title: iNKT/CD1d-antitumor immunotherapy significantly increases the efficacy of therapeutic CpG/peptide-based cancer vaccine.
abstract: BACKGROUND
  Therapeutic cancer vaccines aim to boost the natural immunity against transformed cancer cells, and a series of adjuvants and co-stimulatory molecules have been proposed to enhance the immune response against weak self-antigens expressed on cancer cells. For instance, a peptide/CpG-based cancer vaccine has been evaluated in several clinical trials and was shown in pre-clinical studies to favor the expansion of effector T versus Tregs cells, resulting in a potent antitumor activity, as compared to other TLR ligands. Alternatively, the adjuvant activity of CD1d-restricted invariant NKT cells (iNKT) on the innate and adaptive immunity is well demonstrated, and several CD1d glycolipid ligands are under pre-clinical and clinical evaluation. Importantly, additive or even synergistic effects have been shown upon combined CD1d/NKT agonists and TLR ligands. The aim of the present study is to combine the activation and tumor targeting of activated iNKT, NK and T cells.
  
  
  METHODS
  Activation and tumor targeting of iNKT cells via recombinant α-galactosylceramide (αGC)-loaded CD1d-anti-HER2 fusion protein (CD1d-antitumor) is combined or not with OVA peptide/CpG vaccine. Circulating and intratumoral NK and H-2Kb/OVA-specific CD8 responses are monitored, as well as the state of activation of dendritic cells (DC) with regard to activation markers and IL-12 secretion. The resulting antitumor therapy is tested against established tumor grafts of B16 melanoma cells expressing human HER2 and ovalbumin.
  
  
  RESULTS
  The combined CD1d/iNKT antitumor therapy and CpG/peptide-based immunization leads to optimized expansion of NK and OVA-specific CD8 T cells (CTLs), likely resulting from the maturation of highly pro-inflammatory DCs as seen by a synergistic increase in serum IL-12. The enhanced innate and adaptive immune responses result in higher tumor inhibition that correlates with increased numbers of OVA-specific CTLs at the tumor site. Antibody-mediated depletion experiments further demonstrate that in this context, CTLs rather than NK cells are essential for the enhanced tumor inhibition.
  
  
  CONCLUSIONS
  Altogether, our study in mice demonstrates that αGC/CD1d-antitumor fusion protein greatly increases the efficacy of a therapeutic CpG-based cancer vaccine, first as an adjuvant during T cell priming and second, as a therapeutic agent to redirect immune responses to the tumor site.
authors.affiliation: Translational Tumor Immunology Group, Ludwig Center for Cancer Research, University of Lausanne, Lausanne, Switzerland.
authors.forename: Stéphanie
authors.initials: S
authors.lastname: Corgnac
authors.affiliation: Translational Tumor Immunology Group, Ludwig Center for Cancer Research, University of Lausanne, Lausanne, Switzerland.
authors.forename: Rachel
authors.initials: R
authors.lastname: Perret
authors.affiliation: Translational Tumor Immunology Group, Ludwig Center for Cancer Research, University of Lausanne, Lausanne, Switzerland.
authors.forename: Lianjun
authors.initials: L
authors.lastname: Zhang
authors.affiliation: Department of Biochemistry, University of Lausanne, Lausanne, Switzerland.
authors.forename: Jean-Pierre
authors.initials: JP
authors.lastname: Mach
authors.affiliation: Translational Tumor Immunology Group, Ludwig Center for Cancer Research, University of Lausanne, Lausanne, Switzerland.
authors.forename: Pedro
authors.initials: P
authors.lastname: Romero
authors.affiliation: Translational Tumor Immunology Group, Ludwig Center for Cancer Research, University of Lausanne, Lausanne, Switzerland.
authors.forename: Alena
authors.initials: A
authors.lastname: Donda
keywords: CD1d; Combined cancer immunotherapy; CpG-based vaccine; iNKT cells