376 An Adenovirus Serotype 5 Vector with Tat PTD Hexon Modification and Serotype 35 Fiber Shows Greatly Enhanced Transduction Capacity of Human Primary Cell Cultures Molecular Therapy Volume 20, Suppl[.]
ADENOVIRUS AND OTHER DNA VIRUS VECTORS: BIOLOGY AND VECTOR DESIGN with no chronic toxicity However, an acute toxic response with potentially lethal consequences prevents applications of these vectors in clinical trials Kupffer cells of the liver are known to be a major barrier to efficient hepatocyte transductions as they rapidly and avidly remove blood-borne vector particles Understanding the mechanisms of adenoviral uptake by Kupffer cells and other reticuloendothelial cells may allow the development of strategies aiming at overcoming this important barrier to hepatocyte transduction and to achieve preferential hepatocyte gene transfer with reduced acute toxic response In the present study, we show that HDAd vector particles co-localize both in vitro and in vivo with Scavenger receptor A (SRA) and treatment with anti-SR-A antibodies reduces HDAd uptake in the J774A.1 macrophage cell line Moreover, we show that HDAd particles bind to scavenger receptor expressed on endothelial cells I (SREC-I) in vitro and in vivo in both Kupffer cells and endothelial cells, as indicated by hepatic co-staining of fluorescent HDAd vector with SREC-I in CD31 (marker of endothelial cells) and CD68 (marker of Kupffer cells) positive cells In addition, we show that pre-treatment of mice with blocking antibodies against SR-A and SREC-I significantly increases hepatocyte transduction efficiency In contrast with prior studies indicating the main adenovirus scavenger to be the Kupffer cell, recent work has drawn attention to liver sinusoidal endothelial cells as the primary cells involved in adenovirus clearance Here, we have identified SREC-I as a receptor involved in HDAd vector binding and uptake by endothelial cells of the liver In summary, we have shown that SR-A and SREC-I are both involved in HDAd vector uptake and are potential targets to improve the vector therapeutic index by reducing reticuloendothelial uptake which may allow the use of lower, less toxic doses 375 Incorporation of Pseudomonas aeruginosa Epitope in Novel Adenovirus Fiber Loops To Circumvent Anti-Adenovirus Immunity and To Induce Protective Immunity Anurag Sharma,1 Anja Krause,1 Biin Sung,1 WenZhu Wu,1 Stefan Worgall.1 Genetic Medicine, Weill Medical College of Cornell University, New York, NY Expression of pathogen-derived antigenic epitopes on the adenoviral (Ad) capsid proteins is a useful strategy for the induction of anti-pathogen immunity We have previously shown that Ad vector with epitope on its fiber elicited the strongest anti-epitope immune response as compared to when same epitope is incorporated in hexon, penton or protein IX To further explore the alternate locations within the Ad fiber protein and in order to enhance the epitope-specific immune response by capsid-modified Ad vectors, we generated several fiber-modified Ad vectors incorporating Pseudomonas aeruginosa immune-dominant OprF epitope (Epi8) into loops CD (AdZ.F(CD)Epi8), DE (AdZ.F(DE)Epi8), FG (AdZ.F(FG)Epi8), HI (AdZ.F(HI)Epi8) or IJ (AdZ.F(IJ)Epi8) of fiber protein and HVR5 loop (AdZ.HexEpi8) of hexon protein, and induction of anti-epitope immune response by these viruses was investigated and compared with Ad expressing full-length OprF (Ad-OprF) To evaluate the immunogenicity of these fiber-modified vectors, Balb/c mice were immunized intramuscularly with 1010 particle units of each vector and the serum anti-Ad and anti-OprF IgG antibodies were analyzed by ELISA While equivalent titers of anti-Ad antibody were observed in all the groups after weeks (P>0.05), marked differences were observed in anti-OprF titers Immunization with AdZ.F(FG)Epi8 and AdZ.F(HI)Epi8 elicited higher anti-OprF titers compared to AdZ.F(CD)Epi8, AdZ.F(DE)Epi8, AdZ.F(IJ)Epi8 or AdZ.HexEpi8 (P