Autoantibodies detection in patients affected by autoimmune retinopathies

OBJECTIVE

Autoimmune retinopathies (ARs) encompass a spectrum of immune diseases that are characterized by the presence of autoantibodies against retinal proteins in the bloodstream. These autoantibodies (AAbs) lead to a progressive and sometimes rapid loss of vision. ARs commonly affect subjects over 50 years of age, but also rare cases of kids under 3 years of age have been reported.

PATIENTS AND METHODS

In this study, 47 unrelated Caucasian patients were enrolled. All subjects showed negative cancer diagnoses and negative results in their genetic screenings. We studied 8 confirmed retinal antigens using Western blotting analysis, with α-enolase followed by carbonic anhydrase II being the two most frequently found in the patients' sera.

RESULTS

Nineteen patients were positive (40.4%), thirteen uncertain (27.7%), and fifteen were negative (31.9%). Their gender did not correlate with the presence of AAbs (p=0.409).

CONCLUSIONS

AAbs are responsible for retinal degeneration in some cases, while in others, they contribute to exacerbating the progression of the disease; however, their detection is crucial to reaching a better diagnosis and developing more effective treatments for these conditions. Moreover, finding good biomarkers is important not only for AR monitoring and prognosis, but also for helping with early cancer diagnosis.

Misdiagnosis of X-linked retinitis pigmentosa in a choroideremia patient with heavily pigmented fundi

Inherited retinal diseases are thought to be the leading cause of sight loss in the working age population. Mutations found in the RPGR and CHM genes cause retinitis pigmentosa (RP) and choroideremia, respectively. In the first instance, an X-linked family history of visual field loss commonly raises the suspicion of one of these two genes. In choroideremia, the classic description of a white fundal reflex secondary to the widespread chorioretinal degeneration was made over a hundred years ago in Caucasians. But, it is not so obvious in heavily pigmented fundi. Hence, the clinical diagnosis of CHM in non-Caucasian patients may be challenging in the first stages of the disease. Here we report a case of a Southeast Asian gentleman who has a family history of X-linked retinal degeneration and was found to have a confirmed in-frame deletion of 12 DNA nucleotides in exon 15 of the RPGR gene. Later in life, however, his fundal appearance showed unusual areas of circular pigment hypertrophy and clumping. He was therefore tested for carrying a disease-causing mutation in the CHM gene and a null mutation was found. Since gene therapy trials are ongoing for both of these conditions, it has now become critically important to establish the correct genetic diagnosis in order to recruit suitable candidates. Moreover, this case demonstrates the necessity to remain vigilant in the interpretation of genetic results which are inconsistent with clinical features.

Technique of retinal gene therapy: delivery of viral vector into the subretinal space

PurposeSafe and reproducible delivery of gene therapy vector into the subretinal space is essential for successful targeting of the retinal pigment epithelium (RPE) and photoreceptors. The success of surgery is critical for the clinical efficacy of retinal gene therapy. Iatrogenic detachment of the degenerate (often adherent) retina in patients with hereditary retinal degenerations and small volume (eg, 0.1 ml) subretinal injections pose new surgical challenges.MethodsOur subretinal gene therapy technique involved pre-operative planning with optical coherence tomography (OCT) and autofluorescence (AF) imaging, 23 G pars plana vitrectomy, internal limiting membrane staining with Membrane Blue Dual (DORC BV, Zuidland, Netherlands), a two-step subretinal injection using a 41 G Teflon tipped cannula (DORC) first with normal saline to create a parafoveal bleb followed by slow infusion of viral vector via the same self-sealing retinotomy. Surgical precision was further enhanced by intraoperative OCT (Zeiss Rescan 7000, Carl Zeiss Meditec AG, Jena, Germany). Foveal functional and structural recovery was evaluated using best-corrected Early Treatment Diabetic Retinopathy Study (ETDRS) visual acuity, microperimetry and OCT.ResultsTwo patients with choroideremia aged 29 (P1) and 27 (P2) years, who had normal and symmetrical levels of best-corrected visual acuity (BCVA) in both eyes, underwent unilateral gene therapy with the fellow eye acting as internal control. The surgeries were uncomplicated in both cases with successful detachment of the macula by subretinal vector injection. Both treated eyes showed recovery of BCVA (P1: 76-77 letters; P2: 84-88 letters) and mean threshold sensitivity of the central macula (P1: 10.7-10.7 dB; P2: 14.2-14.1 dB) to baseline within a month. This was accompanied by normalisation of central retinal thickness on OCT.ConclusionsHerein we describe a reliable technique for subretinal gene therapy, which is currently used in clinical trials to treat choroideremia using an adeno-associated viral (AAV) vector encoding the CHM gene. Strategies to minimise potential complications, such as avoidance of excessive retinal stretch, air bubbles within the injection system, reflux of viral vector and post-operative vitritis are discussed.