TRANSDUCTION WITH RECOMBINANT ADENOASSOCIATED VIRUS FOR GENE-THERAPY IS LIMITED BY LEADING-STRAND SYNTHESIS

Adeno-associated virus is an integrating DNA parvovirus with the poten tial to be an important vehicle for somatic gene therapy. A potential barrier, however, is the low transduction efficiencies of recombinant adeno-associated virus (rAAV) vectors. We show in this report that ade novirus dramatically enhances rAAV transduction in vitro in a way that is dependent on expression of early region 1 and 4 (E1 and E4, respec tively) genes and directly proportional to the appearance of double-st randed replicative forms of the rAAV genome, Expression of the open re ading frame 6 protein from E4 in the absence of El accomplished a simi lar but attenuated effect, The helper activity of adenovirus El and E4 for rAAV gene transfer was similarly demonstrated in vivo by using mu rine models of liver- and lung-directed gene therapy. Our data indicat e that conversion of a single-stranded rAAV genome to a duplex interme diate limits transduction and usefulness for gene therapy.