PFA-fixed Hsp60sp-loaded dendritic cells as a vaccine for the control of mouse experimental allergic encephalomyelitis.

We have shown that Hsp60sp-loaded immature dendritic cells (DC/sp) can protect mice from the induction of experimental allergic encephalomyelitis (EAE) by inducing Qa-1-restricted CD8(+) T regulatory (Treg) cells. The binding half-life between Qa-1 and Hsp60sp is particularly short and leads to an unstable Qa-1/peptide complex that significantly decreases the efficacy of this vaccination. To prevent Qa-1/Hsp60sp complex dissociation, we utilized paraformaldehyde (PFA) fixation to stabilize the formation of the Qa-1/Hsp60sp complex and maximize the function of DC/sp as a vaccine to control autoimmune diseases. Compared with the non-fixed DC/sp, the fixed DC/sp (FDC/sp) showed an enhanced ability to activate Qa-1-restricted Hsp60sp-specific CD8(+)T cells in vitro and prevented EAE in vivo. Importantly, the FDC/sp maintained immune activity following cryopreservation for 1 week or after storage for 72 h at 4 °C. These results indicate that PFA fixation can sustain or increase the efficacy of DC/sp by improving the stability of the Qa-1/Hsp60sp complex on the surface of the DC/sp. In addition, PFA fixation creates a time window for DC/sp storage, transport and application. Our data suggest a potential clinical use of FDC/sp as a vaccine for the prevention and treatment of autoimmune disease.