Increased gene transfer in acute myeloid leukemic cells by an adenovirus vector containing a modified fiber protein

Applications of gene transfer in acute myeloid leukemia (AML) blast cells h ave still not been developed, mostly due to the lack of an efficient vector Adenoviruses have many advantages as vectors, but remain poorly efficient in cells lacking fiber receptors. A promising strategy is the retargeting o f adenoviruses to other cellular receptors. We report the dramatic enhancem ent of gene transfer efficiency in AML blasts using AdZ.F(pK7), a modified adenovirus containing a heparin/heparan sulfate binding domain incorporated into the fiber protein of the adenovirus. We transduced 25 AML blast sampl es with efficiency reaching 100% of the cells in most samples. Optimal resu lts were obtained at 8400 physical particles per cell, corresponding to a m ultiplicity of infection of 100 plaque forming units per cell. Control AdZ. F adenovirus efficiently transduced leukemic cell lines but gave poor resul ts in AML samples. Both addition of soluble heparin and cell treatment with heparinase inhibited AdZ.F(pK7) gene transfer showing that heparan sulfate s are the major receptors mediating AdZ.F(pK7) transduction of AML blasts. Although adenoviruses can infect nondividing cells, we observed that a comb ination of growth factors (GMCSF, IL-3, stem cell factor) was required for efficient transduction in order to maintain AML blast cell viability. This study demonstrates that retargeting the adenovirus fiber protein to heparan sulfates can overcome the low efficiency of adenovirus in AML blast cells and may provide a useful tool for gene therapy approaches in AML.