Induction of Cross-Priming of Naive CD8+ T Lymphocytes by Recombinant Bacillus Calmette-Guérin That Secretes Heat Shock Protein 70-Major Membrane Protein-II Fusion Protein

摘要

Because Mycobacterium bovis bacillus Calmette-Guérin (BCG) unconvincingly activates human naive CD8+ T cells, a rBCG (BCG-70M) that secretes a fusion protein comprising BCG-derived heat shock protein (HSP)70 and Mycobacterium leprae -derived major membrane protein (MMP)-II, one of the immunodominant Ags of M. leprae , was newly constructed to potentiate the ability of activating naive CD8+ T cells through dendritic cells (DC). BCG-70M secreted HSP70-MMP-II fusion protein in vitro, which stimulated DC to produce IL-12p70 through TLR2. BCG-70M-infected DC activated not only memory and naive CD8+ T cells, but also CD4+ T cells of both types to produce IFN-γ. The activation of these naive T cells by BCG-70M was dependent on the MHC and CD86 molecules on BCG-70M-infected DC, and was significantly inhibited by pretreatment of DC with chloroquine. Both brefeldin A and lactacystin significantly inhibited the activation of naive CD8+ T cells by BCG-70M through DC. Thus, the CD8+ T cell activation may be induced by cross-presentation of Ags through a TAP- and proteosome-dependent cytosolic pathway. When naive CD8+ T cells were stimulated by BCG-70M-infected DC in the presence of naive CD4+ T cells, CD62LlowCD8+ T cells and perforin-producing CD8+ T cells were efficiently produced. MMP-II-reactive CD4+ and CD8+ memory T cells were efficiently produced in C57BL/6 mice by infection with BCG-70M. These results indicate that BCG-70M activated DC, CD4+ T cells, and CD8+ T cells, and the combination of HSP70 and MMP-II may be useful for inducing better T cell activation.