766. Human Hematopoietic (CD34+) Stem Cells Possess High Affinity Receptors for Adenovirus Type 11p

Gene transfer into human hematopoietic stem cells using Ad5 has been shown to be inefficient due to lack of the primary receptor CAR and the secondary receptors avβ3 integrin and avβ5 integrin, and due to the high seroprevalence of Ad5 antibodies in most adults, resulting in diminished gene transduction. In the present study, we screened 6 species (species A-F) of adenovirus, displaying different tropisms for interaction with CD34+ cells, at the level of virus attachment and expression. Virus particles were biotinylated and their binding capacity was determined by FACS analysis using streptavidin-FITC. Ad11p, Ad35 and Ad3 (species B) showed high binding affinity, while Ad7, Ad11a (species B) and Ad37 (species D) displayed intermediate affinity. Virions of Ad4 (species E), Ad5 (species C), Ad31(species A) and Ad41(species F) hardly bound to hematopoietic progenitor cells. By using a double-labeling system, we demonstrated that adenoviruses did bind to quiescent CD34+ cells. Ad11p virions showed the highest affinity. We further confirmed that virus fiber-specific receptors were present on the hematopoietic progenitor cell surface, since both recombinant fiber of Ad11p and specific antiserum against rfiber could block virus attachment. The ability of Ad11p, Ad35 and Ad5 to infect hematopoietic cells was studied by immunofluorescence staining. Ad11p and Ad35 showed higher infectivity than Ad5. Thus, we have confirmed that these cells have high affinity receptors for species B:2 human adenoviruses Ad11p and Ad35, and these viruses may be used as candidate vectors to target therapeutic genes to hematopoietic stem cells.