The goal of this proposal is to explore ways to generate a novel AAV vector to overcome the barrier of pre- existing vector neutralizing antibodies (NAbs) to achieve efficient gene transfer in vivo. In vivo delivery of AAV vectors has shown promise in a variety of pre-clinical and clinical models of inherited disorders. The major challenges to date involve host immune responses and poor transduction efficiency due to limited vector tropism and poor delivery of the vector to the target cell. AAV serotype 8 (AAVS) has been identified as the best Clinical Candidate vector for liver-directed gene transfer and is currenfiy being evaluated in a human clinical trial for gene therapy of hemophilia B. Much is still being learned about host-vector immune interactions such as the effect of innate immunity and activation of T cells and B cells against the vector and its transgene product. One of the most important aspects of host immunity is the impact of neutralizing antibodies (NAb) on transduction efficiency. NAb against the AAV vector capsid results in substantial reduction in transducfion when administered systemically, as demonstrated in preclinical studies in animal models and in human clinical trials. We have characterized the threshold titer of pre-existing NAb that is compromising to AAVS gene transfer in nonhuman primates. Pre-existing NAb fiters in excess of 1:10 substantially diminish hepatocyte transduction at the dose of 3x10^^ genonne copies/kg. Based on our survey in human samples, we predict that 25% of humans in the USA will not be suitable for systemic delivery of AAVS vector. Engineered vectors that can escape neutralization would provide a more general and effective solufion. In this project, we will employ mulfiple approaches guided by AAV structures with the ultimate aim to generate an "AAVS-prime" (AAVS') vector that retains the high liver tropism of AAVS and is more resistant to neutralization in humans.

Public Health Relevance

Many inherited metabolic diseases, such as OTC deficiency, are lacking effective treatments. Adeno- associated vector-mediated hepatic gene therapy has the potential to provide an alternative to cure or treat these life-threatening disorders. This project aims to developing improved vectors to overcome the barriers to achieving efficient therapeutic effects.

Agency
National Institute of Health (NIH)
Institute
Eunice Kennedy Shriver National Institute of Child Health & Human Development (NICHD)
Type
Research Program Projects (P01)
Project #
5P01HD057247-07
Application #
8652991
Study Section
Pediatrics Subcommittee (CHHD)
Project Start
Project End
Budget Start
2014-04-01
Budget End
2015-03-31
Support Year
7
Fiscal Year
2014
Total Cost
$203,519
Indirect Cost
$76,320
Name
University of Pennsylvania
Department
Type
DUNS #
042250712
City
Philadelphia
State
PA
Country
United States
Zip Code
19104
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Wang, Lili; Bell, Peter; Lin, Jianping et al. (2011) AAV8-mediated hepatic gene transfer in infant rhesus monkeys (Macaca mulatta). Mol Ther 19:2012-20
Bell, Peter; Wang, Lili; Gao, Guangping et al. (2011) Inverse zonation of hepatocyte transduction with AAV vectors between mice and non-human primates. Mol Genet Metab 104:395-403
Wang, Lili; Calcedo, Roberto; Bell, Peter et al. (2011) Impact of pre-existing immunity on gene transfer to nonhuman primate liver with adeno-associated virus 8 vectors. Hum Gene Ther 22:1389-401

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