Vector integration is nonrandom and clustered and influences the fate of lymphopoiesis in SCID-X1 gene therapy.
Recent reports have challenged the notion that retroviruses and retroviral vectors integrate randomly into the host genome. These reports pointed to a strong bias toward integration in and near gene coding regions and, for gammaretroviral vectors, around transcription start sites. Here, we report the results obtained from a large-scale mapping of 572 retroviral integration sites (RISs) isolated from cells of 9 patients with X-linked SCID (SCID-X1) treated with a retrovirus-based gene therapy protocol. Our data showed that two-thirds of insertions occurred in or very near to genes, of which more than half were highly expressed in CD34(+) progenitor cells. Strikingly, one-fourth of all integrations were clustered as common integration sites (CISs). The highly significant incidence of CISs in circulating T cells and the nature of their locations indicate that insertion in many gene loci has an influence on cell engraftment, survival, and proliferation. Beyond the observed cases of insertional mutagenesis in 3 patients, these data help to elucidate the relationship between vector insertion and long-term in vivo selection of transduced cells in human patients with SCID-X1.
Institute for Molecular Medicine and Cell Research and Department of Internal Medicine I, German Cancer Research Center, University of Freiburg, Freiburg, Germany.
Annette
A
Deichmann
Salima
S
Hacein-Bey-Abina
Manfred
M
Schmidt
Alexandrine
A
Garrigue
Martijn H
MH
Brugman
Jingqiong
J
Hu
Hanno
H
Glimm
Gabor
G
Gyapay
Bernard
B
Prum
Christopher C
CC
Fraser
Nicolas
N
Fischer
Kerstin
K
Schwarzwaelder
Maria-Luise
ML
Siegler
Dick
D
de Ridder
Karin
K
Pike-Overzet
Steven J
SJ
Howe
Adrian J
AJ
Thrasher
Gerard
G
Wagemaker
Ulrich
U
Abel
Frank J T
FJ
Staal
Eric
E
Delabesse
Jean-Luc
JL
Villeval
Bruce
B
Aronow
Christophe
C
Hue
Claudia
C
Prinz
Manuela
M
Wissler
Chuck
C
Klanke
Jean
J
Weissenbach
Ian
I
Alexander
Alain
A
Fischer
Christof
C
von Kalle
Marina
M
Cavazzana-Calvo
D018952:Antigens, CD34; D049109:Cell Proliferation; D002470:Cell Survival / Q000235:genetics; D017988:Gammaretrovirus; D015316:Genetic Therapy; D005822:Genetic Vectors; D015894:Genome, Human; D006412:Hematopoietic Stem Cells / Q000378:metabolism; D006801:Humans; D038041:Lymphopoiesis / Q000235:genetics*; D016254:Mutagenesis, Insertional; D040641:Quantitative Trait Loci; D013601:T-Lymphocytes; D013997:Time Factors; D016662:Virus Integration / Q000235:genetics*; D053632:X-Linked Combined Immunodeficiency Diseases / Q000235:genetics / Q000628:therapy*
D018952:Antigens, CD34