Strain-specific rate of shutdown of CMV enhancer activity in murine liver confirmed by use of persistent [E1(-), E2b(-)] adenoviral vectors.
The systemic delivery of [E1(-)] adenoviral (Ad) vectors encoding a transgene results in efficient viral uptake and abundant transgene expression in the liver. However, [E1(-)]Ad vector persistence is transient due to cytotoxic T lymphocyte (CTL)-mediated loss of the Ad-infected cells. Our laboratory has previously demonstrated that additional modifications to the [E1(-)]Ad vector genome, by deletion of the Ad E2b genes, significantly decreased virus-genome-derived gene expression and simultaneously improved the long-term performance of the resultant [E1(-), E2b(-)]Ad vector. In this study, we confirmed that [E1(-), E2b(-)]Ad vector genomes could persist equally well in C57Bl/6 or Balb/c mouse hepatocytes. Despite vector genome persistence, we observed a strain-dependent variability in the duration of CMV enhancer/promoter-driven transgene expression in the liver. While Balb/c mice rapidly shut down [E1(-), E2b(-)]Ad-derived transgene expression, C57Bl/6 mice allowed for prolonged transgene expression. This occurred even when both strains were crossed into a severe combined immune-deficient background, demonstrating that host adaptive immune responses are not responsible for the phenomenon. Furthermore, differential methylation of the CMV enhancer/promoter was also not demonstrated in either strain of mouse, eliminating this mechanism as causative. Thus, alternative mechanisms for this phenomenon are discussed.
Everett
R S
RS
Department of Pediatrics, Division of Medical Genetics, Duke University Medical Center, Durham, NC 27705, USA.
Evans
H K
HK
Hodges
B L
BL
Ding
E Y
EY
Serra
D M
DM
Amalfitano
A
A
D000256:Adenoviridae / Q000235:genetics*; D000818:Animals; D001483:Base Sequence; D003587:Cytomegalovirus / Q000235:genetics*; D019175:DNA Methylation; D004742:Enhancer Elements, Genetic; D004797:Enzyme-Linked Immunosorbent Assay; D005822:Genetic Vectors; D006801:Humans; D007763:Lac Operon; D008099:Liver / Q000378:metabolism*; D051379:Mice; D008807:Mice, Inbred BALB C; D008969:Molecular Sequence Data; D013045:Species Specificity; D019076:Transgenes