The objectives of this research are to develop and characterize novel adenovirus vectors for gene therapy of cystic fibrosis. Vectors will be constructed using both existing technology and approaches to be developed. All vectors will have replacements of early region I (E1) of the viral genome with foreign DNA encoding either reporter genes or the cystic fibrosis transmembrane -conductance regulator (CFTR). To maximize the capacity of the vectors early region 3 will also be deleted. Deletion of El removes the viral sequences involved in cell transformation and results in replication defective vectors. To further reduce the potential four complications during therapy due to cytopathic effects, additional attenuating mutations (besides deletion of E1) will be introduced into vectors and the effects of the mutations on ability of the vectors to cause cell killing and induce in vivo pathology will be determined. On the assumption that preexisting immunity or immunity induced by repeated treatment with transducing viruses may limit their effectiveness in gene therapy, vectors derived from additional human serotypes and from one nonhuman (bovine) adenovirus will be developed. The possibility that bovine adenovirus vectors may have reduced cytopathic effect in human cells and reduced pathogenicity will be examined. Finally, to explore ways of establishing foreign genes as permanently maintained elements in transduced cells, systems will be designed based on the Epstein-Barr Virus plasmid DNA replication components to permit episomal replication of genes transduced into primate and canine cells by adenovirus vectors. In another approach the bacteriophage PI Cre/lox site specific recombinase system will be used to enhance integration of transduced genes into cellular DNA. Persistence and structure of transferred DNA and duration and levels of gene expression will be examined.
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