Galectin-8 activates dendritic cells and stimulates antigen-specific immune response elicitation
JOURNAL OF LEUKOCYTE BIOLOGY
Authors: Carabelli, Julieta; Quattrocchi, Valeria; D'Antuono, Alejandra; Zamorano, Patricia; Virginia Tribulatti, Maria; Campetella, Oscar
Abstract
Gal-8 is proposed as an immune-stimulator molecule that promotes an inflammatory cellular profile during elicitation of the adaptive immune response. Galectin-8 (Gal-8) is a mammalian -galactoside-binding lectin, endowed with proinflammatory properties. Given its capacity to enhance antigen-specific immune responses in vivo, we investigated whether Gal-8 was also able to promote APC activation to sustain T cell activation after priming. Both endogenous [dendritic cells (DCs)] and bone marrow-derived DCs (BMDCs) treated with exogenous Gal-8 exhibited a mature phenotype characterized by increased MHC class II (MHCII), CD80, and CD86 surface expression. Moreover, Gal-8-treated BMDCs (Gal-8-BMDCs) stimulated antigen-specific T cells more efficiently than immature BMDCs (iBMDCs). Proinflammatory cytokines IL-3, IL-2, IL-6, TNF, MCP-1, and MCP-5, as well as growth factor G-CSF, were augmented in Gal-8-BMDC conditioned media, with IL-6 as the most prominent. Remarkably, BMDCs from Gal-8-deficient mice (Lgals8(-/-) BMDC) displayed reduced CD86 and IL-6 expression and an impaired ability to promote antigen-specific CD4 T cell activation. To test if Gal-8-induced activation correlates with the elicitation of an effective immune response, soluble Gal-8 was coadministrated with antigen during immunization of BALB/cJ mice in the experimental foot-and-mouth disease virus (FMDV) model. When a single dose of Gal-8 was added to the antigen formulation, an increased specific and neutralizing humoral response was developed, sufficient to enhance animal protection upon viral challenge. IL-6 and IFN-, as well as lymphoproliferative responses, were also incremented in Gal-8/antigen-immunized animals only at 48 h after immunization, suggesting that Gal-8 induces the elicitation of an inflammatory response at an early stage. Taking together, these findings argue in favor of the use of Gal-8 as an immune-stimulator molecule to enhance the adaptive immune response.
PLA2G16 represents a switch between entry and clearance of Picornaviridae
NATURE
Authors: Staring, Jacqueline; von Castelmur, Eleonore; Blomen, Vincent A.; van den Hengel, Lisa G.; Brockmann, Markus; Baggen, Jim; Thibaut, Hendrik Jan; Nieuwenhuis, Joppe; Janssen, Hans; van Kuppeveld, Frank J. M.; Perrakis, Anastassis; Carette, Jan E.; Brummelkamp, Thijn R.
Abstract
Picornaviruses are a leading cause of human and veterinary infections that result in various diseases, including polio and the common cold. As archetypical non-enveloped viruses, their biology has been extensively studied(1). Although a range of different cell-surface receptors are bound by different picornaviruses(2-7), it is unclear whether common host factors are needed for them to reach the cytoplasm. Using genome-wide haploid genetic screens, here we identify the lipid-modifying enzyme PLA2G16 (refs 8-11) as a picornavirus host factor that is required for a previously unknown event in the viral life cycle. We find that PLA2G16 functions early during infection, enabling virion-mediated genome delivery into the cytoplasm, but not in any virion-assigned step, such as cell binding, endosomal trafficking or pore formation. To resolve this paradox, we screened for suppressors of the Delta PLA2G16 phenotype and identified a mechanism previously implicated in the clearance of intracellular bacteria(12). The sensor of this mechanism, galectin-8 (encoded by LGALS8), detects permeated endosomes and marks them for autophagic degradation, whereas PLA2G16 facilitates viral genome translocation and prevents clearance. This study uncovers two competing processes triggered by virus entry: activation of a pore-activated clearance pathway and recruitment of a phospholipase to enable genome release.