Characterization of Immune Responses to rAAVrh8 Gene Therapy for GM2 Gangliosidosis in Phase 1/2 Trial

Abstract Understanding how the immune system responds to adreno-associated virus (AAV) gene therapy and potentially modulating that response is vital to their safety and ultimate success. However, the immune response in the central nervous system (CNS) to AAV gene therapy is still not well understood. Here, we characterized the immune responses to AAVrh8 vectors injected into the thalamus and cerebral spinal fluid (CSF) of Tay-Sachs (TSD) and Sandhoff (SD) disease patients. Nine patients in four dose cohorts were treated with gene therapy while being immunosuppressed with rituximab, sirolimus and prednisolone. Neutralizing antibodies against AAV capsid were detected in the serum of 9/9 patients and in the CSF of 7/9 patients. Specific T-cell responses against the AAV capsid were documented in all patients, with most patients developing responses at 2–3 weeks post-injection. Flow cytometry suggested the induction of capsid-specific regulatory T-cells in the periphery. Local immune responses were detected by cytokine analysis of the CSF along with upregulation of several chemokines, including CXCL8, CXCL9 and CXCL10. These Phase I/II clinical trial data provide valuable insights into how the human immune system responds to direct administration of AAV into the CNS and important assessments on the efficacy of the immune suppression regimen which can be used to inform future AAV clinical trials. Competing Interest Statement The authors have declared no competing interest. Clinical Trial NCT04669535; NCT06614569; IND#19314 Funding Statement This study did not receive any funding. Author Declarations I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained. Yes The details of the IRB/oversight body that provided approval or exemption for the research described are given below: Ethical oversight of this study was provided by Western Institutional Review Board (Western IRB). The vector is being studied under Investigational New Drug (IND) #19314. All versions of the study as amended were approved by the Institutional Biosafety Committee of UMass Chan Medical School, WCG IRB, and Massachusetts General Hospital IRB. All patients were enrolled into this study after informed consent was obtained from their parents/guardians. These trials are registered on clinicaltrials.gov under identifiers NCT04669535 and NCT06614569. I confirm that all necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived, and that any patient/participant/sample identifiers included were not known to anyone (e.g., hospital staff, patients or participants themselves) outside the research group so cannot be used to identify individuals. Yes I understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as ClinicalTrials.gov. I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance). Yes I have followed all appropriate research reporting guidelines, such as any relevant EQUATOR Network research reporting checklist(s) and other pertinent material, if applicable. Yes Data Availability All data produced in the present study are available upon reasonable request to the authors.