Enhanced efficacy of regulatory T cell transfer against increasing resistance, by elevated foxp3 expression induced in arthritic murine hosts

Objective. To investigate the efficacy of type II collagen-reactive Foxp3-expressing T cell transfer in suppressing collagen-induced arthritis (CIA) in relation to disease progression. Methods. CD3-activated CD4 T cells were retro-virally transduced with the Foxp3 gene, and their in vitro suppressive activity on T cell proliferation was assessed for correlation with Foxp3 levels. To suppress CIA, Foxp3-transduced T cells generated with type II collagen- or ovalbumin (OVA)-pulsed dendritic cells (DCs), which were fractionated by Foxp3 levels, were adoptively transferred to mice at various time points. Results. The in vitro suppressive activity of Foxp3-transduced cells correlated positively with Foxp3 levels. Type II collagen-reactive, but not OVA-reactive, Foxp3-transduced cells significantly suppressed CIA when they were transferred before immunization, and this suppression was accompanied by decreased anti-type II collagen antibody production. Larger cell numbers were required to suppress CIA when transfer occurred 20 days after immunization, indicating that hosts became resistant to suppression. Transfer of 1 x 105 Foxp3low cells had only a marginal effect on CIA suppression in immunized hosts, while transfer of Foxp3high cells at smaller doses significantly suppressed CIA. Transfer of 1 x 105 Foxp3high cells after establishment of arthritis attenuated disease progression but did not reverse joint swelling. Conclusion. Resistance to Foxp3-transduced T cells proceeded as CIA progressed, suggesting that late-stage aggressive arthritis is more resistant to regulatory T cell transfer. An elevated expression level of Foxp3 in type II collagen-specific T cells improved their suppressive function in CIA. Thus, transfer of T cells expressing high levels of Foxp3 could be a strategy to overcome the induced resistance to regulatory T cell therapy.