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Updated: Feb 6, 2026
Adeno-associated Virus-mediated Transgene Expression in Genetically Defined Neurons of the Spinal Cord
Published on: May 12, 2018
Dosage Thresholds and Influence of Transgene Cassette in Adeno-Associated Virus-Related Toxicity
Hanen Khabou1, Chloé Cordeau1, Laure Pacot1
11 Sorbonne Universités, UPMC Univ Paris 06, INSERM, CNRS, Institut de la Vision , Paris, France; and Inserm UMR_S951, Univ Evry, Université Paris-Saclay, EPHE, Evry, France.
Abstract:
Today, there are >500 published studies and 40 clinical trials to treat retinal disorders using gene therapy. The great majority of them rely on the use of adeno-associated virus vectors (AAV) for therapeutic gene delivery. Thus far, AAVs have an excellent safety profile in the clinic. Nevertheless, it is known that AAV-mediated gene delivery leads to toxicity at higher input doses in experimental gene therapy. This study reveals the factors that contribute to retinal toxicity after subretinal administration of AAV vectors in wild-type mice. The study shows that alongside the input dose, the nature of the transgene and the cells mediating the expression determine the extent of toxicity. Importantly, the study shows that AAV vectors encoding green fluorescent protein (GFP) used as controls in experimental gene therapy are toxic at doses as low as 5 × 109 vg, confounding the observed therapeutic effect in gene therapy paradigms. Altogether, the data show the importance of reducing input doses while increasing transgene expression levels via the use of more efficient capsids and promoters in order to avoid side effects in AAV-mediated gene therapy. Furthermore, the toxicity observed with AAV-GFP vectors imply a reinterpretation of previous gene therapy studies where the therapeutic effect was measured in relation to this control.
Insights
Adeno-associated virus (AAV) gene therapy for retinal disorders can cause toxicity. Dose, transgene, and cell type influence this toxicity, with AAV-GFP controls being unexpectedly harmful.
Area of Science:
- Ophthalmology
- Gene Therapy
- Molecular Biology
Background:
- Gene therapy, particularly using adeno-associated virus (AAV) vectors, is a promising approach for treating retinal disorders, with over 500 studies and 40 clinical trials.
- While AAV vectors generally exhibit a good safety profile in clinical settings, preclinical studies indicate potential toxicity at higher doses.
- Understanding the factors contributing to AAV-mediated retinal toxicity is crucial for optimizing gene therapy strategies and ensuring patient safety.
Purpose of the Study:
- To investigate the factors influencing retinal toxicity following subretinal administration of AAV vectors in wild-type mice.
- To determine the impact of transgene type and expressing cells on AAV-induced retinal toxicity.
- To evaluate the toxicity of AAV vectors encoding green fluorescent protein (GFP), commonly used as a control in gene therapy experiments.
Main Methods:
- Subretinal administration of various AAV vectors in wild-type mice.
- Assessment of retinal toxicity in relation to AAV input dose, transgene, and cell type mediating expression.
- Specific evaluation of AAV-GFP vector toxicity at doses relevant to experimental gene therapy controls.
Main Results:
- Retinal toxicity is dependent on multiple factors, including AAV input dose, the specific transgene delivered, and the cell types expressing the transgene.
- AAV vectors encoding GFP, frequently used as controls, demonstrated significant toxicity at doses as low as 5 × 10^9 vg.
- This toxicity associated with AAV-GFP controls can confound the interpretation of therapeutic effects in gene therapy studies.
Conclusions:
- Minimizing AAV input doses is essential for mitigating retinal toxicity in gene therapy.
- Enhancing transgene expression levels through more efficient capsids and promoters can help reduce the required AAV input dose, thereby minimizing side effects.
- The observed toxicity of AAV-GFP vectors necessitates a re-evaluation of previous gene therapy studies that used these vectors as controls.
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