Helper-dependent adenoviral gene therapy mediates long-term correction of the clotting defect in the canine hemophilia A model.
BACKGROUND
Adenoviral vector-mediated gene therapy might have potential for long-term correction of the monogenic disease hemophilia A.


OBJECTIVE
In this study, we tested the efficacy of administering a helper-dependent adenoviral vector (HDV) designed for maximal liver-restricted canine factor VIII (cFVIII) expression on three out-bred hemophilia A dogs.


METHODS
Three FVIII-deficient animals from the University of North Carolina colony were injected with 1 x 10(12) (Dog A), and 3 x 10(12) (Dog B and C) vp kg(-1) helper-dependent adenoviral vector, and we performed systematic analysis of toxicity, persistence of therapeutic gene expression, and molecular analysis of gene transfer.


RESULTS
We observed acute dose-dependent elevation in liver enzymes and thrombocytopenia after injection, although both were transient and resolved within 2 weeks. The whole blood clotting time (WBCT), plasma FVIII concentration, FVIII activity, and activated partial thromboplastin time in all animals improved significantly after treatment, and two animals receiving a higher dose reached near normal WBCT with low-level FVIII activity until terminal sacrifice at 3 months, and 2 years. Importantly, the treated dogs suffered no bleeding events after injection. Moreover, we observed persistent vector-specific DNA and RNA in liver tissue collected from one high-dose animal at days 18 and 79, and could not detect the formation of inhibitory antibodies.


CONCLUSIONS
Although vector-associated toxicity remains an obstacle, a single injection of HDV led to long-term transgene expression and vector persistence in two FVIII-deficient animals with conversion of their severe phenotype to a moderate one.
McCORMACK
W M
WM
Department of Molecular and Human Genetics.
Seiler
M P
MP
Department of Molecular and Human Genetics.|Interdepartmental Program in Cell and Molecular Biology, Baylor College of Medicine, Houston, TX.
Bertin
T K
TK
Department of Molecular and Human Genetics.
Ubhayakar
K
K
Department of Molecular and Human Genetics.
Palmer
D J
DJ
Department of Molecular and Human Genetics.
Ng
P
P
Department of Molecular and Human Genetics.
Nichols
T C
TC
Pathology and Laboratory Medicine, University of North Carolina, Chapel Hill, NC.
Lee
B
B
Department of Molecular and Human Genetics.|The Howard Hughes Medical Institute, Baylor College of Medicine, Houston, TX, USA.
D000256:Adenoviridae / Q000235:genetics*; D000818:Animals; D001777:Blood Coagulation; D004195:Disease Models, Animal; D004285:Dogs; D005169:Factor VIII / Q000235:genetics* / Q000378:metabolism / Q000627:therapeutic use; D015316:Genetic Therapy / Q000379:methods*; D005822:Genetic Vectors / Q000633:toxicity; D006467:Hemophilia A / Q000097:blood / Q000235:genetics / Q000628:therapy*; D008099:Liver / Q000378:metabolism; D009154:Mutation; D010314:Partial Thromboplastin Time; D014914:Whole Blood Coagulation Time
D005169:Factor VIII