Safety assessment of intradiscal gene therapy II: effect of dosing and vector choice.
METHODS
Clinical, biochemical, and histologic analysis was performed after in vivo delivery of cDNA encoding various anabolic cytokines and marker genes to the lumbar epidural space of New Zealand white rabbits, using both adenoviral and adeno-associated viral vectors.


OBJECTIVE
To mimic errant or misplaced doses of gene therapy to better ascertain the potential risks associated with alternative vectors and transgene products with regard to their application to problems of the intervertebral disc.


BACKGROUND
Work done with several anabolic cytokines including bone morphogenic proteins and transforming growth factors, has demonstrated the potential of gene therapy. Recently, data has been published demonstrating that improperly dosed or delivered adenoviral-mediated gene therapy within the subarachnoid space can result in significant morbidity in rabbits. There are currently no studies examining the effect of these errors within the epidural space or using an adeno-associated viral (AAV) vector.


METHODS
Using either adenoviral or AAV vectors, complementary DNA (cDNA) encoding anabolic cytokines bone morphogenic protein-2 (BMP-2) and transforming growth factor-beta 1 and marker proteins LacZ and green fluorescent protein were injected into the epidural space of 37 New Zealand white rabbits at the L5/6 level. Rabbits were then observed clinically for up to 6 weeks, after which the rabbits were sacrificed in order to perform a comprehensive biochemical and histologic analysis.


RESULTS
Following adenoviral-mediated delivery of anabolic cytokine cDNA, up to eighty percent of rabbits demonstrated significant clinical, biochemical, and histologic morbidity. Conversely, AAV-mediated delivery of any cDNA and adenoviral-mediated delivery of marker protein cDNA resulted in no clinical, histologic, or biochemical morbidity.


CONCLUSIONS
Properly dosed and directed gene therapy seems to be both safe and potentially efficacious. This study suggests that side effects of gene therapy may be due to a combination of dosing, transgene product, and vector choice, and that newer AAV vectors may reduce these side-effects and decrease the risk of this technology.
Department of Orthopaedic Surgery, Ferguson Laboratory for Orthopaedic Research, University of Pittsburgh Medical Center, Pittsburgh, PA, USA.
Eric A
EA
Levicoff
Joseph S
JS
Kim
Satoshi
S
Sobajima
Corey J
CJ
Wallach
James W
JW
Larson
Paul D
PD
Robbins
Xiao
X
Xiao
Li
L
Juan
Gianluca
G
Vadala
Lars G
LG
Gilbertson
James D
JD
Kang
D000256:Adenoviridae / Q000235:genetics*; D000818:Animals; D055396:Bone Morphogenetic Protein 2; D019485:Bone Morphogenetic Proteins / Q000235:genetics; D018076:DNA, Complementary / Q000008:administration & dosage / Q000627:therapeutic use*; D000229:Dependovirus / Q000235:genetics*; D004195:Disease Models, Animal; D004824:Epidural Space; D005260:Female; D015316:Genetic Therapy / Q000009:adverse effects* / Q000379:methods*; D005822:Genetic Vectors; D049452:Green Fluorescent Proteins / Q000235:genetics; D007278:Injections, Spinal; D007763:Lac Operon / Q000235:genetics; D008159:Lumbar Vertebrae; D011817:Rabbits; D013122:Spinal Diseases / Q000628:therapy*; D016212:Transforming Growth Factor beta / Q000235:genetics; D053773:Transforming Growth Factor beta1 / Q000235:genetics
D055396:Bone Morphogenetic Protein 2; D019485:Bone Morphogenetic Proteins; D018076:DNA, Complementary; D016212:Transforming Growth Factor beta; D053773:Transforming Growth Factor beta1; D049452:Green Fluorescent Proteins