Abstract: Our long-term aim is to develop a gene therapy approach for the prevention of laminitis in the contralateral foot of horses with major musculoskeletal injuries and non-weightbearing lameness. Objective: The goal of this study was to develop a practical method to efficiently deliver therapeutic proteins deep within the equine foot. Methods: Randomised in vivo experiment. Methods: We used recombinant adeno-associated viral vectors (rAAVs) to deliver marker genes using regional limb perfusion through the palmar digital artery of the horse. Results: Vector serotypes rAAV2/1, 2/8 and 2/9 all successfully transduced equine foot tissues and displayed similar levels and patterns of transduction. The regional distribution of transduction within the foot decreased with decreasing vector dose. The highest transduction values were seen in the sole and coronary regions and the lowest transduction values were detected in the dorsal hoof-wall region. The use of a surfactant-enriched vector diluent increased regional distribution of the vector and improved the transduction in the hoof-wall region. The hoof-wall region of the foot, which exhibited the lowest levels of transduction using saline as the vector diluent, displayed a dramatic increase in transduction when surfactant was included in the vector diluent (9- to 81-fold increase). In transduced tissues, no significant difference was observed between promoters (chicken β-actin vs. cytomegalovirus) for gene expression. All horses tested for vector-neutralising antibodies were positive for serotype-specific neutralising antibodies to rAAV2/5. Conclusions: The current experiments demonstrate that transgenes can be successfully delivered to the equine distal extremity using rAAV vectors and that serotypes 2/8, 2/9 and 2/1 can successfully transduce tissues of the equine foot. When the vector was diluted with surfactant-containing saline, the level of transduction increased dramatically. The increased level of transduction due to the addition of surfactant also improved the distribution pattern of transduction.
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The research study is focused on developing a gene therapy approach to prevent laminitis (a painful condition affecting horse’s feet) using gene-delivering viruses (recombinant adeno-associated viral vectors, rAAVs). These vectors were able to successfully introduce marker genes to equine foot tissues and the inclusion of a surfactant to the vector increased the effectiveness and distribution of the gene delivery.
Objective and Methods of Study
The research aimed to create a method for delivering therapeutic proteins deep within the foot of a horse. This will contribute to the broader goal of preventing laminitis in horses suffering from major musculoskeletal injuries.
The team utilized recombinant adeno-associated viral vectors (rAAVs) to convey marker genes into the horse’s foot. This was achieved through regional limb perfusion, a method of delivering medication to specific parts of the body, targeting the palmar digital artery of the horse.
Results of the Methods Used
Three types of vector serotypes (styles of the virus designed to carry the therapy), rAAV2/1, 2/8, and 2/9, were used. All three successfully transduced (transferred) genes into equine foot tissues and had comparable levels and patterns of transduction.
The researchers found variations in transduction levels within different regions of the horse’s foot. Maximum transduction was noted in the sole and the coronary regions of the foot, whereas minimum transduction was observed in the dorsal hoof-wall region.
To enhance transduction distribution and effectiveness in the hoof-wall region, a surfactant-enhanced vector diluent was used. This resulted in increased transduction levels, between 9 and 81-fold, in an area that initially showed low levels when saline was used as the vector diluent.
The study found no significant difference in gene expression between the two promoters used, chicken β-actin vs. cytomegalovirus.
Conclusion of Study
The researchers concluded that the transgenes can indeed be effectively introduced into a horse’s distal extremity (lower part of the limbs) using rAAV vectors.
The use of surfactant-enriched vector diluent significantly enhanced the transduction level and distribution within the foot.
Cite This Article
APA
Mason JB, Gurda BL, Van Wettere A, Engiles JB, Wilson JM, Richardson DW.
(2016).
Delivery and evaluation of recombinant adeno-associated viral vectors in the equine distal extremity for the treatment of laminitis.
Equine Vet J, 49(1), 79-86.
https://doi.org/10.1111/evj.12547
Department of Clinical Studies, New Bolton Center, School of Veterinary Medicine, University of Pennsylvania, Kennett Square, USA.
Gurda, B L
Gene Therapy Program, Department of Pathology and Laboratory Medicine, University of Pennsylvania, Philadelphia, USA.
Van Wettere, A
Utah Veterinary Diagnostic Laboratory, School of Veterinary Medicine, Utah State University, Logan, USA.
Engiles, J B
Department of Clinical Studies, New Bolton Center, School of Veterinary Medicine, University of Pennsylvania, Kennett Square, USA.
Wilson, J M
Gene Therapy Program, Department of Pathology and Laboratory Medicine, University of Pennsylvania, Philadelphia, USA.
Richardson, D W
Department of Clinical Studies, New Bolton Center, School of Veterinary Medicine, University of Pennsylvania, Kennett Square, USA.
MeSH Terms
Adenoviridae / physiology
Animals
Extremities
Foot Diseases / therapy
Foot Diseases / veterinary
Gene Expression Regulation, Enzymologic
Gene Expression Regulation, Viral
Genetic Therapy / methods
Genetic Therapy / veterinary
Genetic Vectors / metabolism
Hoof and Claw / pathology
Horse Diseases / therapy
Horses
Inflammation / therapy
Inflammation / veterinary
Transgenes
beta-Galactosidase / genetics
beta-Galactosidase / metabolism
Grant Funding
P30 AR069619 / NIAMS NIH HHS
P30 DK047757 / NIDDK NIH HHS
Conflict of Interest Statement
Authors’ declaration of interests. J.M. Wilson is an advisor to REGENXBIO, Dimension Therapeutics, Solid Gene Therapy, and Alexion, and is a founder of, holds equity in, and has a sponsored research agreement with REGENXBIO and Dimension Therapeutics; in addition, he is a consultant to several biopharmaceutical companies and is an inventor on patents licensed to various biopharmaceutical companies. All other authors declare that there are no conflicts of interest.
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