Safety of Same-Eye Subretinal Sequential Readministration of AAV2-hRPE65v2 in Non-human Primates

Abstract

We have demonstrated safe and effective subretinal readministration of recombinant adeno-associated virus serotype (rAAV) to the contralateral eye in large animals and humans even in the setting of preexisting neutralizing antibodies (NAbs). Readministration of AAV to the same retina may be desirable in order to treat additional areas of the retina not targeted initially or to boost transgene expression levels at a later time point. To better understand the immune and structural consequences of subretinal rAAV readministration to the same eye, we administered bilateral subretinal injections of rAAV2-hRPE65v2 to three unaffected non-human primates (NHPs) and repeated the injections in those same eyes 2 months later. Ophthalmic exams and retinal imaging were performed after the first and second injections. Peripheral blood monocytes, serum, and intraocular fluids were collected at baseline and post-injection time points to characterize the cellular and humoral immune responses. Histopathologic and immunohistochemical studies were carried out on the treated retinas. Ipsilateral readministration of AAV2-hRPE65v2 in NHPs did not threaten the ocular or systemic health through the time span of the study. The repeat injections were immunologically and structurally well tolerated, even in the setting of preexisting serum NAbs. Localized structural abnormalities confined to the outer retina and retinal pigmented epithelium (RPE) after readministration of the treatment do not differ from those observed after single or contralateral administration of an AAV carrying a non-therapeutic transgene in NHPs and were not observed in a patient treated with the nearly identical, FDA-approved, AAV2-hRPE65v2 vector (voretigene neparvovec-rzyl), suggesting NHP-specific abnormalities.

Immune Responses to Viral Gene Therapy Vectors

“…Likely facilitated by the immune privilege of the eye, vector administration to one eye could be later on followed by contralateral gene transfer to the second eye, and repeat administration to the same eye is also possible. 37 , 38 Other routes of in vivo vector administration are more typically associated with formation of NABs that prevent re-administration of vector. Furthermore, humans develop NABs to various serotypes during childhood.…”

Short-term assessment of subfoveal injection of AAV2-hCHM gene augmentation in choroideremia using adaptive optics ophthalmoscopy

“…Altogether, our results provide safety information at the cellular level for both the surgical technique and the AAV2-hCHM study agent confirming histologic/cellular-level safety signals that up to now were only available through histopathologic studies in normal non-human primates. [48][49][50][51][52] The subretinal injection however, is not without risk. Foveal thinning and the occurrence of full thickness loss of retinal tissue (macular holes) are known complications of the procedure.…”

Adeno-Associated Viruses (AAV) and Host Immunity – A Race Between the Hare and the Hedgehog

“…Likewise, transient antibody response against the capsid and cellular immune responses were also noted [reviewed in (30,76,213)]. The low to mild and transient immune responses allowed repeated administration of AAV vectors, either contralateral or in one eye (214,215) or the delivery of two boluses in the same eye (216). Finally, long-term expression could be achieved in most clinical trials, with a decline observed in some after a few years (202,210) [reviewed in (30,76,213)].…”