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Published on: August 10, 2018
AAV5-miHTT gene therapy demonstrates suppression of mutant huntingtin aggregation and neuronal dysfunction in a rat
J Miniarikova1,2, V Zimmer3,4, R Martier1,2
1Department of Research & Development, uniQure N.V., Amsterdam, The Netherlands.
Insights
Gene therapy using adeno-associated viral vectors (AAV5) effectively lowered huntingtin (HTT) gene expression in a rat model of Huntington's disease (HD), preventing neuronal dysfunction and aggregate formation without immune response.
Area of Science:
- Neuroscience
- Genetics
- Molecular Biology
- Gene Therapy
Background:
- Huntington's disease (HD) is a fatal, progressive neurodegenerative disorder caused by a mutation in the huntingtin (HTT) gene.
- Currently, no treatments exist to halt or reverse HD progression.
- Lowering HTT expression, particularly the mutant form, is a promising therapeutic strategy.
Purpose of the Study:
- To evaluate the efficacy and gene specificity of engineered micro (mi)RNAs delivered via adeno-associated viral serotype 5 (AAV5) vectors for knocking down HTT in an acute HD rat model.
- To assess the safety and immune response associated with AAV5-delivered miRNA therapy.
Main Methods:
- Utilized engineered miRNA constructs (miHTT, miSNP50T) delivered by AAV5 vectors in an acute rat model of Huntington's disease.
- Assessed suppression of mutant HTT messenger RNA (mRNA) and aggregate formation.
- Monitored neuronal function (DARPP-32) and neuroinflammation markers (microglia, astrocytes).
Main Results:
- AAV5-miHTT and AAV5-miSNP50T constructs significantly suppressed mutant HTT mRNA levels.
- Suppression of mutant HTT prevented aggregate formation and rescued DARPP-32-associated neuronal dysfunction.
- No activation of microglia or astrocytes was observed, indicating no significant immune response to the AAV5 vector or miRNA sequences.
Conclusions:
- Adeno-associated viral vector-delivered miRNA-mediated HTT lowering demonstrates significant therapeutic potential for Huntington's disease.
- The AAV5-miSNP50T construct showed allele-selective HTT knockdown without passenger strand expression.
- The gene therapy approach showed no safety concerns related to immune activation, supporting further development for HD treatment.
Abstract:
Huntington's disease (HD) is a fatal progressive neurodegenerative disorder caused by a mutation in the huntingtin (HTT) gene. To date, there is no treatment to halt or reverse the course of HD. Lowering of either total or only the mutant HTT expression is expected to have therapeutic benefit. This can be achieved by engineered micro (mi)RNAs targeting HTT transcripts and delivered by an adeno-associated viral (AAV) vector. We have previously showed a miHTT construct to induce total HTT knock-down in Hu128/21 HD mice, while miSNP50T and miSNP67T constructs induced allele-selective HTT knock-down in vitro. In the current preclinical study, the mechanistic efficacy and gene specificity of these selected constructs delivered by an AAV serotype 5 (AAV5) vector was addressed using an acute HD rat model. Our data demonstrated suppression of mutant HTT messenger RNA, which almost completely prevented mutant HTT aggregate formation, and ultimately resulted in suppression of DARPP-32-associated neuronal dysfunction. The AAV5-miHTT construct was found to be the most efficient, although AAV5-miSNP50T demonstrated the anticipated mutant HTT allele selectivity and no passenger strand expression. Ultimately, AAV5-delivered-miRNA-mediated HTT lowering did not cause activation of microglia or astrocytes suggesting no immune response to the AAV5 vector or therapeutic precursor sequences. These preclinical results suggest that using gene therapy to knock-down HTT may provide important therapeutic benefit for HD patients and raised no safety concerns, which supports our ongoing efforts for the development of an RNA interference-based gene therapy product for HD.
