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, rAAVRD and rAAVHD, were systemically compared. Results demonstrated that both rAAVRD and rAAVHD exhibited similar DNA packaging profiles, while rAAVHD capsids contained fewer VP1 and VP2 proteins, indicating that the rAAVHD particles contained a higher DNA/protein ratio than that of rAAVRD particles. Dynamic light scattering and transmission electron microscopy data revealed that the diameter of rAAVHD was smaller than that of rAAVRD. In vitro, rAAVHD was two- to fourfold less efficient in transduction compared with rAAVRD. However, the transduction performance of rAAVHD and rAAVRD was similar in vivo. No significant difference in neutralizing antibody formation against rAAVRD and rAAVHD was observed, suggesting that the surface epitopes of rAAVRD and rAAVHD are congruent. In summary, the results of this study demonstrate that rAAVRD and rAAVHD are equally competent for in vivo transduction, despite their difference in vitro. Therefore, the use of rAAVHD vectors in human gene therapy should be further evaluated.
Keywords: AAV; capsid; density; gene therapy.