Abstract: The present invention provides a modified cell having adhesion properties that are increased as compared to the adhesion properties of an unmodified cell, comprising a) a recombinant nucleic acid encoding an integrin ?3 subunit; b) a recombinant nucleic acid encoding an integrin ?v subunit; c) a recombinant nucleic acid encoding an integrin ?IIb subunit; and/or d) any combination of (a), (b) and (c).

Abstract: A retroviral delivery system capable of transducing a target site is described. The retroviral delivery system comprises a first nucleotide sequence coding for at least a part of an envelope protein; a second nucleotide sequence coding for at least a part of an envelope protein and one or more other nucleotide sequences derivable from a retrovirus that ensure transduction of the target site by the retroviral delivery system; wherein the first and second nucleotide sequences are heterologous with respect to at least one of the other nucleotide sequences; and wherein the first nucleotide sequence codes for at least a part of an influenza HA protein or a mutant, variant, derivative or fragment thereof that is capable of recognising the target site. Preferably said second protein is an influenza M2 protein.