Abstract: This invention is directed to a soluble complex of ligands that binds to surface molecules of hemopoietic cells and result in their activation or expansion. The complex may be used in the activation and/or expansion of hemopoietic cells, optionally in combination with their transduction. The complex of ligands bind at least two cell surface molecules, such as one that plays a role in cell-cell adhesion and one that may or may not activate or stimulate the cell to promote growth and/or proliferation after binding to a ligand. A complex of ligands that bind two hemopoietic cell stimulatory molecules is also provided. The invention further provides for the use of the complex to target vectors to hemopoietic cells.

Abstract: The invention relates to a method of increasing vector transduction in target cells. The invention provides for the recombinant engineering of a packaging cell line to be capable of expressing one or more membrane proteins which facilitate binding to, and activation of, a target cell. The invention also provides for recombinant engineering of a cell that endogenously expresses one or more such membrane proteins into a packaging cell line. A vector packaged into viral particles via use of such cell lines would comprise an outer envelope containing these proteins. The particles would be specifically suited for binding and targeting to a target cell to facilitate transduction thereof with the vector. The target cell may also be simultaneously activated (stimulated) by the packaged vector in the absence of exogenously supplied stimulatory molecules.