June 2023
Volume 64, Issue 8
Open Access
ARVO Annual Meeting Abstract  |   June 2023
Understanding the mechanism of retinal inflammation following subretinal gene therapy
Author Affiliations & Notes
  • Kanmin Xue
    Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, Oxfordshire, United Kingdom
    Oxford Eye Hospital, Oxford University Hospitals NHS Foundation Trust, Oxford, Oxfordshire, United Kingdom
  • Footnotes
    Commercial Relationships   Kanmin Xue None
  • Footnotes
    Support  Wellcome Trust CRCD Fellowship: 216593/Z/19/Z
Investigative Ophthalmology & Visual Science June 2023, Vol.64, 790. doi:
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      Kanmin Xue; Understanding the mechanism of retinal inflammation following subretinal gene therapy. Invest. Ophthalmol. Vis. Sci. 2023;64(8):790.

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      © ARVO (1962-2015); The Authors (2016-present)

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Abstract

Purpose : Retinal inflammation is frequently encountered following viral vector-mediated retinal gene therapy. It could have deleterious effects on the vulnerable photoreceptors in inherited retinal diseases and is increasingly recognized as a major determinant of clinical success.

Methods : Clinical data from dose-escalating trials of AAV vector-mediated subretinal gene therapies are reviewed. Retinal imaging from cases of gene therapy-associated uveitis is correlated with observations in mouse models treated with subretinal AAV vectors expressing fluorescent marker, therapeutic transgene, or sham. At early and late timepoints (up to 6 weeks), retinal gene expression was analyzed by RT-qPCR. Retinal immune cells (including resident microglia and infiltrating leukocytes) were quantified by retina dissociation and multiparameter flow cytometry. The effects of hydroxychloroquine (19 μM) were assessed by subretinal co-injection with AAV vector.

Results : Observations from multiple clinical trials indicate that the severity and duration of gene therapy-associated retinal inflammation correlate with increasing vector dose (typically ≥1011 gp/ml). OCT findings suggest blood-retinal barrier breakdown and immune cell infiltration of the retina. In mice, subretinal AAV gene therapy leads to activation of pattern recognition receptors (e.g. Toll-like receptors) and release of pro-inflammatory cytokines (Tnf-α, Ifn-γ) by day 7, followed by retinal infiltration by monocytic phagocytes, CD8+/CD4+ T cells and natural killer cells by week 6. The latter is indicative of type 1 immunity typically seen against intracellular viruses or in rheumatoid arthritis. We detect significant AAV transduction of microglia which may be a trigger for cytokine release and leukocyte recruitment. Finally, subretinal co-administration of the DMARD, hydroxychloroquine, with AAV led to a 3-fold enhancement of viral transduction in vivo, supporting its potential as a clinical adjunct for gene therapy.

Conclusions : Retinal inflammation in gene therapy correlates with vector dose. It is characterized by activation of anti-viral innate immunity and type 1 cell-mediated response, potentially orchestrated via microglia activation. The use of targeted immunomodulatory adjunct during retinal gene therapy may allow lower vector dose, prevent retinal inflammation, and improve clinical outcomes.

This abstract was presented at the 2023 ARVO Annual Meeting, held in New Orleans, LA, April 23-27, 2023.

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