An adenoviral vector deleted for all viral coding sequences results in enhanced safety and extended expression of a leptin transgene

An adenoviral vector deleted for all viral coding sequences results in enhanced safety and extended expression of a leptin transgene

^*Department of Human Genetics; ^‡Department of Laboratory Animal Resources, and ^§Safety Assessment, Merck Research Laboratories, West Point, PA 19486; ^¶Departments of Biology and Pathology, McMaster University, Hamilton, ON, Canada L8S 4K1; and ^‖Department of Molecular and Human Genetics, Baylor College of Medicine, One Baylor Plaza, Houston, TX 77030

Contributed by C. Thomas Caskey

Abstract

Adenoviral (Ad)-mediated in vivo gene transfer and expression are limited in part by cellular immune responses to viral-encoded proteins and/or transgene immunogenicity. In an attempt to diminish the former responses, we have previously developed and described helper-dependent (HD) Ad vectors in which the viral protein coding sequences are completely eliminated. These HD vectors have up to 37 kb insert capacity, are easily propagated in a Cre recombinase-based system, and can be produced to high concentration and purity (>99.9% helper-free vector). In this study, we compared safety and efficacy of leptin gene delivery mediated by an HD vector (HD-leptin) and a first-generation E1-deleted Ad vector (Ad-leptin) in normal lean and ob/ob (leptin-deficient) mice. In contrast to evidence of liver toxicity, inflammation, and cellular infiltration observed with Ad-leptin delivery in mice, HD-leptin delivery was associated with a significant improvement in associated safety/toxicity and resulted in efficient gene delivery, prolonged elevation of serum leptin levels, and associated weight loss. The greater safety, efficient gene delivery, and increased insert capacity of HD vectors are significant improvements over current Ad vectors and represent favorable features especially for clinical gene therapy applications.

Footnotes

↵ † To whom reprint requests should be addressed. e-mail: morsy{at}merck.com.
ABBREVIATIONS:

Ad,

adenoviral;

HD,

helper-dependent;

Ad-leptin,

leptin Ad vector;

HD-leptin,

leptin HD;

ITR,

inverted terminal repeat;

β-gal,

β-galactosidase;

AST,

aspartate aminotransferase;

ALT,

alanine aminotransferase;

HCMV,

human cytomegalovirus