Treg depletion followed by intracerebral CpG-ODN injection induce brain tumor rejection

•Immunotherapy by anti-CD25 mAb and CpG of brain tumor•NK cells implication in brain tumor rejection induced by anti-CD25 and CpG injection•Anti-CD25 and CpG injection allow brain tumor rejection.

Using brain lymphoma model, we demonstrate that immunotherapy combining Treg depletion (using anti-CD25 mAb PC61) followed by intracranial CpG-ODN administration induced tumor rejection in all treated mice and led to the establishment of a memory antitumor immune response in 60% of them. This protective effect was associated with a recruitment of NK cells and, to a lesser extent, of dendritic cells, B cells and T lymphocytes. NK cell depletion abolished the protective effect of the treatment, confirming a major role of NK cells in brain tumor elimination. Each treatment used alone failed to protect brain tumor bearing mice, revealing the therapeutic benefit of combining Treg depletion and local CpG-ODN injection.