cells amplified the rep gene gt 100 fold after ad5 infection while ad5 induced only a 3 fold rep gene amplification in c2 vero cells these experiments indicated that ad5 helper functions could be improved for example by use of the rad5 e3 tre rep52 40 described herein in addition one group i simian adenovirus sv 20 when substituted for the human ad5 helper virus in the vero cell production system described above was found to increase raav egfp yield 24 fold c2 vero and 2f10 hela raav2 egfp producer cells were infected over a range of moi 1 10 100 with ad5 or one of four simian ad sv 15 atcc vr 1449 sv 20 atcc vr 199 sv 27 atcc vr 202 or sv 32 vr 205 forty eight hours after infection cells were collected heat inactivated at 56 u00b0 c and subjected to 3 freeze thaw cycles to release raav egfp clarified lysate dilutions were prepared and used to infect c12 cells aav2 rep expressing cell line and green fluorescent cells gfu were counted at 36 hours post infection results are presented in fig6 analysis of aav2 rep gene amplification in the c12 cells infected data not shown was consistent with the increased yield observed showing 10 fold rep gene amplification with ad5 infection 65 fold amplification with sv 15 infection or 145 fold amplification.