Seroprevalence of AAV neutralizing antibodies in males with Duchenne muscular dystrophy

Adeno-associated virus (AAV) based gene therapies are emerging strategies in Duchenne muscular dystrophy (DMD) treatment. Exposure to wild-type AAV can lead to development of neutralizing antibodies (NAb) and block AAV transduction, thereby limiting the delivery of AAV vector-based gene therapy. Therefore, it is imperative to check for the presence of AAV NAbs in a patient who is a candidate for gene therapy. We prospectively enrolled 101 genetically confirmed males with DMD (median age 11 years, 48% ambulatory, 59% on steroids) and performed AAV neutralization assays against AAV2, AAV8, AAV9, and AAVrh74 serotypes. Serotype analysis showed AAV9 (36%) and AAVrh74 (32%) seroprevalence was lower compared to AAV2 (56%) and AAV8 (47%). Interestingly, age was not correlated with NAb titer for any of the capsids. NAb responses were observed at a higher frequency in African American participants and at a lower frequency for Caucasian participants for all four serotypes. Further analysis showed no significant differences in NAb titers depending, regardless of serotype, on whether participants were taking steroids. Finally, we observed higher AAV8, AAV9, and AAVrh74 seroprevalence and significantly higher AAV2 and AAV8 NAb titers in participants that were ambulatory compared to the non-ambulatory participants. Overall, these data identify AAV9 and AAVrh74 as the two serotypes with lower preexisting NAbs in this study's cohort of 101 males with DMD, possibly showing their utility for future gene therapy applications to treat this cohort men with DMD.