Messenger RNA-electroporated dendritic cells presenting MAGE-A3 simultaneously in HLA class I and class II molecules.

An optimal anticancer vaccine probably requires the cooperation of both CD4(+) Th cells and CD8(+) CTLs. A promising tool in cancer immunotherapy is, therefore, the genetic modification of dendritic cells (DCs) by introducing the coding region of a tumor Ag, of which the antigenic peptides will be presented in both HLA class I and class II molecules. This can be achieved by linking the tumor Ag to the HLA class II-targeting sequence of an endosomal or lysosomal protein. In this study we compared the efficiency of the targeting signals of invariant chain, lysosome-associated membrane protein-1 (LAMP1) and DC-LAMP. Human DCs were electroporated before or after maturation with mRNA encoding unmodified enhanced green fluorescent protein (eGFP) or eGFP linked to various targeting signals. The lysosomal degradation inhibitor chloroquine was added, and eGFP expression was evaluated at different time points after electroporation. DCs were also electroporated with unmodified MAGE-A3 or MAGE-A3 linked to the targeting signals, and the presentation of MAGE-A3-derived epitopes in the context of HLA class I and class II molecules was investigated. Our data suggest that proteins linked to the different targeting signals are targeted to the lysosomes and are indeed presented in the context of HLA class I and class II molecules, but with different efficiencies. Proteins linked to the LAMP1 or DC-LAMP signal are more efficiently presented than proteins linked to the invariant chain-targeting signal. Furthermore, DCs electroporated after maturation are more efficient in Ag presentation than DCs electroporated before maturation.