Alteration of the surface glycosylation pattern on malignant cells potentially affects tumor immunity by directly influencing interactions with glycan-binding proteins (lectins) on the surface of immunomodulatory cells. The sialic acid-binding Ig-like lectins Siglec-7 and -9 are MHC class I-independent inhibitory receptors on human NK cells that recognize sialic acid-containing carbohydrates. Here, we found that the presence of Siglec-9 defined a subset of cytotoxic NK cells with a mature phenotype and enhanced chemotactic potential. Interestingly, this Siglec-9 + NK cell population was reduced in the peripheral blood of cancer patients. Broad analysis of primary tumor samples revealed that ligands of Siglec-7 and -9 were expressed on human cancer cells of different histological types. Expression of Siglec-7 and -9 ligands was associated with susceptibility of NK cell-sensitive tumor cells and, unexpectedly, of presumably NK cell-resistant tumor cells to NK cellmediated cytotoxicity. Together, these observations have direct implications for NK cell-based therapies and highlight the requirement to consider both MHC class I haplotype and tumor-specific glycosylation.

ReviewTargeting the immune system Dendritic cells (DCs) play crucial roles in promoting and regulating immune defenses, providing important targets for prophylactic and therapeutic approaches (FiguRe 1). Particulate formulations, including liposomes and other nanoparticles, have been employed as delivery vehicles. Despite the large number of reports, current in-depth knowledge on the cellular processes involved remains relatively limited, particularly for nucleic acid delivery. Certain structures in the nucleic acid may also signal the cell in the sense of an adjuvant or immunomodulatory activity. Importantly, the optimized characteristics for delivery of an antigen or therapeutic agent may be distinct from those for nucleic acid delivery, especially RNA species. Moreover, RNA delivery for interference therapy will not necessarily require the same delivery routes as mRNA delivery wherein RNA translation is the main requisite.The efficacy of delivery can be further improved by targeting the appropriate cells of the immune system, an area in which nanoparticle-based delivery platforms have found an important niche [1]. Advances with prophylactic applications can also prove valuable for therapeutic applications and vice versa, as seen with RNA delivery. This review will consider how growing knowledge on delivery mechanisms has found application with nucleic acids, in both prophylaxis and therapy, focusing on interaction with DCs.The initial components of the DC endocytic pathways are critically important in determining how the cell handles the delivered material; thereafter, correct cytosolic delivery is a critical element for a number of desired outcomes, including delivery of nucleic acids. Advances made with protein delivery -in particular, vaccines -are of value to highlight the potential of a particular mode of application or the high risk for nucleic acid integrity. Particularly pertinent is the application of cationic elements in the delivery mechanisms and how application of ligands for cell receptors influence intracellular compartmentalization.It is not the aim of the present review to retrace all the fine details of work contributing to our current knowledge. Accordingly, review articles covering areas that have already received considerable attention will be employed and assimilated to provide a more elaborate picture of the current situation. This will allow a focusing on more recent advances, along with problems and pitfalls therein. While advances on protein and DNA delivery will be presented, these will be used to highlight how our current knowledge can be applied to RNA delivery. There are numerous reviews on protein delivery to DC, wherein many of the procedures employed are not relevant for RNA delivery, which must escape into the cytosol undamaged. With DNA delivery, there is also the question of whether the DNA will activate the DC or reach the nucleus for transcription; this latter area has most often Functional RNA delivery targeted to dendritic cells by synthetic nanoparticles Dendritic cell...

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Self-amplifying replicon RNA (RepRNA) possesses high potential for increasing antigen load within dendritic cells (DCs). The major aim of the present work was to define how RepRNA delivered by biodegradable, chitosan-based nanoparticulate delivery vehicles (nanogel-alginate (NGA)) interacts with DCs, and whether this could lead to translation of the RepRNA in the DCs. Although studies employed virus replicon particles (VRPs), there are no reports on biodegradable, nanoparticulate vehicle delivery of RepRNA. VRP studies employed cytopathogenic agents, contrary to DC requirements—slow processing and antigen retention. We employed noncytopathogenic RepRNA with NGA, demonstrating for the first time the efficiency of RepRNA association with nanoparticles, NGA delivery to DCs, and RepRNA internalization by DCs. RepRNA accumulated in vesicular structures, with patterns typifying cytosolic release. This promoted RepRNA translation, in vitro and in vivo. Delivery and translation were RepRNA concentration-dependent, occurring in a kinetic manner. Including cationic lipids with chitosan during nanoparticle formation enhanced delivery and translation kinetics, but was not required for translation of immunogenic levels in vivo. This work describes for the first time the characteristics associated with chitosan-nanoparticle delivery of self-amplifying RepRNA to DCs, leading to translation of encoded foreign genes, namely influenza virus hemagglutinin and nucleoprotein.

IFN-I production is a characteristic of HIV/SIV primary infections. However, acute IFN-I plasma concentrations rapidly decline thereafter. Plasmacytoid dendritic cells (pDC) are key players in this production but primary infection is associated with decreased responsiveness of pDC to TLR 7 and 9 triggering. IFNα production during primary SIV infection contrasts with increased pDC death, renewal and dysfunction. We investigated the contribution of pDC dynamics to both acute IFNα production and the rapid return of IFNα concentrations to pre-infection levels during acute-to-chronic transition. Nine cynomolgus macaques were infected with SIVmac251 and IFNα-producing cells were quantified and characterized. The plasma IFN-I peak was temporally associated with the presence of IFNα+ pDC in tissues but IFN-I production was not detectable during the acute-to-chronic transition despite persistent immune activation. No IFNα+ cells other than pDC were detected by intracellular staining. Blood-pDC and peripheral lymph node-pDC both lost IFNα− production ability in parallel. In blood, this phenomenon correlated with an increase in the counts of Ki67+-pDC precursors with no IFNα production ability. In tissues, it was associated with increase of both activated pDC and KI67+-pDC precursors, none of these being IFNα+ in vivo. Our findings also indicate that activation/death-driven pDC renewal rapidly blunts acute IFNα production in vivo: pDC sub-populations with no IFNα-production ability rapidly increase and shrinkage of IFNα production thus involves both early pDC exhaustion, and increase of pDC precursors.