Anti-Adeno-Associated virus (AAV) neutralizing antibody (Nab) titers in Duchenne muscular dystrophy (DMD)

Objective: To study the prevalence of anti-AAV types 2 and 9 Nab titers in the DMD cohort. Background: Gene therapy using AAV vectors in DMD. Design/Methods: Prospective study of 89 DMD boys (median age 10.5 years, range 2–20 years, 58.4% ambulatory, 55% on steroids) from 2016 to 2020. AAV2/9 neutralization assays were performed for each patient. Briefly, patient serum was serially diluted in media, combined with CMV-luciferase reporter contstruct containing AAV2/9 viral particles, and incubated for 1 hour. HeLa cells were pre-infected with Adenovirus-5. After incubation, the antibody-AAV mixtures were aliquoted onto the Adenovirus-5-infected HeLa cells and incubated for 2 days. To calculate AAV2/9 infection, plates were washed, luciferase substrate was added, and read on a luminometer. AAV2/9 neutralizing titers are reported as the estimated dilution at which 50% of AAV2/9 infection has been inhibited (IC50). Descriptive statistics were used for data analysis. The Institutional Review Board (#87515) approved study. Results: Anti-AAV 2 and 9 Nab were found in 51% (n=45) and 39% (n=35) DMD boys. Thirty nine percent (n=35) has both anti-AAV 2 and 9 Nab. Nab positive subjects were stratified based upon age 12 years and steroid use (tables 1, 2). Ages 5–12 years had the highest prevalence of anti-AAV2 and 9 Nab titers (57.8 and 60%) at high (>1:240) and moderate (1:20–1:240) dilution. Steroids versus no steroids use showed no difference in anti-AAV Nab status. Conclusions: We show significant rate of anti-AAV 2 and 9 Nab in our DMD population irrespective of steroid use. Lower rate of anti-AAV9 compared to anti-AAV2 Nab was seen and similar to the French DMD cohort (Leborgne et al, 2019). Ages 5–12 were highest positive group and likely secondary to school and daycare exposure. We anticipate this data will lead to clinical trial preparedness for gene therapy in near future. Disclosure: Dr. Verma has nothing to disclose. Raj Razdan has nothing to disclose. Dr. Upadhyayula has nothing to disclose. Dr. Phan has received personal compensation in the range of $500-$4,999 for serving on a Scientific Advisory or Data Safety Monitoring board for Wave Biosciences. Dr. Phan has received personal compensation in the range of $500-$4,999 for serving on a Scientific Advisory or Data Safety Monitoring board for Stealth. David Lee has nothing to disclose.