OR07
Study of retinal microglial cells after sub-retinal injection of recombinant AAV in pigs
J B Ducloyer(1,2) G Le Meur(1,2) J Demilly(1) A Pereira(1) L Libeau(1,2) A Mellet(1) D Chevalier-Leray(3) F Roux(3) V Blouin(1) T Larcher(1) E Toublanc(1) P Hulin(4) O Adjali(1) M Weber(1,2) T Cronin(1)
1:Inserm U1089; 2:University Hospital of Nantes; 3:Oniris; 4:Inserm
Microglial cells are involved in the pathogenesis of numerous retinal pathologies and possibly in inflammatory reactions secondary to sub-retinal injections of recombinant Adeno-Associated Viral vectors (rAAV). The aim of this study is to assess the transduction and the recruitment of microglial cells after subretinal injection in pigs.
Subretinal injection of rAAV was performed in the eyes of Yucatan pigs using either rAAV8-CAG-EGFP, n=1, rAAV6-CAG-EGFP, n=3 (150µl, 4,5e11 vg) or saline, n=2. In vivo and post-mortem retinal imaging were done one month after injection.
Immediately after surgery, there was no signs of inflammation or toxicity. Optical coherence tomography (OCT) did not show any structural difference between injected zone (IZ) and non-injected zone (NIZ) in most pigs. Green fluorescence was strong in IZ and absent in NIZ. Both eyes of two rAAV6-injected pigs experienced severe inflammation. Microglial Iba1+ cells were detected but none of them showed green fluorescence. They were much more numerus in IZ than in NIZ in each group. Morphologic analysis found that microglial Iba1+ cells were more often activated in rAAV6-injected pig than in rAAV8-injected pig, and even more than in controls BSS-injected pig and non-injected pig.
After subretinal injection of high dose rAAV6 or 8, microglial cells were not transduced. They were massively recruited in the IZ in each group and associated with severe inflammation in 2 rAAV6-injected pigs. It highlights the need of further research to effectively target them to treat retinal pathologies and reduce the immunogenicity of sub-retinal viral vector injections.