Unveiling the sex bias: higher preexisting and neutralizing titers against AAV in females and implications for gene therapy.

Gene therapy with AAV vectors is a promising approach for treating numerous genetic disorders but is often hindered by preexisting antibodies that neutralize the vectors. Given that females may exhibit stronger immune responses than males, this study hypothesizes that females may have higher preexisting antibody titers against AAV. Serum samples from two U.S. cohorts were analyzed for antibody titers, antibody subtypes, and transduction inhibition activity against AAV serotypes AAV1, AAV2, AAV5, AAV8, and AAV9. We found that among seropositive samples, females had higher preexisting antibody levels and neutralizing activities against AAV9 and other serotypes. Immunoglobulin subclass analysis showed IgG1 dominance in both sexes, but females had higher IgA levels, whereas males had higher levels of IgG2. We further evaluated the cellular level of this differential immune response to AAV by stimulation of male and female human PBMCs. We observed dose-dependent increase in cytokines and chemokines in female PBMCs which suggests a differential inflammatory response. Altogether, our findings suggest that the enhanced immune response in females could lead to neutralization and faster clearance of AAV vectors with potential to impact the efficacy of gene therapy.