June 2020
Volume 61, Issue 7
Free
ARVO Annual Meeting Abstract  |   June 2020
Neutralising antibody responses to intravitreally delivered AAV2 and exosome-associated AAV2 vectors are associated with a failure of repeated gene transfer following vector readministration in the ipsilateral eye
Author Affiliations & Notes
  • Michael Whitehead
    Department of Clinical Neurosciences, University of Cambridge, Cambridge, United Kingdom
  • Andrew Osborne
    Department of Clinical Neurosciences, University of Cambridge, Cambridge, United Kingdom
  • Peter Widdowson
    Ikarovec Ltd, Canterbury, Kent, United Kingdom
  • Patrick Yu-Wai-Man
    Department of Clinical Neurosciences, University of Cambridge, Cambridge, United Kingdom
    NIHR Biomedical Research Centre, Moorfields Eye Hospital and UCL Institute of Ophthalmology, London, United Kingdom
  • Keith R Martin
    Centre for Eye Research Australia, Royal Victorian Eye and Ear Hospital, Melbourne, Victoria, Australia
    Department of Clinical Neurosciences, University of Cambridge, Cambridge, United Kingdom
  • Footnotes
    Commercial Relationships   Michael Whitehead, Ikarovec (F); Andrew Osborne, Astellas (F), Quethera (F); Peter Widdowson, Astellas (F), Ikarovec - CEO (E), Quethera (I); Patrick Yu-Wai-Man, GenSight (C); Keith Martin, Astellas (F), Ikarovec (I), Quethera (I)
  • Footnotes
    Support  Medical Research Council Doctoral Training Programme, Novo Nordisk UK Small Grant Award, National Eye Research Council Small Grant Award, Addenbrookes Charitable Trust Pump Priming
Investigative Ophthalmology & Visual Science June 2020, Vol.61, 2441. doi:
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      Michael Whitehead, Andrew Osborne, Peter Widdowson, Patrick Yu-Wai-Man, Keith R Martin; Neutralising antibody responses to intravitreally delivered AAV2 and exosome-associated AAV2 vectors are associated with a failure of repeated gene transfer following vector readministration in the ipsilateral eye. Invest. Ophthalmol. Vis. Sci. 2020;61(7):2441.

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

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Abstract

Purpose : Adeno-associated virus serotype 2 (AAV2) can effectively deliver therapeutic genes to the retina but anti-capsid neutralising antibody (NAb) responses may limit the effectiveness of vector readministration. Recent reports have shown that exosome-associated AAV (ExoAAV) can achieve robust transduction of numerous physiological systems in rodent and non-human primate models at low vector concentrations. We therefore investigated whether low dose ExoAAV is capable of overcoming anti-capsid NAb responses and achieving repeated gene transfer to the inner retina.

Methods : Adult C57BL/6 male mice (n=6/group) received intravitreal injections (IVT; 2mL) of either PBS vehicle, low dose AAV2-sCAG-eGFP (1E8 GC/eye), low dose ExoAAV2-sCAG-eGFP (1E8 GC/eye) or high dose AAV2-sCAG-eGFP (2E10 GC/eye). After 3 weeks, blood serum samples were collected, and all groups received a second IVT of high dose AAV2-CMV-mCherry (2E10 GC/eye) into the ipsilateral eye. Tissues were collected at 6 weeks and analysed by retinal flatmounting and cyrosectioning. Serum samples were analysed with a NAb assay, wherein lower area-under-the-curve (AUC) values denote higher NAb titres.

Results : High dose AAV2 resulted in significant increases in NAb levels vs. PBS vehicle (6.72+/-0.83 AUC vs. 35.07+/-2.29 AUC, mean+/-SEM; p<0.001) and ExoAAV2 also induced modest increases in NAb titres vs. the same control (18.30+/-1.55 AUC vs. 35.07+/-2.29 AUC, mean+/-SEM; p<0.01). We therefore hypothesised that repeated gene transfer by vector readministration would be more successful with initial IVTs of low dose ExoAAV2. However, we observed complete inhibition of mCherry expression in the ipsilateral eye following intravitreal delivery of AAV2-CMV-mCherry to eyes that had received either high dose AAV2-sCAG-eGFP or low dose ExoAAV2-sCAG-eGFP, but robust mCherry expression after an initial injection of PBS vehicle or low dose AAV2-sCAG-eGFP.

Conclusions : Our data highlights the difficulties of achieving repeated gene transfer via vector readministration strategies, even when modest increases in NAb titres are induced by the initial injection. Our studies therefore support the use of immunosuppressive regimens in preclinical and clinical studies attempting to achieve repeated gene transfer to the inner retina.

This is a 2020 ARVO Annual Meeting abstract.

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