A Retrospective Longitudinal Study of 460 Patients with ABCA4-Associated Retinal Disease.

PURPOSE: To investigate the distribution of genotypes and natural history of ABCA4-associated retinal disease in a large cohort of patients seen at a single institution. DESIGN: Retrospective, single-institution cohort review. PARTICIPANTS: Patients seen at the University of Iowa between November 1986 and August 2022 clinically suspected to have disease caused by sequence variations in ABCA4. METHODS: DNA samples from participants were subjected to a tiered testing strategy progressing from allele-specific screening to whole genome sequencing. Charts were reviewed, and clinical data were tabulated. The pathogenic severity of the most common alleles was estimated by studying groups of patients who shared 1 allele. Groups of patients with shared genotypes were reviewed for evidence of modifying factor effects. MAIN OUTCOME MEASURES: Age at first uncorrectable vision loss, best-corrected visual acuity, and the area of the I2e isopter of the Goldmann visual field. RESULTS: A total of 460 patients from 390 families demonstrated convincing clinical features of ABCA4-associated retinal disease. Complete genotypes were identified in 399 patients, and partial genotypes were identified in 61. The median age at first vision loss was 16 years (range, 4-76 years). Two hundred sixty-five families (68%) harbored a unique genotype, and no more than 10 patients shared any single genotype. Review of the patients with shared genotypes revealed evidence of modifying factors that in several cases resulted in a > 15-year difference in age at first vision loss. Two hundred forty-one different alleles were identified among the members of this cohort, and 161 of these (67%) were found in only a single individual. CONCLUSIONS: ABCA4-associated retinal disease ranges from a very severe photoreceptor disease with an onset before 5 years of age to a late-onset retinal pigment epithelium-based condition resembling pattern dystrophy. Modifying factors frequently impact the ABCA4 disease phenotype to a degree that is similar in magnitude to the detectable ABCA4 alleles themselves. It is likely that most patients in any cohort will harbor a unique genotype. The latter observations taken together suggest that patients' clinical findings in most cases will be more useful for predicting their clinical course than their genotype. FINANCIAL DISCLOSURE(S): Proprietary or commercial disclosure may be found in the Footnotes and Disclosures at the end of this article.

Using Goldmann Visual Field Volume to Track Disease Progression in Choroideremia.

Purpose: Choroideremia is an X-linked choroidopathy caused by pathogenic variants in the CHM gene. It is characterized by the early appearance of multiple scotomas in the peripheral visual field that spread and coalesce, usually sparing central vision until late in the disease. These features make quantitative monitoring of visual decline particularly challenging. Here, we describe a novel computational approach to convert Goldmann visual field (GVF) data into quantitative volumetric measurements. With this approach, we analyzed visual field loss in a longitudinal, retrospective cohort of patients with choroideremia. Design: Single-center, retrospective, cohort study. Participants: We analyzed data from 238 clinic visits of 56 molecularly-confirmed male patients with choroideremia from 41 families (range, 1-27 visits per patient). Patients had a median follow up of 4 years (range, 0-56 years) with an age range of 5 to 76 years at the time of their visits. Methods: Clinical data from molecularly-confirmed patients with choroideremia, including GVF data, were included for analysis. Goldmann visual field records were traced using a tablet-based application, and the 3-dimensional hill of vision was interpolated for each trace. This procedure allowed quantification of visual field loss from data collected over decades with differing protocols, including different or incomplete isopters. Visual acuity (VA) data were collected and converted to logarithm of the minimum angle of resolution values. A delayed exponential mixed-effects model was used to evaluate the loss of visual field volume over time. Main Outcome Measures: Visual acuity and GVF volume. Results: The estimated mean age at disease onset was 12.6 years (standard deviation, 9.1 years; 95% quantile interval, 6.5-36.4 years). The mean field volume loss was 6.8% per year (standard deviation, 4.5%; 95% quantile interval, 1.9%-18.8%) based on exponential modeling. Field volume was more strongly correlated between eyes (r2 = 0.935) than best-corrected VA (r2 = 0.285). Conclusions: Volumetric analysis of GVF data enabled quantification of peripheral visual function in patients with choroideremia and evaluation of disease progression. The methods presented here may facilitate the analysis of historical GVF data from patients with inherited retinal disease and other diseases associated with visual field loss. This work informs the creation of appropriate outcome measures in choroideremia therapeutic trials, particularly in trial designs. Financial Disclosures: Proprietary or commercial disclosure may be found in the Footnotes and Disclosures at the end of this article.

AUTOIMMUNE RETINOPATHY MIMICKING HERITABLE RETINAL DEGENERATION IN A PATIENT WITH COMMON VARIABLE IMMUNE DEFICIENCY.

PURPOSE: 1) To describe a case of autoimmune retinopathy mimicking heritable photoreceptor degeneration in a patient with common variable immune deficiency and 2) to investigate the humoral and cell-mediated branches of the immune system in this patient to better understand the mechanism of immune-mediated photoreceptor damage in this disease. METHODS: Retrospective chart review with evaluation of multimodal imaging, genotype analysis, and investigation of circulating autoantibodies and T-cell response to retinal antigens. RESULTS: A 40-year-old woman with bilateral, progressive vision loss was referred for evaluation of a possible inherited retinal degeneration. She was found to have asymmetric peripheral visual field constriction, cystoid macular edema, vitreous cells, and bone spicule-like pigmentary changes in both eyes. An extensive workup for underlying infectious or inflammatory causes was unrevealing, and molecular analysis for heritable retinal degeneration failed to identify a plausible disease-causing genotype. Screening for antiretinal antibodies showed the presence of multiple antiretinal antibodies, consistent with a diagnosis of autoimmune retinopathy. Immunologic workup demonstrated markedly decreased levels of serum IgA and IgG, consistent with common variable immune deficiency. T-cells isolated from the patient showed increased proliferation when stimulated with human retinal proteins, supporting a role for both cell- and humoral-mediated autoimmunity. Treatment with mycophenolate mofetil and intravenous immunoglobin therapy slowed the progression of disease and resulted in preservation of her central vision. CONCLUSION: Autoimmune retinopathy can be seen in common variable immune deficiency and has clinical findings similar to heritable photoreceptor degeneration. Both the humoral and cellular immune responses are involved in the pathophysiology. Immune modulatory therapy has stabilized the disease course in this patient and may play an important role in the management of autoimmune retinopathy.

Development and biological characterization of a clinical gene transfer vector for the treatment of MAK-associated retinitis pigmentosa.

By combining next generation whole exome sequencing and induced pluripotent stem cell (iPSC) technology we found that an Alu repeat inserted in exon 9 of the MAK gene results in a loss of normal MAK transcript and development of human autosomal recessive retinitis pigmentosa (RP). Although a relatively rare cause of disease in the general population, the MAK variant is enriched in individuals of Jewish ancestry. In this population, 1 in 55 individuals are carriers and one third of all cases of recessive RP is caused by this gene. The purpose of this study was to determine if a viral gene augmentation strategy could be used to safely restore functional MAK protein as a step toward a treatment for early stage MAK-associated RP. Patient iPSC-derived photoreceptor precursor cells were generated and transduced with viral vectors containing the MAK transcript. One week after transduction, transcript and protein could be detected via rt-PCR and western blotting respectively. Using patient-derived fibroblast cells and mak knockdown zebra fish we demonstrate that over-expression of the retinal MAK transgene restored the cells ability to regulate primary cilia length. In addition, the visual defect in mak knockdown zebrafish was mitigated via treatment with the retinal MAK transgene. There was no evidence of local or systemic toxicity at 1-month or 3-months following subretinal delivery of clinical grade vector into wild type rats. The findings reported here will help pave the way for initiation of a phase 1 clinical trial for the treatment of patients with MAK-associated RP.

Genetic Association between MMP9 and Choroidal Neovascularization in Age-Related Macular Degeneration.

Purpose: To evaluate the first association specific to exudative age-related macular degeneration (AMD) located near the matrix metalloproteinase 9 (MMP9) gene. Design: Genetic association study. Participants: One thousand seven hundred twelve patients with AMD (672 nonexudative, 1040 exudative) of predominantly northern European descent seeking treatment at the University of Iowa Hospitals and Clinics. Methods: We reanalyzed the International AMD Genetics Consortium (IAMDGC) data to validate the association of polymorphisms near MMP9 with exudative AMD and to identify additional associated single nucleotide polymorphisms (SNPs), especially MMP9 coding sequence SNPs. We genotyped a cohort of 1712 AMD patients from Iowa with 3 SNPs identified with our analysis of the IAMDGC cohort using commercially available real-time quantitative polymerase chain reaction (PCR) assays. Firth regression was used to measure the association between MMP9 SNP genotypes and exudative AMD in our cohort of patients from Iowa. In addition, we developed a PCR-based assay to genotype the Iowa cohort at a short tandem repeat polymorphism (STRP) at the MMP9 locus. Main Outcome Measures: Odds ratios and P values for exudative compared with nonexudative AMD patients in the Iowa cohort for MMP9 SNPs (rs4810482, rs17576, and rs17577) and STRP. Results: We identified 3 SNPs in the MMP9 locus (rs4810482, rs17576, and rs17577) that are highly associated with exudative AMD in patient cohorts of the IAMDGC. These MMP9 SNPs also are associated with exudative AMD in the cohort of 1712 AMD patients from Iowa (rs4810482: odds ratio [OR], 0.82; P = 0.010; rs17576: OR, 0.86; P = 0.046; and rs17577: OR, 0.80; P = 0.041). We also genotyped the cohort of AMD patients from Iowa at rs142450006, another MMP9 polymorphism that previously was associated with exudative AMD. We detected a 4bp STRP, (TTTC)n, at the rs142450006 locus that is highly polymorphic and associated significantly with exudative AMD (OR, 0.78; P = 0.016). Conclusions: This study independently confirms and expands an association between the MMP9 locus and exudative AMD, further implicating a role for extracellular matrix abnormalities in choroidal neovascularization.

Assessment of Adeno-Associated Virus Serotype Tropism in Human Retinal Explants.

Advances in the discovery of the causes of monogenic retinal disorders, combined with technologies for the delivery of DNA to the retina, offer enormous opportunities for the treatment of previously untreatable blinding diseases. However, for gene augmentation to be most effective, vectors that have the correct cell-type specificity are needed. While animal models are very useful, they often exhibit differences in retinal cell surface receptors compared to the human retina. This study evaluated the use of an ex vivo organotypic explant system to test the transduction efficiency and tropism of seven different adeno-associated virus type 2 (AAV2) serotypes in the human retina and retinal pigment epithelium-choroid-AAV2/1, AAV2/2, AAV2/4, AAV2/5, AAV2/6, AAV2/8, and AAV2/9-all driving expression of GFP under control of the cytomegalovirus promoter. After 7 days in culture, it was found that AAV2/4 and AAV2/5 were particularly efficient at transducing photoreceptor cells and that AAV2/5 was highly specific to the outer nuclear layer, whereas AAV2/8 displayed consistently low transduction of photoreceptors. To validate the authenticity of the organotypic culture system, the transduction of the same set of AAVs was also compared in a pig model, in which sub-retinal injections in vivo were compared to cultured and transduced organotypic cultures ex vivo. This study shows how different AAV serotypes behave in the human retina and provides insight for further investigation of each of these serotypes for gene augmentation-based treatment of inherited retinal degeneration.