Leber’s Congenital Amaurosis (LCA) is a genetically inherited desease of the photoreceptors in the human retina. The patients loose light perception in their third decade of life due to a mutation in the protein retinal pigment epithelium–specific 65-kDa protein gene (RPE65) (Albert M. Maguire et al, 2008 NEJM). [PubMed] The consortium of institutions performing this study used adeno-associated virus (AAV) carrying RPE65 complementary DNA (cDNA) in an approch of subretinal delivery. AAV is considered safe for gene therapy, since it is not associated with desease and since it belongs to the family of dependoviruses, it depends on the presence of adenovirus to replicate. This trait can easily be deactivated in gene therapeutic applications.
The safety of genetically altered virus to deliver gene therapeutic DNA has been debated thoroughly in the last decade and either promising as well as shocking examples have been published. In this case, the virus was applied local, reducing the risk further in comparison to systemic applications.
In this study, three patients were treated with genetically modified AAV and in all three, an improvement in retinal function has been observed. This is a new approach, giving the rationale to further explore the opportunities of gene therapy. But one should not forget, that these vectors are all potential pathogens and despite vigorous safety measures, they bare the ability to adapt to changing situations.
In my opinion, this field is still lacking a safe and specifically directable “shuttle”, which doesn´t integrate its DNA in the host genome, thereby reducing the risk of integrational mutagenesis.
Popularity: 1% [?]