Whereas a single dose of CTLA-4/Ig was efficient to suppress the systemic immune response at day 14 ( Figures 3A,B left panels), this was not the case when further monitoring the immune response at day 40. Indeed, anti-Ova CD8 + T cell expansion as well as anti-Ova IgG immune responses were readily detectable at day 40 in mice that had received rAAV2/1-Ova and CTLA-4/Ig at day 0 ( Figures 3A,B) . Therefore, early suppression of immune priming by a single dose of CTLA-4/Ig is not sufficient to permanently wipe out the immune responses against transgene product in these experimental conditions. Instead, continuous production of sOva by transduced muscle cells sensitizes the immune response at later time points when CTLA-4/Ig has been cleared from the circulation of treated mice.