Extended transgene expression from a nonintegrating adenoviral vector containing retroviral elements

Area of Science:

• Gene Therapy
• Molecular Biology
• Virology

Background:

• First-generation serotype 5 adenoviral (Ad5) vectors are widely used for gene delivery.
• Conventional Ad5 vectors often exhibit transient transgene expression.
• Retroviral elements can influence gene expression kinetics.

Purpose of the Study:

• To evaluate the efficacy of a novel Ad5 vector (AdLTR(2)EF1alpha-hEPO) containing Moloney murine leukemia virus (MoMLV) retroviral elements for enhanced transgene expression.
• To compare the in vivo expression profile of AdLTR(2)EF1alpha-hEPO with conventional Ad5 vectors (AdEF1alpha-hEPO and AdCMV-hEPO).

Main Methods:

• Construction of AdLTR(2)EF1alpha-hEPO incorporating MoMLV LTR and envelope sequences.
• In vivo administration of AdLTR(2)EF1alpha-hEPO and control vectors into rat submandibular glands.
• Quantification of serum human erythropoietin (hEPO) levels and hematocrit.
• In vitro assessment of vector integration efficiency and persistence of vector genomes.

Main Results:

• AdLTR(2)EF1alpha-hEPO administration resulted in elevated serum hEPO levels and hematocrits sustained for 1-3 months in rats.
• Conventional Ad5 vectors showed low hEPO levels and minimal hematocrit changes by day 7.
• All vectors exhibited similar integration efficiencies (approx. 10(-3)) and vector genome persistence (approx. 0.1% at 1 year).

Conclusions:

• The incorporation of specific retroviral elements, particularly LTR enhancer activity, significantly prolonged transgene expression from the Ad5 vector.
• The AdLTR(2)EF1alpha-hEPO vector provides extended, non-permanent transgene expression, suitable for specific clinical applications.
• Further investigation into cis-acting elements influencing promoter methylation is warranted.