Cutting Edge: Polycomb Repressive Complex 1 Subunit Cbx4 Positively Regulates Effector Responses in CD8 T Cells.

CTL differentiation is controlled by the crosstalk of various transcription factors and epigenetic modulators. Uncovering this process is fundamental to improving immunotherapy and designing novel therapeutic approaches. In this study, we show that polycomb repressive complex 1 subunit chromobox (Cbx)4 favors effector CTL differentiation in a murine model. Cbx4 deficiency in CTLs induced a transcriptional signature of memory cells and increased the memory CTL population during acute viral infection. It has previously been shown that besides binding to H3K27me3 through its chromodomain, Cbx4 functions as a small ubiquitin-like modifier (SUMO) E3 ligase in a SUMO-interacting motifs (SIM)-dependent way. Overexpression of Cbx4 mutants in distinct domains showed that this protein regulates CTL differentiation primarily in an SIM-dependent way and partially through its chromodomain. Our data suggest a novel role of a polycomb group protein Cbx4 controlling CTL differentiation and indicated SUMOylation as a key molecular mechanism connected to chromatin modification in this process.

Epigenetic regulation of T cells by Polycomb group proteins.

T cells are critical for pathogen elimination, tumor surveillance, and immunoregulation. The development, activation, and differentiation of CD8 and CD4 T lymphocytes are a set of complex and dynamically regulated events that require epigenetic control. The Polycomb group (PcG) proteins are a family of diverse and evolutionarily conserved epigenetic modulators fundamentally involved in several mechanisms of gene regulation. PcG proteins can assemble into distinct repressor complexes, the two most understood being the Polycomb Repressor Complex (PRC)1 and PRC2, which control chromatin structure mainly through posttranslational modifications of histones. In this review, we will summarize the most recent findings regarding the diverse roles performed by PcG proteins in T cell biology. We will focus on PRC1 and PRC2 contribution to the regulation of T cell development in the thymus, CD4 T cell differentiation in helper or regulatory phenotypes and CD8 T cell fate commitment in the context of infections and cancer, highlighting the known mechanisms and knowledge gaps that still need to be addressed.

Cytotoxic CD4+ T cells driven by T-cell intrinsic IL-18R/MyD88 signaling predominantly infiltrate Trypanosoma cruzi-infected hearts.

Increasing attention has been directed to cytotoxic CD4+ T cells (CD4CTLs) in different pathologies, both in humans and mice. The impact of CD4CTLs in immunity and the mechanisms controlling their generation, however, remain poorly understood. Here, we show that CD4CTLs abundantly differentiate during mouse infection with the intracellular parasite Trypanosoma cruzi. CD4CTLs display parallel kinetics to Th1 cells in the spleen, mediate specific cytotoxicity against cells presenting pathogen-derived antigens and express immunoregulatory and/or exhaustion markers. We demonstrate that CD4CTL absolute numbers and activity are severely reduced in both Myd88-/- and Il18ra-/- mice. Of note, the infection of mixed-bone marrow chimeras revealed that wild-type (WT) but not Myd88-/- cells transcribe the CD4CTL gene signature and that Il18ra-/- and Myd88-/- CD4+ T cells phenocopy each other. Moreover, adoptive transfer of WT CD4+GzB+ T cells to infected Il18ra-/- mice extended their survival. Importantly, cells expressing the CD4CTL phenotype predominate among CD4+ T cells infiltrating the infected mouse cardiac tissue and are increased in the blood of Chagas patients, in which the frequency of CD4CTLs correlates with the severity of cardiomyopathy. Our findings describe CD4CTLs as a major player in immunity to a relevant human pathogen and disclose T-cell intrinsic IL-18R/MyD88 signaling as a key pathway controlling the magnitude of the CD4CTL response.

Dopamine signaling impairs ROS modulation by mitochondrial hexokinase in human neural progenitor cells.

Dopamine signaling has numerous roles during brain development. In addition, alterations in dopamine signaling may be also involved in the pathophysiology of psychiatric disorders. Neurodevelopment is modulated in multiple steps by reactive oxygen species (ROS), byproducts of oxidative metabolism that are signaling factors involved in proliferation, differentiation, and migration. Hexokinase (HK), when associated with the mitochondria (mt-HK), is a potent modulator of the generation of mitochondrial ROS in the brain. In the present study, we investigated whether dopamine could affect both the activity and redox function of mt-HK in human neural progenitor cells (NPCs). We found that dopamine signaling via D1R decreases mt-HK activity and impairs ROS modulation, which is followed by an expressive release of H2O2 and impairment in calcium handling by the mitochondria. Nevertheless, mitochondrial respiration is not affected, suggesting specificity for dopamine on mt-HK function. In neural stem cells (NSCs) derived from induced-pluripotent stem cells (iPSCs) of schizophrenia patients, mt-HK is unable to decrease mitochondrial ROS, in contrast with NSCs derived from healthy individuals. Our data point to mitochondrial hexokinase as a novel target of dopaminergic signaling, as well as a redox modulator in human neural progenitor cells, which may be relevant to the pathophysiology of neurodevelopmental disorders such as schizophrenia.

Ostreopsis cf. ovata (Dinophyceae) Molecular Phylogeny, Morphology, and Detection of Ovatoxins in Strains and Field Samples from Brazil.

: Recurrent blooms of Ostreopsis cf. ovata have been reported in Brazil and the Mediterranean Sea with associated ecological, and in the latter case, health impacts. Molecular data based on the D1-D3 and D8-D10 regions of the LSU rDNA and ITS loci, and the morphology of O. cf. ovata isolates and field populations from locations along the Brazilian tropical and subtropical coastal regions and three oceanic islands are presented. Additional ITS sequences from three single cells from the tropical coast are provided. Toxin profiles and quantities of PLTX and their analogues; OVTXs; contained in cells from two clonal cultures and two field blooms from Rio de Janeiro were investigated. Morphology was examined using both light and epifluorescence microscopy. Morphometric analysis of different strains and field populations from diverse locations were compared. Molecular analysis showed that six of the seven sequences grouped at the large "Atlantic/Mediterranean/Pacific" sub-clade, while one sequence branched in a sister clade with sequences from Madeira Island and Greece. The toxin profile of strains and bloom field samples from Rio de Janeiro were dominated by OVTX-a and -b, with total cell quotas (31.3 and 39.3 pg cell-1) in the range of that previously reported for strains of O. cf. ovata.

Vaccination With Recombinant Filamentous fd Phages Against Parasite Infection Requires TLR9 Expression.

Recombinant filamentous fd bacteriophages (rfd) expressing antigenic peptides were shown to induce cell-mediated immune responses in the absence of added adjuvant, being a promising delivery system for vaccination. Here, we tested the capacity of rfd phages to protect against infection with the human protozoan Trypanosoma cruzi, the etiologic agent of Chagas Disease. For this, C57BL/6 (B6) and Tlr9-/- mice were vaccinated with rfd phages expressing the OVA257-264 peptide or the T. cruzi-immunodominant peptides PA8 and TSKB20 and challenged with either the T. cruzi Y-OVA or Y-strain, respectively. We found that vaccination with rfd phages induces anti-PA8 and anti-TSKB20 IgG production, expansion of Ag-specific IFN-γ, TNF-α, and Granzyme B-producing CD8+ T cells, as well as in vivo Ag-specific cytotoxic responses. Moreover, the fd-TSKB20 vaccine was able to protect against mortality induced by a high-dose inoculum of the parasite. Although vaccination with rfd phages successfully reduced both parasitemia and parasite load in the myocardium of WT B6 mice, Tlr9-/- animals were not protected against infection. Thus, our data extend previous studies, demonstrating that rfd phages induce Ag-specific IgG and CD8+ T cell-mediated responses and confer protection against an important human parasite infection, through a TLR9-dependent mechanism.