Adeno-associated viruses (AAVs) are promising gene therapy vectors, but challenges arise when treating patients with preexisting neutralizing antibodies. Worldwide seroprevalence studies provide snapshots of existing immunity in diverse populations. Owing to the uniqueness of the Basque socio-geographical landscape, we investigated the seroprevalence of eight AAV serotypes in residents of the Basque Country. We found the highest seroprevalence of AAV3, and the lowest seroprevalence of AAV9. Additionally, less than 50% of the Basque population has neutralizing antibodies against AAV4, AAV6, and AAV9. Our findings provide insight into AAV infections in the Basque region, public health, and the development of AAV-based therapeutics.

Basque Foundation for Science IKERBASQUE 48009 Bilbao Spain

Central European Institute of Technology Masaryk University Brno Czech Republic

Centro de Investigación Biomédica en Red de Enfermedades Hepáticas y Digestivas Instituto de Salud Carlos 3 Madrid Spain

Integrative Genomics Lab CIC bioGUNE BRTA Bizkaia Technology Park Derio Basque Country Spain

Precision Medicine and Metabolism Laboratory CIC bioGUNE BRTA Bizkaia Technology Park 48160 Derio Spain

Research and Development CIC bioGUNE BRTA Bizkaia Technology Park Building 801A 48160 Derio Spain

Structure and Cell Biology of Viruses Lab Center for Cooperative Research in Biosciences Bizkaia Technology Park 48160 Derio Spain

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