Christine N. Kay

Targeting Photoreceptors via Intravitreal Delivery Using Novel, Capsid-Mutated AAV Vectors

Development of viral vectors capable of transducing photoreceptors by less invasive methods than subretinal injection would provide a major advancement in retinal gene therapy. We sought to develop novel AAV vectors optimized for photoreceptor transduction following intravitreal delivery and to develop methodology for quantifying this transduction in vivo. Surface exposed tyrosine (Y) and threonine (T) residues on the capsids of AAV2, AAV5 and AAV8 were changed to phenylalanine (F) and valine (V), respectively. Transduction efficiencies of self-complimentary, capsid-mutant and unmodified AAV vectors containing the smCBA promoter and mCherry cDNA were initially scored in vitro using a cone photoreceptor cell line. Capsid mutants exhibiting the highest transduction efficiencies relative to unmodified vectors were then injected intravitreally into transgenic mice constitutively expressing a Rhodopsin-GFP fusion protein in rod photoreceptors (Rho-GFP mice). Photoreceptor transduction was quantified by fluorescent activated cell sorting (FACS) by counting cells positive for both GFP and mCherry. To explore the utility of the capsid mutants, standard, (non-self-complementary) AAV vectors containing the human rhodopsin kinase promoter (hGRK1) were made. Vectors were intravitreally injected in wildtype mice to assess whether efficient expression exclusive to photoreceptors was achievable. To restrict off-target expression in cells of the inner and middle retina, subsequent vectors incorporated multiple target sequences for miR181, an miRNA endogenously expressed in the inner and middle retina. Results showed that AAV2 containing four Y to F mutations combined with a single T to V mutation (quadY−F+T−V) transduced photoreceptors most efficiently. Robust photoreceptor expression was mediated by AAV2(quadY−F+T−V) −hGRK1−GFP. Observed off-target expression was reduced by incorporating target sequence for a miRNA highly expressed in inner/middle retina, miR181c. Thus we have identified a novel AAV vector capable of transducing photoreceptors following intravitreal delivery to mouse. Furthermore, we describe a robust methodology for quantifying photoreceptor transduction from intravitreally delivered AAV vectors.

Autosomal Recessive Vitelliform Macular Dystrophy In a Large Cohort Of Vitelliform Macular Dystrophy Patients

Purpose: To report 11 cases of autosomal recessive vitelliform macular dystrophy and to compare their molecular findings and phenotypic characteristics with those of patients with the more common and well-described dominant form of the disease. Methods: Blood samples were obtained from 435 unrelated individuals with a clinical diagnosis of vitelliform macular dystrophy and screened for mutations in the coding sequences of BEST1. Medical records and retinal photographs of selected patients were reviewed. Results: Nine of the 435 probands were found to have 2 plausible disease-causing variations in BEST1, while 198 individuals were found to have heterozygous variations compatible with autosomal dominant inheritance. Inheritance phase was determined in three of the recessive families. Six novel disease-causing mutations were identified among these recessive patients: Arg47Cys, IVS7−2A>G, IVS7+4G>A, Ile205del12ATCCTGCTCCAGAG, Pro274Arg, and Ile366delCAGGTGTGGC. Forty-four novel disease-causing mutations were identified among the patients with presumed autosomal dominant disease. The phenotype of patients with recessive alleles for BEST1 ranged from typical vitelliform lesions to extensive extramacular deposits. Conclusion: The authors provide evidence that two abnormal BEST1 alleles, neither of which causes macular disease alone, can act in concert to cause early-onset vitelliform macular dystrophy.

Three-dimensional Distribution of the Vitelliform Lesion, Photoreceptors, and Retinal Pigment Epithelium in the Macula of Patients With Best Vitelliform Macular Dystrophy

OBJECTIVE To describe the anatomical phenotypes of Best vitelliform macular dystrophy (BVMD) with spectral-domain optical coherence tomography (SD-OCT) in a large series of patients with confirmed mutations in the BEST1 gene. METHODS In our retrospective observational case series, we assessed 15 patients (30 eyes) with a clinical diagnosis of vitelliform macular dystrophy who were found to have mutations in the BEST1 gene. Color fundus photographs and SD-OCT images were evaluated and compared with those of 15 age-matched controls (30 eyes). Using a validated 3-dimensional SD-OCT segmentation algorithm, we calculated the equivalent thickness of photoreceptors and the equivalent thickness of the retinal pigment epithelium for each patient. The photoreceptor equivalent thickness and the retinal pigment epithelium (RPE) equivalent thickness were compared in all patients, in a region of the macula outside the central lesion for patients with BVMD and outside the fovea in control patients. Paired t tests were used for statistical analysis. RESULTS The SD-OCT findings revealed that the vitelliform lesion consists of material above the RPE and below the outer segment tips. Additionally, drusen-like deposition of sub-RPE material was notable, and several patients exhibited a sub-RPE fibrotic nodule. Patients with BVMD had a mean photoreceptor equivalent thickness of 28.3 μm, and control patients had a mean photoreceptor equivalent thickness of 21.8 μm, a mean difference of 6.5 μm (P < .01), whereas the mean RPE equivalent thickness was not statistically different between patients with BVMD and control patients (P = .53). CONCLUSIONS The SD-OCT findings suggest that vitelliform material is located in the subretinal space and that BVMD is associated with diffuse photoreceptor outer segment abnormalities overlying a structurally normal RPE. CLINICAL RELEVANCE These findings provide new insight into the pathophysiology of BVMD and thus have implications for the development of therapeutic interventions.

AAV-Mediated Gene Therapy in the Guanylate Cyclase (RetGC1/RetGC2) Double Knockout Mouse Model of Leber Congenital Amaurosis

Mutations in GUCY2D are associated with recessive Leber congenital amaurosis-1 (LCA1). GUCY2D encodes photoreceptor-specific, retinal guanylate cyclase-1 (RetGC1). Reports of retinal degeneration in LCA1 are conflicting; some describe no obvious degeneration and others report loss of both rods and cones. Proof of concept studies in models representing the spectrum of phenotypes is warranted. We have previously demonstrated adeno-associated virus (AAV)-mediated RetGC1 is therapeutic in GC1ko mice, a model exhibiting loss of cones only. The purpose of this study was to characterize AAV-mediated gene therapy in the RetGC1/RetGC2 double knockout (GCdko) mouse, a model lacking rod and cone function and exhibiting progressive loss of both photoreceptor subclasses. Use of this model also allowed for the evaluation of the functional efficiency of transgenic RetGC1 isozyme. Subretinal delivery of AAV8(Y733F) vector containing the human rhodopsin kinase (hGRK1) promoter driving murine Gucy2e was performed in GCdko mice at various postnatal time points. Treatment resulted in restoration of rod and cone function at all treatment ages and preservation of retinal structure in GCdko mice treated as late as 7 weeks of age. Functional gains and structural preservation were stable for at least 1 year. Treatment also conferred cortical- and subcortical-based visually-guided behavior. Functional efficiency of transgenic RetGC1 was indistinguishable from that of endogenous isozyme in congenic wild-type (WT) mice. This study clearly demonstrates AAV-mediated RetGC1 expression restores function to and preserves structure of rod and cone photoreceptors in a degenerative model of retinal guanylate cyclase deficiency, further supporting development of an AAV-based vector for treatment of LCA1.

Assessing photoreceptor structure in retinitis pigmentosa and usher syndrome

Purpose The purpose of this study was to examine cone photoreceptor structure in retinitis pigmentosa (RP) and Usher syndrome using confocal and nonconfocal split-detector adaptive optics scanning light ophthalmoscopy (AOSLO). Methods Nineteen subjects (11 RP, 8 Usher syndrome) underwent ophthalmic and genetic testing, spectral-domain optical coherence tomography (SD-OCT), and AOSLO imaging. Split-detector images obtained in 11 subjects (7 RP, 4 Usher syndrome) were used to assess remnant cone structure in areas of altered cone reflectivity on confocal AOSLO. Results Despite normal interdigitation zone and ellipsoid zone appearance on OCT, foveal and parafoveal cone densities derived from confocal AOSLO images were significantly lower in Usher syndrome compared with RP. This was due in large part to an increased prevalence of non-waveguiding cones in the Usher syndrome retina. Although significantly correlated to best-corrected visual acuity and foveal sensitivity, cone density can decrease by nearly 38% before visual acuity becomes abnormal. Aberrantly waveguiding cones were noted within the transition zone of all eyes and corresponded to intact inner segment structures. These remnant cones decreased in density and increased in diameter across the transition zone and disappeared with external limiting membrane collapse. Conclusions Foveal cone density can be decreased in RP and Usher syndrome before visible changes on OCT or a decline in visual function. Thus, AOSLO imaging may allow more sensitive monitoring of disease than current methods. However, confocal AOSLO is limited by dependence on cone waveguiding, whereas split-detector AOSLO offers unambiguous and quantifiable visualization of remnant cone inner segment structure. Confocal and split-detector thus offer complementary insights into retinal pathology.

Uveitis following intravitreal bevacizumab: a non-infectious cluster.

BACKGROUND AND OBJECTIVE In this retrospective case series, the authors report seven cases of bevacizumab-related uveitis that occurred within a 4-month period. PATIENTS AND METHODS Seven eyes of six patients developed non-infectious uveitis following bevacizumab intravitreal injections in a cohort of 978 consecutive bevacizumab injections. RESULTS The mean age of patients was 74.6 years (range: 26 to 92). All patients developed symptom onset within 1 day of injection. Shared signs and symptoms included corneal edema, anterior chamber and vitreous cell, conjunctival injection, ocular pain, and lack of hypopyon. In all patients, visual acuity returned to within one line of baseline acuity. All seven eyes had been previously injected with bevacizumab, with a mean number of antecedent injections of 6.1 (range: 3 to 12). CONCLUSION A cluster of sterile bevacizumab-related uveitic reactions was described in this case series. Acute onset of symptoms, absence of hypopyon, a predominant anterior segment reaction, and prompt improvement on topical steroid therapy are useful clinical features distinguishing this uveitic syndrome from infectious endophthalmitis.

Long-term follow-up for efficacy and safety of treatment of retinitis pigmentosa with valproic acid

Aims The purpose of this study was to determine the long-term efficacy and safety of valproic acid (VPA) treatment in patients with pigmentary retinal dystrophies. Methods A retrospective chart review was conducted on 31 patients with a diagnosis of pigmentary retinal dystrophy prescribed VPA at a single centre. Visual field (VF), visual acuity (VA), length of treatment, liver enzymes and side effects were analysed. VF areas were defined using Goldmann VF (GVF) tracings recorded before, during and after VPA treatment using the V4e isopter for each eye. Using custom software, planimetric areas of VF were calculated. Results Five of the patients (10 eyes) had two Goldmann VF tracings, allowing comparison between baseline and follow-up VF. After 9.8 months of VPA, VF decreased by 0.145 cm2 (26.478%) (p=0.432). For 22 of the patients (41 eyes), VA data was available, and logarithm of the minimum angle of resolution (logMAR) score changed by 0.056 log units (representing a decline in VA) after 14.9 months on VPA (p=0.002). Twelve patients (38.7%) reported negative side effects related to VPA use. Conclusions VPA plays a complex role in patients with pigmentary retinal dystrophies and may be associated with VA and field decline as well as adverse side effects. Physicians should use caution with using VPA for pigmentary retinal dystrophies.

REPEATABILITY AND LONGITUDINAL ASSESSMENT OF FOVEAL CONE STRUCTURE IN CNGB3-ASSOCIATED ACHROMATOPSIA.

Purpose: Congenital achromatopsia is an autosomal recessive disease causing substantial reduction or complete absence of cone function. Although believed to be a relatively stationary disorder, questions remain regarding the stability of cone structure over time. In this study, the authors sought to assess the repeatability of and examine longitudinal changes in measurements of central cone structure in patients with achromatopsia. Methods: Forty-one subjects with CNGB3-associated achromatopsia were imaged over a period of between 6 and 26 months using optical coherence tomography and adaptive optics scanning light ophthalmoscopy. Outer nuclear layer (ONL) thickness, ellipsoid zone (EZ) disruption, and peak foveal cone density were assessed. Results: ONL thickness increased slightly compared with baseline (0.184 &mgr;m/month, P = 0.02). The EZ grade remained unchanged for 34/41 subjects. Peak foveal cone density did not significantly change over time (mean change 1% per 6 months, P = 0.126). Conclusion: Foveal cone structure showed little or no change in this group of subjects with CNGB3-associated achromatopsia. Over the time scales investigated (6–26 months), achromatopsia seems to be a structurally stable condition, although longer-term follow-up is needed. These data will be useful in assessing foveal cone structure after therapeutic intervention.

Photoreceptor recovery following laser photocoagulation and albendazole in diffuse unilateral subacute neuroretinitis.

Methods. This was a retrospective record review of all patients undergoing Collaborative Ocular Melanoma Study– style brachytherapy at the Eye Institute of the Medical College of Wisconsin between January 1, 1996, and December 31, 2007. Institutional review board approval was obtained. Patients were identified by billing record search. Exclusion criteria included being younger than 18 years, having nonmelanotic tumors, and having incomplete medical documentation. The following data were gathered: preoperative IOP, age, sex, history of DM or glaucoma, tumor location and height, radiation dose, plaque diameter, daily IOP during brachytherapy, muscle disinsertion, and use of topical antiglaucoma medications.

Ocular injuries sustained in paintball trauma

Dear Editor, Similar to the article published earlier this year by Pahk and associates, we reviewed the charts of 12 patients who sustained ocular injuries secondary to blunt paintball trauma. Traumatic hyphema was the most common associated ocular injury, present in nine patients, which corroborated Pahk’s findings as well as previous reports [1, 2]. Lens subluxation was seen in two patients, open globe in three patients (all classified as “ruptures” by standardized ocular trauma classification system) [3], angle recession in three patients, vitreous hemorrhage in seven patients, retinal detachment in four patients, and retinal tear or dialysis without detachment in two patients (Table 1). The average number of injuries per patient was 4.3, and ten of the 12 patients had two or more types of injuries. The most common surgery was a pars plana vitrectomy, performed in seven eyes (Table 2). Final visual outcomes ranged from 20/20 to no light perception, and six eyes ended with 20/ 400 vision or worse. Paintball is a popular recreational sport, existing in both commercial and noncommercial settings [4]. Eye protective gear is mandatory in most commercial settings; however, most injuries associated with paintballs are incurred in noncommercial, unsupervised war-game settings when masks are not worn [5]. The retrospective nature of our study precluded our ability to ascertain if masks had been worn by our patients; however, it is very unlikely that the types of eye injuries our patients sustained could have occurred if masks were worn appropriately. The eyegear that is worn today in a commercialized paintball setting has been extensively studied and regulated. The American Society of Testing and Materials (ASTM) has approved manufacturer guidelines for 2.5 mm thickness polycarbonate lenses to be used for protective eyewear in paintball games [6]. Eyegear must be capable of withstanding a direct hit from a paintball traveling at well over 300 feet per second (91 m/s, or approximately 201 mph). All manufactured paintball masks must satisfy the ASTM F1776-99a standards, which must be visibly labelled on all paintball mask packaging. Anti-fogging technology is available. Thermal lenses are marketed as “no-fog lenses” and are more costly than “fog-resistant” lenses, which require use of an anti-fogging applicant. This anti-fogging feature of lenses is important, as fogging is a common reason stated for mask removal [5]. Currently, a consumer can buy a paintball gun online with no restrictions. Paintball-induced injuries could probably be significantly reduced if some of the following steps were taken: