Consistent, persistent expression from modified retroviral vectors in murine hematopoietic stem cells.
Retroviral vectors based on the Moloney murine leukemia virus (MoMuLV) have shown inconsistent levels and duration of expression as well as a propensity for the acquisition of de novo methylation in vivo. MoMuLV-based vectors are known to contain sequences that are capable of suppressing or preventing expression from the long terminal repeat. Previously, we constructed a series of modified retroviral vectors and showed that they function significantly better than MoMuLV-based vectors in vitro. To test the efficacy of the modified vectors in hematopoietic stem cells in vivo, we examined gene expression and proviral methylation in differentiated hematopoietic colonies formed in the spleens of mice after serial transplantation with transduced bone marrow (2 degreesCFU-S). We found a significant increase in the frequency of expression with our modified vectors (>90% expression in vector DNA containing 2 degreesCFU-S) over the frequency observed with the standard MoMuLV-based vector (28% expression in vector containing 2 degreesCFU-S). Expression from the modified vectors was highly consistent, with expression in >50% of the vector-containing 2 degreesCFU-S from all 20 transplant recipients analyzed, whereas expression from the standard MoMuLV-based vector was inconsistent, with expression in 0-10% of the vector containing 2 degreesCFU-S from 8 recipients and expression in >50% of the vector-containing 2 degreesCFU-S from 4 other recipients. In addition, we established that the modified vectors had a lower level of DNA methylation than the control vector. These findings represent significant advances in the development and evaluation of effective retroviral vectors for application in vivo.
Robbins
P B
PB
Department of Molecular Microbiology and Immunology, Division of Research Immunology/Bone Marrow Transplantation, Childrens Hospital Los Angeles, University of Southern California School of Medicine, Los Angeles, CA 90027, USA.
Skelton
D C
DC
Yu
X J
XJ
Halene
S
S
Leonard
E H
EH
Kohn
D B
DB
D000818:Animals; D001483:Base Sequence; D016026:Bone Marrow Transplantation; D003114:Colony-Forming Units Assay; D019175:DNA Methylation; D017931:DNA Primers / Q000235:genetics; D004274:DNA, Recombinant / Q000235:genetics / Q000378:metabolism; D005260:Female; D018703:Founder Effect; D015870:Gene Expression; D018014:Gene Transfer Techniques; D005822:Genetic Vectors; D006412:Hematopoietic Stem Cells / Q000166:cytology / Q000378:metabolism*; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D008979:Moloney murine leukemia virus / Q000235:genetics; D012091:Repetitive Sequences, Nucleic Acid; D012190:Retroviridae / Q000235:genetics*; D014161:Transduction, Genetic; D014185:Transplantation, Isogeneic; D016662:Virus Integration / Q000235:genetics
D017931:DNA Primers; D004274:DNA, Recombinant