Prevalence of adeno-associated virus type 3B neutralizing antibodies in cohorts of healthy donors and Wilson's disease adults.

Adeno-associated virus (AAV) is widely used for liver-directed gene therapy, with AAV serotype 3B (AAV3B) showing particularly high tropism for human hepatocytes. However, pre-existing neutralizing antibodies (NAbs) against AAV represent a major barrier to efficient gene transfer and patient eligibility. We have recently demonstrated that subjects with intermediate NAb levels (1:5-1:45), that would be excluded from clinical trials, can be converted in eligible patients by the administration of IgG-cleaving enzymes. It is thus crucial to assess not only the seroprevalence but also titer distribution. Here, we analyzed anti-AAV3B NAb titers, using a validated cell-based transduction inhibition assay, in healthy adults and patients with Wilson's disease, a hepatic metabolic disorder amenable to AAV3B-mediated gene therapy. Two independent cohorts of healthy adults (n = 200 and n = 580) were analyzed; 33-36% of individuals were NAb positive, and prevalence increased with age. Differences were observed across ethnicities. Importantly, a substantial proportion of seropositive individuals (19%) exhibited intermediate NAb titers. In contrast, only 17.4% of Wilson's disease patients (n = 23) were positive, all with high NAb titers. These findings provide insights into target population eligibility, and titer distribution data support the potential of NAb-reduction approaches to expand access to systemic AAV3B-based gene therapies.