Abstract
Purpose :
In vivo gene therapy using viral vectors, such as Adeno-Associated Virus (AAV), represents a promising approach to treat some genetic disorders. However, immune responses directed against capsid or transgene product can limit the success of this therapeutic strategy. We propose here a novel basic approach to overcome this issue exploiting the immunological properties of the eye. Indeed, Anterior Chamber-Associated Immune Deviation (ACAID) is an antigen specific peripheral immunomodulatory mechanism triggered when an antigen is introduced into the aqueous humor of a mammalian eye. The hypothesis tested here aims to induce an ACAID mechanism leading to an inhibition of the transgene-specific cellular immune response which occurs following an intravenous infusion of an AAV coding for a specific transgene.
Methods :
We set up an experimental model of ACAID consisting in an intracameral injection of soluble peptides (DBY and UTY) from the HY male antigen into wild type female C57Bl/6 mice (H-2b background). Seven days later, an intravenous injection of a recombinant AAV2/8 vector (rAAV2/8-GFP-HY) was performed, leading to the expression of the fusion GFP-HY transgene. Cellular immune response was measured on splenocytes at different time points by IFNγ ELISpot and cytokine titration, and the cytotoxic immune response against transgene expressing cells was monitored by an in vivo cytotoxicity assay.
Results :
Anterior chamber injection of HY peptides, compared to PBS control, led to a reduction (up to 80%) of the number of IFNγ producing T-cells. In addition, cytokine secretion assay showed an impairment of the Th1 cytokine profile in ACAID condition, with a 8 and 2 fold reduction in the secretion of IFNγ and TNFα, respectively. Moreover, results of the in vivo cytotoxicity assay suggested that HY-expressing cells can survive in ACAID-induced mice.
Conclusions :
In conclusion, lymphocyte polarization impairment and inhibition of cellular cytotoxic immune responses against transgene expressing cells, indicate that ACAID seems to be a powerful inhibitory mechanism in the context of systemic gene transfer. This new basic approach exploiting the ocular immune privilege could open opportunities to regulate immune responses in the context of gene therapy.
This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.