No abstract

The gene Prph2 encodes a photoreceptor-specific membrane glycoprotein, peripherin-2 (also known as peripherin/rds), which is inserted into the rims of photoreceptor outer segment discs in a complex with rom-1 (ref. 2). The complex is necessary for the stabilization of the discs, which are renewed constantly throughout life, and which contain the visual pigments necessary for photon capture. Mutations in Prph2 have been shown to result in a variety of photoreceptor dystrophies, including autosomal dominant retinitis pigmentosa and macular dystrophy. A common feature of these diseases is the loss of photoreceptor function, also seen in the retinal degeneration slow (rds or Prph2 Rd2/Rd2) mouse, which is homozygous for a null mutation in Prph2. It is characterized by a complete failure to develop photoreceptor discs and outer segments, downregulation of rhodopsin and apoptotic loss of photoreceptor cells. The electroretinograms (ERGs) of Prph2Rd2/Rd2 mice have greatly diminished a-wave and b-wave amplitudes, which decline to virtually undetectable concentrations by two months. Subretinal injection of recombinant adeno-associated virus (AAV) encoding a Prph2 transgene results in stable generation of outer segment structures and formation of new stacks of discs containing both perpherin-2 and rhodopsin, which in many cases are morphologically similar to normal outer segments. Moreover, the re-establishment of the structural integrity of the photoreceptor layer also results in electrophysiological correction. These studies demonstrate for the first time that a complex ultrastructural cell defect can be corrected both morphologically and functionally by in vivo gene transfer.

The retinal degeneration slow (rds or Prph2(Rd2/Rd2)) mouse, a model of recessive retinitis pigmentosa, lacks a functional gene encoding peripherin 2. This membrane glycoprotein is required for the formation of photoreceptor outer segment discs. The striking feature of the rds mouse is the complete failure to develop outer segments. We have previously examined the short-term effect of gene replacement therapy using an adeno-associated (AAV) vector and demonstrated induction of outer segments and improvement of photoreceptor function. Here we have extended our analysis and have demonstrated that the potential for ultrastructural improvement is dependent upon the age at which animals are treated, but the effect of a single injection on photoreceptor ultrastructure may be long-term. However, there was no significant effect on photoreceptor cell loss, irrespective of the date of administration, despite the improvements in morphology and function. Our investigation excluded procedure-related damage, vector toxicity and immune responses as major factors which might counteract the benefits of photoreceptor restoration, but suggested that transgene over-expression is of significance. These findings suggest that successful gene therapy in patients with photoreceptor defects may ultimately depend upon intervention in early stages of disease and upon accurate control of transgene expression.

During retinal degeneration, microglia are activated and express sialoadhesin. The temporal relationship between photoreceptor apoptosis and microglial response suggests that microglia are not responsible for the initial wave of photoreceptor death, and this is corroborated by the absence of iNOS and nitrotyrosine. Expression of sialoadhesin may indicate blood-retinal barrier breakdown, which has immune implications for subretinal gene therapeutic strategies.

Purpose To compare treatment efficacy of anti-VEGF medications following pro re nata (PRN, "as needed", monthly injections only in case of active disease) or treat and extend (T&E, progressive extension of treatment intervals up to 12 weeks depending on the clinical findings) treatment protocols in real-world conditions. Methods Retrospective, observational study. Patients diagnosed with age-related macular degeneration and without pre-treatment undergoing routine anti-VEGF treatment in one eye clinic in Switzerland were included. Treatment was performed according to local practices, using ranibizumab or aflibercept, and following T&E or PRN regimens. Changes in logMAR and injection intervals (time between two injections) for specific treatment periods were evaluated descriptively and using mixed models. Results In total, 1071 patients with 1332 treated eyes (ranibizumab/PRN 722, ranibizumab/T&E 191, aflibercept/T&E 419) were included in the analyses. At baseline, logMAR (mean ± SD) was similar in both ranibizumab treatment groups (PRN 0.63 ± 0.43, T&E 0.57 ± 0.42). In the ranibizumab/PRN group, logMAR was about 0.1 lower for all time intervals in the initial and maintenance phases in comparison with baseline, indicating an improvement in VA. By comparison, logMAR improved more strongly in the ranibizumab/T&E group (16 to < 22 months, − 0.19 [− 0.23-0.15]) in comparison with baseline. Comparing ranibizumab/T&E vs. aflibercept/T&E groups, improvements in logMAR were similar over time. In the maintenance phase, the rate of patients with a clinically relevant improvement in visual acuity (> 0.2 logMAR) was higher in both T&E groups compared with the ranibizumab/PRN group. Injection intervals in the maintenance phase in ranibizumab/T&E group gradually expanded over time; whereas in the aflibercept/T&E group, injection intervals remained relatively stable. Conclusions Ranibizumab used according to T&E protocol yielded a stronger improvement in logMAR, compared with PRN protocol with longer injection intervals than aflibercept/T&E. This large real-world data assessment supports previous data on the superiority of T&E treatment. Keywords Age-related macular degeneration (AMD). Pro re nata (PRN). Treat and extend (T&E). Anti-VEGF treatment .

Using confocal microscopy we have examined in detail the temporal and spatial pattern of green fluorescent protein expression following sub-retinal injection of recombinant adeno-associated virus (rAAV) in the mouse and have determined the effect of viral titre on the number and type of cells transduced. Our results suggest that some transgene expression occurs as early as three days after injection, and that transgene expression occurs beyond the area of retinal detachment. Vector titre appears to have a substantial effect on both transduction efficiency and the speed of onset of photoreceptor cell transduction. Our data suggests that we have not yet reached the limits of photoreceptor transduction efficiency using AAV vectors. An increase in titre could still lead to an improved transduction efficiency and faster onset of photoreceptor transduction. We failed to detect transfected cones even in areas where nearly 100% of the rods were transduced, but we found efficient and sustained RPE transduction.

Disruption of the homeostatic properties of secreted APP with consecutive Abeta cytotoxicity might be a contributing factor of ganglion cell loss in glaucomatous mouse retinas.

Autoimmune posterior uveitis is a chronic, potentially blinding inflammatory disease of the eye. It is commonly treated with immunosuppressive drugs that have adverse long-term effects. Advances in gene transfer techniques have enabled long-term, stable transduction of retinal cells following subretinal injection with adeno-associated viral (AAV) vectors. Here we report for the first time that subretinal injection of rAAV-2 encoding murine IL-10 into the retina of C57BL/6 mice significantly decreases the median experimental autoimmune uveitis (EAU) disease severity. This protection is shown to be due to a decrease in the number and activation status of infiltrating monocytes during EAU, as determined by costimulatory molecule expression and nitrotyrosine detection. No differences within splenocyte proliferative responses or serum antibody levels were detected, emphasizing the potential of gene therapy strategies in ameliorating autoimmune responses in local microenvironments without unwanted systemic effects.