(298g) Development of an Adenovirus Gene Therapy Vector with Improved Transduction Efficacy and Reduced Innate and Adaptive Immune Response

Adenoviruses-based vectors, which are currently used in more than 25 % of ongoing gene therapy clinical trials, are a promising and relatively safe class of gene therapy vectors. Adenovirus, however, has limitations that hinder its use. For example, adenovirus may initiate an innate inflammatory immune response or may be cleared rapidly in patients with preexisting immunity. Even in patients without preexisting immunity, the adaptive immune response greatly limits repeat administration of the virus.  In addition, the dependency of the virus on the coxsackie-adenovirus receptor (CAR) compromises the ability of the virus to deliver genes to CAR-negative cells.

We developed a nanoparticle complex composed of adenovirus and a cell penetrating peptide (CPP)/polyethylene glycol (PEG) conjugate to reduce these drawback and produce an improved hybrid vector. The CPPs were used to enable the virus to transform cells independent of CAR, and PEG was used to prevent immune recognition, thereby reducing the innate and adaptive immune responses. The immune response towards the complexes and transduction efficiencies of the particles were optimized by varying the type of CPP (e.g., Tat, Penetratin, polyarginine and Pep1), degree of PEGylation, PEG molecular weight, and ratio of CPPs to adenovirus. In this study we found that CPP-PEG-Ad showed a 90-fold enhancement in gene transduction compared to the unmodified adenovirus when used to transduce CAR-negative cells. Moreover, the complexes were able to evade neutralizing antibodies and retained 90 % of their activity. Further, the complexes reduced the amount of proinflammatory cytokine (IL-6) produced by mouse macrophage cells. The results of the study demonstrate that modification of adenovirus with PEG and CPP can reduce immunogenic limitations associated with the virus while promoting transduction of cells not normally infected by adenovirus.