Vector Specific Tolerance Induction for Airwary Gene Therapy

The success of adenoviral mediated airway gene therapy is hindered by host immune responses against adenoviral vectors. Helper-dependent adenoviral vectors (HD-Ad) are devoid of viral coding sequences and have an improved safety profile compared to earlier generation adenoviral vectors. However, intranasal delivery of HD-Ad vectors potentiates a pulmonary adaptive immune response, described in chapter 2, which is a barrier to gene therapy. One of the ways to reduce the immunogenicity of HD-Ad vectors is to increase the efficiency of HD-Ad mediated gene transfer to the airways, which would lessen the immunogen availability, limiting immune response against HD-Ad vectors. In chapter 3, a viral formulation strategy using Nacystelyn and DEAE-Dextran to substantially increase the efficacy of adenoviral mediated gene transfer to the airways is described. To further reduce the immune response to HD-Ad vectors, I have developed two novel strategies to induce vector-specific tolerance. The first strategy, described in chapter 4, involves the use of dendritic cells (DCs) differentiated in presence of IL-10, which are refractory to HD-Ad induced maturation and instead prime generation of regulatory T cells which suppress HD-Ad induced T cell proliferation. Delivery of these DCs pulsed with HD-Ad vectors to mice results in induction of immunological tolerance along with sustained gene expression following multiple rounds of HD-Ad readministrations. The second strategy, described in chapter 5, involves delivery of apoptotic DCs followed by delivery of antigen towards which tolerance needs to be generated. Apoptotic DCs are readily taken up by viable DCs, which suppresses DC maturation and induces TGF-β1 secretion, driving generation of regulatory T cells towards the delivered antigen. This strategy has shown remarkable success in achieving tolerance towards ovalbumin. Therefore, these strategies can be used to induce immunological tolerance towards gene therapy vectors which will likely allow for sustained and long term therapeutic transgene expression.Ph