CD27 Agonism Plus PD-1 Blockade Recapitulates CD4+ T-cell Help in Therapeutic Anticancer Vaccination

T. Ahrends, N. Baba a, Y. Xiao, H. Yagita, H. van Eenennaam, J. Borst
2016 Cancer Research  
While showing promise, vaccination strategies to treat cancer require further optimization. Likely barriers to efficacy involve cancer-associated immunosuppression and peripheral tolerance, which limit the generation of effective vaccine-specific cytotoxic T lymphocytes (CTL). Because CD4 þ T cells improve CTL responsiveness, next-generation vaccines include helper epitopes. Here, we demonstrate in mice how CD4 þ T-cell help optimizes the CTL response to a clinically relevant DNA vaccine
more » ... red to combat human papillomavirus-expressing tumors. Inclusion of tumor-unrelated helper epitopes greatly increased CTL priming, effector, and memory T-cell programming. CD4 þ T-cell help optimized the CTL response in all these aspects via CD27/CD70 costimulation. Notably, administration of an agonistic CD27 antibody could largely replace helper epitopes in promoting primary and memory CTL responses, acting directly on CD8 þ T cells. CD27 agonism improved efficacy of the vaccine without helper epitopes, more so than combined PD-1 and CTLA-4 blockade. Combining CD27 agonism with CTLA-4 blockade improved vaccine-induced CTL priming and tumor infiltration, but only combination with PD-1 blockade was effective at eradicating tumors, thereby fully recapitulating the effect of CD4 þ T-cell help on vaccine efficacy. PD-1 blockade alone did not affect CTL priming or tumor infiltration, so these results implied that it cooperated with CD4 þ T-cell help by alleviating immune suppression against CTL in the tumor. Helper epitope inclusion or CD27 agonism did not stimulate regulatory T cells, and vaccine efficacy was also improved by CD27 agonism in the presence of CD4 þ T-cell help. Our findings provide a preclinical rationale to apply CD27 agonist antibodies, either alone or combined with PD-1 blockade, to improve the therapeutic efficacy of cancer vaccines and immunotherapy generally. Cancer Res; 76(10); 2921-31. Ó2016 AACR.
doi:10.1158/0008-5472.can-15-3130 pmid:27020860 fatcat:xlxbthu4jvdxpirwwf3lofyfzm