Depending on the experimental situation, rAAV-mediated gene transfer can either lead to durable transgene expression or, conversely, to the rapid formation of neutralizing antibodies and/or destruction of transduced cells by cytotoxic cells. Several factors influencing the immune response against transgenic proteins encoded by the rAAV vectors have now been identified including host species, route of administration, vector dose, immunogenicity of the transgenic protein, inflammatory status of the host and capsid serotype (Mays and Wilson, 2011) . These factors are thought to influence immunogenicity by triggering innate immunity, cytokine production, APC maturation, antigen presentation and, ultimately, priming of naïve T lymphocytes to functional effectors. Therefore, the idea to dampen immune activation by interfering with these very mechanisms has logically emerged with the aim to induce a short-term immunosuppression, avoid the early immune priming that follows vector administration and promote long-term tolerance (Zaiss and Muruve, 2008) .