Regulatory T cells induced by rAAV carrying the forkhead box P3 gene prevent autoimmune thyroiditis in mice

CD4+CD25+ regulatory T (Treg) cells are immunosuppressive and help maintain peripheral immune tolerance. The forkhead/winged helix family member, Foxp3, has been shown to be a critical regulator of CD4+CD25+ Treg cells. We demonstrate by quantitative real-time PCR that CD4+CD25+ T cells express higher levels of Foxp3 mRNA than other T cell populations. Recombinant adeno-associated virus vector carrying mouse Foxp3 gene under the control of the CMV promoter was generated and used to transduce CD4+CD25- T cells. These Foxp3-transduced T cells are similar to naturally occurring CD4+CD25+ regulatory T cells which show anergy and immunosuppressive activity in vitro. Furthermore, these Foxp3-transduced T cells prevent autoimmune thyroiditis transferred by pathogenic T cells in vivo. Our data indicates that Foxp3-transduced CD4+CD25- T cells may open new therapeutic strategies for immune disorders.