To investigate the in vivo immunomodulatory potential of CTLA-4/Ig and rAAV2/1-PD-L1, we either administered 200 μg of CTLA-4/Ig i.p. or co-injected rAAV2/1-PD-L1 i.m. at the same time as rAAV2/1-Ova, and monitored the cellular and humoral immune response 14 day after. Results showed that even a single dose of CTLA-4/Ig was efficient to completely prevent the priming of anti-Ova CD8 + T cells (Figure 2C , left panel) and the apparition of anti-Ova IgG in the serum of treated animals ( Figure 2C , middle panel). Accordingly, this immunosuppressive treatment allowed a sustained sOva production that could be assayed in the serum at day 14 whereas it was undetectable in controls ( Figure 2C right panel). We concluded from these data that transient immunosuppression by a single dose of CTLA-4/Ig is very efficient to prevent the priming of the cellular and humoral response at early time points after AAV transduction.