Recombinant fusion proteins for targeting dendritic cell subsets in therapeutic cancer vaccine.

Dendritic cells (DCs) are professional antigen-presenting cells, which are optimal for the priming of a T cell response against pathogens and tumors. Therefore, many efforts are made to develop therapeutic cancer vaccines which preferentially target the antigen to DC subsets. To this aim, we developed two types of recombinant fusion proteins, which favor antigen delivery to pro-inflammatory DCs as well as the crosstalk between specialized subpopulations of DCs. The first approach combines peptide/CpG vaccination with the recruitment of iNKT cells to the tumor site via CD1d-antitumor scFv fusion proteins. The second approach is targeting the tumor antigen to cross-presenting Xcr1 <sup>+</sup> DCs via a fusion protein made of Xcl1 fused to a synthetic long peptide followed by an IgG1 Fc fragment. Both strategies allow a potent tumor-specific CD8 T cell response associated with tumor regression or tumor growth delay depending on the model. In the case of iNKT cell activation, the strategy relies on a strong IL-12 release by splenic DCs, while in the second case, the T cell response is strictly dependent on the presence of Xcr1 <sup>+</sup> cross-presenting DCs