This study aims to assess the overall seroprevalence of neutralizing antibodies against different AAVs potentially used in gene therapy in patients with genetic neuromuscular diseases.

This research aims to determine the seroprevalence and immunological profiles of recent and/or emerging AAV capsids that could be used in future gene therapy programs. It will thus make it possible to: 1/ improve knowledge of the prevalence of anti-AAV antibodies (total and neutralizing) in these specific populations; 2/ identify the clinical, demographic or biological factors likely to influence this seroprevalence (age, sex, type of pathology, immunosuppressive treatment followed); 3/ to characterize the phenomena of cross-reactivity between different serotypes or variants of capsids, a major challenge for the design of new generations of vectors.

The data generated will contribute to a better estimation of the populations potentially eligible for gene therapies, by making it possible to anticipate exclusion rates related to pre-existing immunity. They may also guide the rational selection of alternative capsids that are less immunogenic or evade cross-immunity, as well as the development of immunomodulation or re-assay strategies.

Inclusion Criteria:

1. Pediatric patient 6 years of age or older or adult under 60 years of age with genetic neuromuscular disease
2. Informed patient who signed informed consent
3. No opposition from the holders of parental authority or guardian, for minor patients.
4. Affiliated/beneficiary of a national health insurance scheme

Exclusion Criteria:

• Gene or cell therapy treatment prior to blood collection

Individual participant data (IPD) will not be shared due to the sensitive nature of the data and the need to protect patient confidentiality, in accordance with applicable data protection regulations.