High-Density Recombinant Adeno-Associated Viral Particles are Competent Vectors for In Vivo Transduction

Recombinant adeno-associated viral (rAAV) vectors have recently achieved clinical successes in human gene therapy. However, the commonly observed, heavier particles found in rAAV preparations have traditionally been ignored due to their reported low in vitro transduction efficiency. In this study, the biological properties of regular and high-density rAAV serotype 8 vectors, rAAV RD and rAAV HD , were systemically compared. Results demonstrated that both rAAV RD and rAAV HD exhibited similar DNA packaging profiles, while rAAV HD capsids contained fewer VP1 and VP2 proteins, indicating that the rAAV HD particles contained a higher DNA/protein ratio than that of rAAV RD particles. Dynamic light scattering and transmission electron microscopy data revealed that the diameter of rAAV HD was smaller than that of rAAV RD . In vitro , rAAV HD was two- to fourfold less efficient in transduction compared with rAAV RD . However, the transduction performance of rAAV HD and rAAV RD was similar in vivo . No significant difference in neutralizing antibody formation against rAAV RD and rAAV HD was observed, suggesting that the surface epitopes of rAAV RD and rAAV HD are congruent. In summary, the results of this study demonstrate that rAAV RD and rAAV HD are equally competent for in vivo transduction, despite their difference in vitro . Therefore, the use of rAAV HD vectors in human gene therapy should be further evaluated.