A helper-independent adenovirus vector with E1, E3, and fiber deleted: Structure and infectivity of fiberless particles

The adenovirus (Ad) fiber protein largely determines viral tropism through interaction with specific cell surface receptors. This molecule may also be involved in virion assembly or maturation, as some previously characterize d fiber mutants were defective for processing of viral structural proteins. We previously described packaging cell lines that express Ad type 5 (Ad5) fiber and can complement the temperature-sensitive Ad fiber mutant H5ts142. We have now used these packaging cells to construct a new adenoviral vecto r (Ad5.beta gal.Delta F) with E1, E3, and L5 (fiber) deleted and analyzed t he fiber null phenotype. Ad5.beta gal.Delta F growth was completely helper independent, and fiberless particles were produced by a single final round of growth in 293 cells. Cryoelectron microscopic studies and sodium dodecyl sulfate-polyacrylamide gel electrophoresis analysis showed that the struct ure and composition of these particles was nearly identical to those of fir st-generation Ad vectors. As expected, fiberless particles had reduced infe ctivity on epithelial cells, but they retained the ability to infect monocy tic cells via an integrin-dependent pathway. These studies provide a novel approach to developing retargeted Ad gene therapy vectors.