Effect of human vitreous humour components and neutralising antibodies on transduction activity of recombinant AAV2, AAV5, AAV6 and AAV8

Intravitreal injection of recombinant adeno-associated virus (AAV) might be an alternative approach for retinal gene therapy for certain applications. Although the jelly-like substance consists mainly of water, anti-viral antibodies against various viruses such as HIV or HSV have been observed in the human vitreous and anti-AAV neutralising antibodies (NAbs) in rhesus macaque vitreous have also been detected. In this study, the human vitreous humour was obtained from 70 post mortem unpaired eye cups and 10 paired eye cups from the Queensland Eye Bank. The transduction efficiency of 1-3 · 108 vcg of recombinant AAV-2, -5, -6 and -8 expressing secreted nanoluciferase was measured following transduction of ARPE-19 and Cos-7 cells at vitreous humour dilutions from 1:2 to 1:10 000. At vitreous humour dilution of 1:2, a reduction in transduction of over 50% was observed for AAV2 in 50.5% of samples and for AAV6 in 66.2% of samples. Only 23.2% of tested samples showed similar reduction in transduction efficiency for AAV5, and for AAV8 only 2.5% of samples inhibited transduction by 50% at 1:2 dilution. Differences in serum antibody levels have been previously observed in a similar Australian population, but low transduction inhibition at vitreous humour dilutions of 1:100 suggests that the concentration of NAbs within the vitreous humour is lower than in human serum. In addition, this study also reported an increase in transduction efficiency for AAV8 at highest vitreous humour concentrations, supporting previous reports that human albumin can increase AAV transduction but only in some serotypes.