Adeno-associated virus (AAV) vectors are promising modalities of gene therapy to address unmet medical needs. However, anti-AAV neutralizing antibodies (Nabs) hamper the vector-mediated therapeutic effect. Therefore, the Nab prevalence in the target population is vital in designing clinical trials with AAV vectors. Hence, updating the seroprevalence of anti-AAV Nabs, herein we analyzed sera from 100 healthy individuals and 216 hemophiliacs in Japan. In both groups, the overall seroprevalence against various AAV serotypes was 20%-30%, and the ratio of Nab-positive population increased with age. The seroprevalence did not differ between healthy participants and hemophiliacs and was not biased by the concomitant blood-borne viral infections. The high neutralizing activity, which strongly eliminates the transduction with all serotypes, was mostly found in the 60s or older age. The multivariate analysis suggested that 60s or older age was the only independent factor related to the high titer of Nabs. Conversely, a large proportion of younger hemophiliacs was seronegative, rendering them eligible for AAV-mediated gene therapy in Japan. Compared with our previous study, the peak of seroprevalences has shifted to older populations, indicating natural AAV exposure in the elderly has occurred in their youth but not during the last decade.

The authors have declared no competing interest.

This study was funded by AMED [JP18pc0101030].

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The details of the IRB/oversight body that provided approval or exemption for the research described are given below:

The Institutional Review Board at Jichi Medical University gave ethical approval for this work (permission number: A19-108).

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All data produced in the present study are available upon reasonable request to the authors.