454. Prior AAV2-hIL10 Infusion Decreases AAV9-Dependent Immunotoxicity in Rat Brain

Cerebral infusion of AAV9 vectors encoding non-self proteins results in the initiation of a robust immune reaction at the site of injection due to the vector's ability to transduce antigen-presenting cells in the brain [1]. Infusion of AAV9 encoding a human gene, aromatic L-amino acid decarboxylase (hAADC), elicited an initial innate immune activation at the site of infusion that was succeeded by a robust adaptive immune response that included generation of hAADC antibodies, lymphocytic infiltration and cell-mediated elimination of transduced cells in the brain. In this study, we investigated whether the potent anti-inflammatory cytokine, human interleukin-10 (hIL10) could suppress this immune response. Four weeks prior to unilateral infusion of AAV9-hAADC into rat striatum, we infused AAV2-hIL10 bilaterally into striatum (control rats received bilaterally injection of AAV2-GFP). Six weeks after AAV9-hAADC injection, control rats revealed robust amphetamine-induced ipsilateral rotational behavior (956±203 (S.D.) turns/1 hour). In while, in AAV2-hIL10-treated rats ipsilateral rotations were reduced by 66 % compared with control rats and this effect persisted for at least 8 weeks. This neuroprotective effect of hIL10 was evident histologically. The number of surviving neurons (NeuN) was significantly increased in AAV2-hIL10-treated animals compared to AAV2-GFP-treated controls, and microglial and astrocytic activation was diminished. Whereas, in control rats, a significant number of hAADC-positive astrocytes was observed (GFAP/hAADC double fluorescent staining), astrocytic transduction in AAV2-hIL10-treated rats was almost completely suppressed. This somewhat puzzling result may be due to an effect of IL10 on astrocytic expression of an AAV9 receptor required for transduction. However, our findings suggest that expression of IL-10 in the brain may be a useful adjunctive therapy in the treatment of neurological diseases in which the expression of a foreign antigen is unavoidable.