Keywords: Adeno-associated virus Capsid variants Induced human neurons Transduction efficiency Neuronal function

Background: Recombinant adeno-associated virus (AAV) is the most widely used vector for gene therapy in clinical trials. To increase transduction efficiency and specificity, novel engineered AAV variants with modified capsid sequences are evaluated in human cell cultures and non-human primates. Methods: We tested two novel AAV capsid variants, AAV2-NNPTPSR and AAV9-NVVRSSS, in human cortical neurons, which were directly converted from human induced pluripotent stem cells and cocultured with rat primary astrocytes. Results: AAV2-NNPTPSR variant efficiently transduced both induced human cortical glutamatergic neurons and induced human cortical GABAergic interneurons. By contrast, AAV9-NVVRSSS variant transduced both induced human cortical neurons and cocultured rat primary astrocytes. High viral titers (1E+5 viral genomes per cell) caused a significant decrease in viability of induced human cortical neurons. Low viral titers (1E+4 viral genomes per cell) led to a significant increase in the neuronal activity marker c-Fos in transduced human neurons following treatment with a potassium channel blocker. Conclusions: We identified two engineered AAV capsid variants that efficiently transduce induced human cortical neurons. The threefold higher percentage of c-Fos positive, transduced human neurons may indicate functional alterations induced by viral transduction and/or transgene expression.