Intracellular trafficking of a fiber-modified adenovirus using lipid raft/caveolae endocytosis.

Most adenoviral vectors (HAdvs) elaborated for gene therapy are derived from serotype 5 viruses that use clathrin-coated vesicle endocytosis for cell entry. However, it appears that adenoviral vectors are able to take advantage of lipid raft/caveolae endocytosis to infect cells. In vivo targeting of a therapeutic gene to specific cells by vector engineering has become a major focus of gene therapy research. Yet, modification of adenoviral tropism, especially fiber gene engineering, can induce deficient intracellular trafficking of the viral particle, with a shift in subcellular localization resulting in extensive exocytosis. In this study we demonstrate that uptake of a fiber-modified adenovirus using lipid raft/caveolae endocytosis leads to non-altered intracellular trafficking without endosomal retention. Moreover, activation of lipid raft structures by this vector leads to the formation of "mega-caveosomes". These results demonstrate that, by forcing adenoviruses to take advantage of a non-clathrin, non-classical endocytic pathway, it is possible to compensate for the deficiency in endosomolysis that is associated with the use of some of the fiber-modified adenoviral constructs. Moreover, it renders such vectors ideal candidates for infecting human coxsackie and adenoviruses receptor (hCAR) negative cells.

A rapid and easy method for production and selection of recombinant adenovirus genomes.

Adenoviruses are used widely as vectors for gene therapy. Due to the large size of their genome there is a low frequency of unique restriction sites and many techniques have been described to construct recombinant viruses. Whatever the considered technique, the Escherichia coli strain BJ5183 is used to obtain recombinant adenovirus genomes in a plasmid, or to construct defective viral backbones which will be used to produce infectious viral particles by homologous recombination in HEK293 cells. Unfortunately BJ5183 bacteria do not produce a sufficient amount of plasmid DNA to allow for restriction analysis. Plasmids have to be transferred into another strain to detect the expected construction. It is reported now that the common E. coli strain, Top10F' can be used for the construction of recombinant adenovirus genomes. A plasmid carrying a kanamycin resistance gene and containing the two ends of the adenovirus genome was used. It permits modification by classical molecular biology techniques or homologous recombination at both ends of the genome. The remainder of the genome is introduced by homologous recombination in Top10F'. Several homologous recombination steps were successfully performed without the steps of extraction and introduction of plasmid DNA in another strain to check the plasmids obtained.