RetroNectin reagent is a 63-kD fragment of recombinant human fibronectin fragment (also referred to as rFN-CH-296) that enhances the efficiency of lentiviral- and retroviral-mediated gene transduction. This is particularly important for hematopoietic cells and other hard-to-transfect cell types. When coated on the surface of containers such as culture dishes, petri dishes, flasks or bags, RetroNectin significantly enhances virus-mediated gene transduction into mammalian cells. This enhanced transduction is thought to result from the colocalization of virus particles and target cells on the molecules of RetroNectin. Viral particles bind RetroNectin via interaction with heparin-binding domain II, and target cells bind mainly through the interaction of the cell surface integrin receptor VLA-4 with the fibronectin CS1 site.