Over-expression of Hlx homeobox gene in DC2.4 dendritic cell enhances its maturation and antigen presentation

Leishmania regulates host YY1: Comparative proteomic analysis identifies infection modulated YY1 dependent proteins

The protein Yin-Yang 1 (YY1) is a ubiquitous multifunctional transcription factor. Interestingly, there are several cellular functions controlled by YY1 that could play a role in Leishmania pathogenesis. Leishmaniasis is a human disease caused by protozoan parasites of the genus Leishmania. This study examined the potential role of macrophage YY1 in promoting Leishmania intracellular survival. Deliberate knockdown of YY1 resulted in attenuated survival of Leishmania in infected macrophages, suggesting a role of YY1 in Leishmania persistence. Biochemical fractionation studies revealed Leishmania infection caused redistribution of YY1 to the cytoplasm from the nucleus where it is primarily located. Inhibition of nuclear transport by leptomycin B attenuates infection-mediated YY1 redistribution and reduces Leishmania survival. This suggests that Leishmania induces the translocation of YY1 from the nucleus to the cytoplasm of infected cells, where it may regulate host molecules to favour parasite survival. A label-free quantitative whole proteome approach showed that the expression of a large number of macrophage proteins was dependent on the YY1 level. Interestingly, several of these proteins were modulated in Leishmania-infected cells, revealing YY1-dependent host response and suggesting their potential role in Leishmania pathogenesis. Together, this study identifies YY1 as a novel virulence factor that promotes Leishmania survival inside host macrophages.

B7-H1 maintains the polyclonal T cell response by protecting dendritic cells from cytotoxic T lymphocyte destruction

Induced B7-H1 expression in the tumor microenvironment initiates adaptive resistance, which impairs immune functions and leads to tumor escape from immune destruction. Antibody blockade of the B7-H1/PD-1 interaction overcomes adaptive resistance, leading to regression of advanced human cancers and survival benefits in a significant fraction of patients. In addition to cancer cells, B7-H1 is expressed on dendritic cells (DCs), but its role in DC functions is less understood. DCs can present multiple antigens (Ags) to stimulate dominant or subdominant T cell responses. Here, we show that immunization with multiple tumor Ag-loaded DCs, in the absence of B7-H1, vastly enhances cytotoxic T lymphocyte (CTL) responses to dominant Ag. In sharp contrast, CTL responses to subdominant Ag were paradoxically suppressed, facilitating outgrowth of tumor variants carrying only subdominant Ag. Suppressed CTL responses to subdominant Ag are largely due to the loss of B7-H1-mediated protection of DCs from the lysis of CTL against dominant Ag. Therefore, B7-H1 expression on DCs may help maintain the diversity of CTL responses to multiple tumor Ags. Interestingly, a split immunization approach, which presents dominant and subdominant Ags with different DCs, promoted CTL responses to all Ags and prevented tumor escape in murine tumor models. These findings have implications for the design of future combination cancer immunotherapies.