; D008214:Lymphocytes / Q000378:metabolism; D008297:Male; D008875:Middle Aged; D008954:Models, Biological; D008957:Models, Genetic; D016296:Mutagenesis; D010641:Phenotype; D011533:Proviruses / Q000235:genetics; D012333:RNA, Messenger / Q000378:metabolism; D012190:Retroviridae / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction; D033581:Stem Cell Transplantation; D013601:T-Lymphocytes / Q000378:metabolism* / Q000637:transplantation; D013997:Time Factors
D018076:DNA, Complementary; D012333:RNA, Messenger