Abstract 3982: Improved Safety Profile of Novel Adenovirus Based Vectors “Capsid-displaying” Complement Inhibitors: Increased Potential for Cardiovascular Gene Transfer Applications
Adenovirus (Ad) based vectors continue to be the most commonly utilized vector for gene therapy trials, with cardiovascular diseases being a primary target. Despite this, Ad induced innate immune responses limit enthusiasm towards more widespread utilization of Ad vectors. Many of these innate immune responses are initiated by Ad capsid activation of the complement system. In this study we characterized a new class of Ad vector, genetically engineered to “capsid-display” the natural complement inhibitor decay accelerating factor (DAF), in an effort to mitigate/abrogate complement dependent innate immune responses. We found that several dosages of an Ad5-GFP control virus caused acute thrombocytopenia. In contrast, the Ad vector displaying DAF did not induce thrombocytopenia. In fact, platelet counts in Ad5-dDAF injected WT mice were not significantly different from counts obtained from Ad5-GFP injected complement deficient (C3-KO) mice at any time point or dose tested. Next, utilizing quantitative bead array based assays we determined that intravenous injection of Ad5 vectors induce release of sICAM-1 (1.5 fold) and sE-selectin (6 fold). In contrast, Ad5-dDAF injected mice had sICAM-1 and sE-selectin plasma levels identical to those measured in Ad5-GFP injected C3-KO mice, and significantly reduced as compared to Ad5-GFP injected WT mice. Ad5-GFP injected C3-KO mice, as well as WT mice injected with the Ad5-dDAF vector had significantly reduced activation of pro-inflammatory genes in heart tissues as compared to WT mice treated with a conventional Ad vector. We found that Ad5-dDAF induction of TLR9, MyD88 and NFkB was significantly mitigated, indicating reduced inflammation in the heart.
Conclusion: We have developed a viable, highly improved Adenovirus vector that capsid displays the human DAF complement regulator. This novel vector significantly reduced Ad triggered thrombocytopenia, endothelial cells activation and pro-inflammatory gene induction in heart tissues, while preserving transduction efficiency. We believe that DAF displaying Ad vectors may become an important gene transfer platform for a variety of cardiovascular applications.
This research has received full or partial funding support from the American Heart Association, Midwest Affiliate (Illinois, Indiana, Iowa, Kansas, Michigan, Minnesota, Missouri, Nebraska, North Dakota, South Dakota & Wisconsin).