It has been argued that the priming of T cells directed to the transgene product may be somehow defective after rAAVmediated gene transfer (Lin et al., 2007a,b) . However, in our experimental settings, transduced muscle fibers progressively disappear in the absence of immunoregulatory treatment ( Figure 2D) . Further, we show that even after CTLA-4/Ig alone or in combination therapies, an anti-Ova immune response is evidenced in ELISpot assays and in an in vivo model of tumor rejection upon adoptive transfer of T cells in recipient animals (Figure 4) . Hence, forced up-regulation of PD-1 ligands in muscle cells yielded a level of protection of transduced cells from the cytotoxic assault Frontiers in Microbiology | Microbial Immunology of circulating anti-Ova lymphocytes and provided in combination therapy a means to prolong transgene persistence and transcription. Therefore, CTLA-4/Ig plus PD-L1/2 combination therapy represents a candidate approach to circumvent the bottleneck of immune responses directed toward the transgene product and may deserve further investigation for non-secreted transgenic protein models and in larger animals.