Extended transgene expression from a nonintegrating adenoviral vector containing retroviral elements.
We studied the effects of specific retroviral elements in a first-generation serotype 5 adenoviral (Ad5) vector, AdLTR(2)EF1alpha-hEPO. This vector contains 858 base pair (bp) [251-bp envelope sequence plus 607-bp long-terminal repeat (LTR)] from Moloney murine leukemia virus (MoMLV), upstream of the human elongation factor-1alpha (EF1alpha) promoter and human erythropoietin (hEPO) cDNA, with the LTR sequence downstream of the polyadenylation signal. We compared expression of AdLTR(2)EF1alpha-hEPO with corresponding expressions of two conventional Ad5 vectors, AdEF1alpha-hEPO and AdCMV-hEPO, in vivo in submandibular glands in rats. Both the conventional vectors yielded low serum hEPO levels by day 7, and little change in hematocrits. In contrast, after receiving AdLTR(2)EF1alpha-hEPO, the rats showed elevated hEPO levels and hematocrits for 1-3 months. In vitro studies showed that the integration efficiencies of all the vectors were similar (approximately 10(-3)). Approximately 0.1% of the vector genomes were present 1 year after delivery in the case of each of the three vectors, primarily as intact linear double-strand DNA. The unique results seen with AdLTR(2)EF1alpha-hEPO are partly because of LTR enhancer activity. However, other cis-acting activity, which is not immunomodulatory but nevertheless influences promoter methylation, appears to be involved. A vector such as AdLTR(2)EF1alpha-hEPO may prove useful in clinical applications in which extended, but not "permanent," transgene expression is desirable.
Zheng
Changyu
C
Molecular Physiology and Therapeutics Branch, National Institute of Dental and Craniofacial Research, National Institutes of Health, Department of Health and Human Services, Bethesda, Maryland 20892-1190, USA.
Vitolo
Joseph M
JM
Zhang
Weitian
W
Mineshiba
Fumi
F
Chiorini
John A
JA
Baum
Bruce J
BJ
D000256:Adenoviridae / Q000235:genetics*; D000818:Animals; D004921:Erythropoietin / Q000235:genetics; D005260:Female; D005786:Gene Expression Regulation; D005822:Genetic Vectors; D006801:Humans; D008979:Moloney murine leukemia virus / Q000235:genetics; D011401:Promoter Regions, Genetic; D051381:Rats; D017208:Rats, Wistar; D012190:Retroviridae / Q000235:genetics; D013363:Submandibular Gland / Q000378:metabolism; D020079:Terminal Repeat Sequences; D019076:Transgenes
D004921:Erythropoietin