Ocular Disease
The gene therapy refers to the treatment of human diseases using genetic methods that introduce a healthy copy of a flawed gene or correction of a modified gene to restore normal biological functions. Adeno-associated virus (AAV) vectors stem from non-enveloped and non-pathogenic replication-defective parvovirus and have been regarded as a safe, efficient tool for gene transfer. As a skillful expert in this field, Creative Biolabs provides multiple AAV vector design and development services in a diversity of tissues and organs, including retina, eyes, livers, skeletal muscles, etc. For ocular diseases, our one-stop, customized services enable the AAV vector trafficking to target cells for gene expression is stable, effective, and associated with few inflammatory or immune responses.
Current Research
Gene therapy is being pursued as a strategy for many genetic diseases, of which ocular disorders are extremely attractive targets for this type of approach. Single genes responsible for a number of ocular disease conditions have been identified, for example, inherited blindness. The first FDA-approved gene therapy product (voretigene neparvovec-rzyl) for an inherited disease is an AAV-based vector for a form of blindness.
Figure 1. Adeno-associated virus serotype 1 (AAV1) structure. (Rodrigues, 2018)
The eyes have well-defined anatomy with an enclosed space that offers unique strengths for local delivery, including the capacity to directly visualize and access the tissue. At the bottom of the eyes, retinal cells are post-mitotic, allowing for continued gene expression without the need for genomic integration of the transgenes. Improvements of AAV vector design and delivery routes, and selection of optimal timing for intervention will extend the success of retinal therapy to increasing inherited blinding situations. Moreover, the blood-ocular barrier contributes to the ocular immune privilege and restricts immunologic activities to this gene therapy.
AAV Vector Design for Ocular Disease at Creative Biolabs
AAV is built of single-stranded DNA, either positive- or negative-sensed, which is approximately 4.8 kilobases long. Its genome contains two open reading frames (ORFs), cap and rep, and inverted terminal repeats (ITRs) at both ends of the DNA strand. This approach highlights a range of advantages as a delivery system, such as retinal cell transduction characteristics. It has also been thought of a predominant vector for several ocular-related therapies, including Age-related macular degeneration, Achromatopsia, Choroideremia, Leber congenital amaurosis, and Retinitis pigmentosa.
Figure 2. Dual AAV vectors for large gene delivery to the retina. (Trapani, 2018)
There're 12 different AAV serotypes identified in primates to date, and most of them are commonly used in gene therapy studies. Various AAV serotypes differ in their capsid components and thus show distinct cellular tropism, transduction efficiency, and immunogenicity. Notably, AAV serotype 1, 2, 4, 5, 6, 7, 8, and 9, all reveal tropism for retinal tissues. At Creative Biolabs, our popular AAV vector design services include but not limited to:
- Recombinant AAV (rAAV) vectors are designed for ocular therapy by replacing the cap and rep genes with the transgene cassette. The cap and rap ORFs are then provided in trans during AAV production using helper plasmids. We have constructed rAAV2, the first serotype applied in gene delivery, to efficiently transduce retinal pigment epithelial and retinal ganglion cells.
- Hybrid or "pseudotyped" AAV vectors are produced by exchanging capsid proteins between different AAV serotypes. Pseudotyping not only helps to achieve the desired tropism and enhanced transduction efficiency, but also helps circumvent pre-existing immunity to certain AAV serotypes that may affect the efficacy and safety of gene therapy. All AAV pseudotypes transduce retinal pigment epithelia, with AAV2/1, AAV2/4, and AAV2/6 being the most specific. In contrast, only AAV2/5, AAV2/7, AAV2/8, and AAV2/9 transduce photoreceptors efficiently.
- AAV vector arrays have been expanded beyond natural serotypes as second-generation vectors. This tool is designed or isolated to display altered tropism and greater transduction efficiency, and two approaches used for these novel vectors are rational design and directed evolution.
As gene therapy is explored as a treatment modality for ocular diseases, the development of AAV-mediated therapy is also rapidly progressing to assist scientists in establishing a powerful new class of therapeutic products. To generate vectors for delivering genes of interest, Creative Biolabs offers professional services from the perspective of both product design and pharmaceutical development to produce AAV-based vectors targeting ocular tissues with higher safety, efficiency, and specificity. For more information, please feel free to contact us or directly send us an online inquiry.
References
- Rodrigues, G.A.; et al. (2018). Pharmaceutical development of AAV-based gene therapy products for the eye. Pharm Res. 36(2): 29.
- Trapani, I.; et al. (2018). Seeing the light after 25 years of retinal gene therapy. Trends Mol Med. 24(8): 669-681.
