A microbially produced AhR ligand promotes a Tph1-driven tolerogenic program in multiple sclerosis

Multiple sclerosis is a debilitating autoimmune disease, characterized by chronic inflammation of the central nervous system. While the significance of the gut microbiome on multiple sclerosis pathogenesis is established, the underlining mechanisms are unknown. We found that serum levels of the microbial postbiotic tryptophan metabolite indole-3-carboxaldehyde (3-IAld) inversely correlated with disease duration in multiple sclerosis patients. Much like the host-derived tryptophan derivative L-Kynurenine, 3-IAld would bind and activate the Aryl hydrocarbon Receptor (AhR), which, in turn, controls endogenous tryptophan catabolic pathways. As a result, in peripheral lymph nodes, microbial 3-IAld, affected mast-cell tryptophan metabolism, forcing mast cells to produce serotonin via Tph1. We thus propose a protective role for AhR-mast-cell activation driven by the microbiome, whereby natural metabolites or postbiotics will have a physiological role in immune homeostasis and may act as therapeutic targets in autoimmune diseases.

Phenotype and oxidative burst of low-density neutrophil subpopulations are altered in common variable immunodeficiency patients

Common variable immunodeficiency disorder (CVID) is the most common form of primary antibody immunodeficiency. Due to low antibody levels, CVID patients receive intravenous or subcutaneous immunoglobulin replacement therapy as treatment. CVID is associated with the chronic activation of granulocytes, including an increased percentage of low-density neutrophils (LDNs). In this study, we examined changes in the percentage of LDNs and the expression of their surface markers in 25 patients with CVID and 27 healthy donors (HD) after in vitro stimulation of whole blood using IVIg. An oxidative burst assay was used to assess the functionality of LDNs. CVID patients had increased both relative and absolute LDN counts with a higher proportion of mLDNs compared to iLDNs, distinguished based on the expression of CD10 and CD16. Immature LDNs in the CVID and HD groups had significantly reduced oxidative burst capacity compared to mature LDNs. Interestingly we observed reduced oxidative burst capacity, reduced expression of CD10 after stimulation of WB, and higher expression of PD-L1 in mature LDNs in CVID patients compared to HD cells. Our data indicate that that the functional characteristics of LDNs are closely linked to their developmental stage. The observed reduction in oxidative burst capacity in mLDNs in CVID patients could contribute to an increased susceptibility to recurrent bacterial infections among CVID patients.

TGF-β induces matrisome pathological alterations and EMT in patient-derived prostate cancer tumoroids

Extracellular matrix (ECM) tumorigenic alterations resulting in high matrix deposition and stiffening are hallmarks of adenocarcinomas and are collectively defined as desmoplasia. Here, we thoroughly analysed primary prostate cancer tissues obtained from numerous patients undergoing radical prostatectomy to highlight reproducible structural changes in the ECM leading to the loss of the glandular architecture. Starting from patient cells, we established prostate cancer tumoroids (PCTs) and demonstrated they require TGF-β signalling pathway activity to preserve phenotypical and structural similarities with the tissue of origin. By modulating TGF-β signalling pathway in PCTs, we unveiled its role in ECM accumulation and remodelling in prostate cancer. We also found that TGF-β-induced ECM remodelling is responsible for the initiation of prostate cell epithelial-to-mesenchymal transition (EMT) and the acquisition of a migratory, invasive phenotype. Our findings highlight the cooperative role of TGF-β signalling and ECM desmoplasia in prompting prostate cell EMT and promoting tumour progression and dissemination.

Expression of circular RNAs in myelodysplastic neoplasms and their association with mutations in the splicing factor gene SF3B1

Mutations in the splicing factor 3b subunit 1 (SF3B1) gene are frequent in myelodysplastic neoplasms (MDS). Because the splicing process is involved in the production of circular RNAs (circRNAs), we investigated the impact of SF3B1 mutations on circRNA processing. Using RNA sequencing, we measured circRNA expression in CD34+ bone marrow MDS cells. We defined circRNAs deregulated in a heterogeneous group of MDS patients and described increased circRNA formation in higher-risk MDS. We showed that the presence of SF3B1 mutations did not affect the global production of circRNAs; however, deregulation of specific circRNAs was observed. Particularly, we demonstrated that strong upregulation of circRNAs processed from the zinc finger E-box binding homeobox 1 (ZEB1) transcription factor; this upregulation was exclusive to SF3B1-mutated patients and was not observed in those with mutations in other splicing factors or other recurrently mutated genes, or with other clinical variables. Furthermore, we focused on the most upregulated ZEB1-circRNA, hsa_circ_0000228, and, by its knockdown, we demonstrated that its expression is related to mitochondrial activity. Using microRNA analyses, we proposed miR-1248 as a direct target of hsa_circ_0000228. To conclude, we demonstrated that mutated SF3B1 leads to deregulation of ZEB1-circRNAs, potentially contributing to the defects in mitochondrial metabolism observed in SF3B1-mutated MDS.

Influence of protein corona on the interaction of glycogen-siRNA constructs with ex vivo human blood immune cells

Glycogen-nucleic acid constructs i.e., glycoplexes are emerging promising platforms for the alteration of gene expression and transcription. Understanding the interaction of glycoplexes with human blood components, such as serum proteins and peripheral blood mononuclear cells (PBMCs), is important to overcome immune cell activation and control biodistribution upon administration of the glycoplexes in vivo. Herein, we investigated the interactions of polyethylene glycol (PEG)ylated and non-PEGylated glycoplexes carrying siRNA molecules with PBMCs isolated from the blood of healthy donors. We found that both types of glycoplexes were non-toxic and were primarily phagocytosed by monocytes without triggering a pro-inflammatory interleukin 6 cytokine production. Furthermore, we investigated the role of the protein corona on controlling the internalization efficiency in immune cells - we found that the adsorption of serum proteins, in particular haptoglobin, alpha-1-antitrypsin and apolipoprotein A-II, onto the non-PEGylated glycoplexes, significantly reduced the uptake of the glycoplexes by PBMCs. Moreover, the non-PEGylated glycoplexes were efficient in the nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) knockdown in monocytic THP-1 cell line. This study provides an insight into the rational design of glycogen-based nanocarriers for the safe delivery of siRNA without eliciting unwanted immune cell activation and efficient siRNA activity upon its delivery.

RUNX1 mutations contribute to the progression of MDS due to disruption of antitumor cellular defense: a study on patients with lower-risk MDS

Patients with lower-risk myelodysplastic syndromes (LR-MDS) have a generally favorable prognosis; however, a small proportion of cases progress rapidly. This study aimed to define molecular biomarkers predictive of LR-MDS progression and to uncover cellular pathways contributing to malignant transformation. The mutational landscape was analyzed in 214 LR-MDS patients, and at least one mutation was detected in 137 patients (64%). Mutated RUNX1 was identified as the main molecular predictor of rapid progression by statistics and machine learning. To study the effect of mutated RUNX1 on pathway regulation, the expression profiles of CD34 + cells from LR-MDS patients with RUNX1 mutations were compared to those from patients without RUNX1 mutations. The data suggest that RUNX1-unmutated LR-MDS cells are protected by DNA damage response (DDR) mechanisms and cellular senescence as an antitumor cellular barrier, while RUNX1 mutations may be one of the triggers of malignant transformation. Dysregulated DDR and cellular senescence were also observed at the functional level by detecting γH2AX expression and β-galactosidase activity. Notably, the expression profiles of RUNX1-mutated LR-MDS resembled those of higher-risk MDS at diagnosis. This study demonstrates that incorporating molecular data improves LR-MDS risk stratification and that mutated RUNX1 is associated with a suppressed defense against LR-MDS progression.

Triggering the nanophase separation of albumin through multivalent binding to glycogen for drug delivery in 2D and 3D multicellular constructs

Engineered nanoparticles for the encapsulation of bioactive agents hold promise to improve disease diagnosis, prevention and therapy. To advance this field and enable clinical translation, the rational design of nanoparticles with controlled functionalities and a robust understanding of nanoparticle-cell interactions in the complex biological milieu are of paramount importance. Herein, a simple platform obtained through the nanocomplexation of glycogen nanoparticles and albumin is introduced for the delivery of chemotherapeutics in complex multicellular 2D and 3D systems. We found that the dendrimer-like structure of aminated glycogen nanoparticles is key to controlling the multivalent coordination and phase separation of albumin molecules to form stable glycogen-albumin nanocomplexes. The pH-responsive glycogen scaffold conferred the nanocomplexes the ability to undergo partial endosomal escape in tumour, stromal and immune cells while albumin enabled nanocomplexes to cross endothelial cells and carry therapeutic agents. Limited interactions of nanocomplexes with T cells, B cells and natural killer cells derived from human blood were observed. The nanocomplexes can accommodate chemotherapeutic drugs and release them in multicellular 2D and 3D constructs. The drugs loaded on the nanocomplexes retained their cytotoxic activity, which is comparable with the activity of the free drugs. Cancer cells were found to be more sensitive to the drugs in the presence of stromal and immune cells. Penetration and cytotoxicity of the drug-loaded nanocomplexes in tumour mimicking tissues were validated using a 3D multicellular-collagen construct in a perfusion bioreactor. The results highlight a simple and potentially scalable strategy for engineering nanocomplexes made entirely of biological macromolecules with potential use for drug delivery.

Modeling Approaches Reveal New Regulatory Networks in Aspergillus fumigatus Metabolism

Systems biology approaches are extensively used to model and reverse-engineer gene regulatory networks from experimental data. Indoleamine 2,3-dioxygenases (IDOs)-belonging in the heme dioxygenase family-degrade l-tryptophan to kynurenines. These enzymes are also responsible for the de novo synthesis of nicotinamide adenine dinucleotide (NAD+). As such, they are expressed by a variety of species, including fungi. Interestingly, Aspergillus may degrade l-tryptophan not only via IDO but also via alternative pathways. Deciphering the molecular interactions regulating tryptophan metabolism is particularly critical for novel drug target discovery designed to control pathogen determinants in invasive infections. Using continuous time Bayesian networks over a time-course gene expression dataset, we inferred the global regulatory network controlling l-tryptophan metabolism. The method unravels a possible novel approach to target fungal virulence factors during infection. Furthermore, this study represents the first application of continuous-time Bayesian networks as a gene network reconstruction method in Aspergillus metabolism. The experiment showed that the applied computational approach may improve the understanding of metabolic networks over traditional pathways.

Roles of IL-2 in bridging adaptive and innate immunity, and as a tool for cellular immunotherapy

IL-2 was initially characterized as a T cell growth factor in the 1970s, and has been studied intensively ever since. Decades of research have revealed multiple and diverse roles for this potent cytokine, indicating a unique linking role between adaptive and innate arms of the immune system. Here, we review the literature showing that IL-2 is expressed in a plethora of cell types across the immune system, where it has indispensable functions in orchestrating cellular interactions and shaping the nature and magnitude of immune responses. Emerging from the basic research that has revealed the molecular mechanisms and the complexity of the biologic actions of IL-2, several immunotherapeutic approaches have now focused on manipulating the levels of this cytokine in patients. These strategies range from inhibition of IL-2 to achieve immunosuppression, to the application of IL-2 as a vaccine adjuvant and in cancer therapies. This review will systematically summarize the major findings in the field and identify key areas requiring further research in order to realize the potential of IL-2 in the treatment of human diseases.

Learning to control tissue damage while fighting Aspergillus

Aspergillus moulds are increasingly being recognised as significant human pathogens that can cause life-threatening infections in the context of host immune dysregulation, particularly in the lung. It is now clear that there is a close relationship between infection susceptibility and the fine regulation of pulmonary immunity and inflammation. While the contribution of IL-17/Th17 responses to both physiological and pathological lung inflammation is now well established, the cellular interactions, soluble factors, and signalling pathways that determine Th17 cell responses to fungal infection remain unclear. Here, we identify potential key mediators of fungus-DC-T cell interactions in the respiratory tract, with a focus on the DC-derived cytokines thought to exert a major influence on generation of pathological Th17 cells. We review recent data indicating a crucial role for Aspergillus-induced autophagy in lung DCs on subsequent T-cell polarization and modulation of 'stemness', which appears critical for avoiding pathological lung inflammation and promoting disease resolution.

The Telomerase Complex Directly Controls Hematopoietic Stem Cell Differentiation and Senescence in an Induced Pluripotent Stem Cell Model of Telomeropathy

Telomeropathies are rare disorders associated with impaired telomere length control mechanisms that frequently result from genetic mutations in the telomerase complex. Dyskeratosis congenita is a congenital progressive telomeropathy in which mutation in the telomerase RNA component (TERC) impairs telomere maintenance leading to accelerated cellular senescence and clinical outcomes resembling premature aging. The most severe clinical feature is perturbed hematopoiesis and bone-marrow failure, but the underlying mechanisms are not fully understood. Here, we developed a model of telomerase function imbalance using shRNA to knockdown TERC expression in human induced pluripotent stem cells (iPSCs). We then promoted in vitro hematopoiesis in these cells to analyze the effects of TERC impairment. Reduced TERC expression impaired hematopoietic stem-cell (HSC) differentiation and increased the expression of cellular senescence markers and production of reactive oxygen species. Interestingly, telomere length was unaffected in shTERC knockdown iPSCs, leading to conclusion that the phenotype is controlled by non-telomeric functions of telomerase. We then assessed the effects of TERC-depletion in THP-1 myeloid cells and again observed reduced hematopoietic and myelopoietic differentiative potential. However, these cells exhibited impaired telomerase activity as verified by accelerated telomere shortening. shTERC-depleted iPSC-derived and THP-1-derived myeloid precursors had lower phagocytic capacity and increased ROS production, indicative of senescence. These findings were confirmed using a BIBR1532 TERT inhibitor, suggesting that these phenotypes are dependent on telomerase function but not directly linked to telomere length. These data provide a better understanding of the molecular processes driving the clinical signs of telomeropathies and identify novel roles of the telomerase complex other than regulating telomere length.

The IL-17F/IL-17RC Axis Promotes Respiratory Allergy in the Proximal Airways

The interleukin 17 (IL-17) cytokine and receptor family is central to antimicrobial resistance and inflammation in the lung. Mice lacking IL-17A, IL-17F, or the IL-17RA subunit were compared with wild-type mice for susceptibility to airway inflammation in models of infection and allergy. Signaling through IL-17RA was required for efficient microbial clearance and prevention of allergy; in the absence of IL-17RA, signaling through IL-17RC on epithelial cells, predominantly by IL-17F, significantly exacerbated lower airway Aspergillus or Pseudomonas infection and allergic airway inflammation. In contrast, following infection with the upper respiratory pathogen Staphylococcus aureus, the IL-17F/IL-17RC axis mediated protection. Thus, IL-17A and IL-17F exert distinct biological effects during pulmonary infection; the IL-17F/IL-17RC signaling axis has the potential to significantly worsen pathogen-associated inflammation of the lower respiratory tract in particular, and should be investigated further as a therapeutic target for treating pathological inflammation in the lung.

Calcineurin-NFAT signalling in myeloid leucocytes: new prospects and pitfalls in immunosuppressive therapy

Myeloid leucocytes mediate host protection against infection and critically regulate inflammatory responses in body tissues. Pattern recognition receptor signalling is crucial for myeloid cell responses to pathogens, but growing evidence suggests an equally potent role for Calcineurin–NFAT signalling in control of myeloid cell function. All major subsets of myeloid leucocytes employ Calcineurin–NFAT signalling during immune responses to pathogens and/or tissue damage, but the influence this pathway exerts on pathogen clearance and host susceptibility to infection is not fully understood. Recent data from experimental models indicate that Calcineurin‐NFAT signalling is essential for infection control, and calcineurin inhibitors used in transplantation medicine (including cyclosporine A and tacrolimus) are now being tested for efficacy in a diverse range of inflammatory conditions and autoimmune pathologies. Efforts to repurpose calcineurin inhibitor drugs for new therapeutic applications may yield rapid improvements in clinical outcomes, but the potential impact of these compounds on myeloid cell function in treated patients is largely unknown. Here we discuss Calcineurin–NFAT control of myeloid leucocyte function in the context of recent therapeutic developments and ongoing clinical studies.

Leucine-Rich Repeat Kinase 2 Controls the Ca2+/Nuclear Factor of Activated T Cells/IL-2 Pathway during Aspergillus Non-Canonical Autophagy in Dendritic Cells

The Parkinson's disease-associated protein, Leucine-rich repeat kinase 2 (LRRK2), a known negative regulator of nuclear factor of activated T cells (NFAT), is expressed in myeloid cells such as macrophages and dendritic cells (DCs) and is involved in the host immune response against pathogens. Since, the Ca²⁺/NFAT/IL-2 axis has been previously found to regulate DC response to the fungus Aspergillus, we have investigated the role played by the kinase LRRK2 during fungal infection. Mechanistically, we found that in the early stages of the non-canonical autophagic response of DCs to the germinated spores of Aspergillus, LRRK2 undergoes progressive degradation and regulates NFAT translocation from the cytoplasm to the nucleus. Our results shed new light on the complexity of the Ca²⁺/NFAT/IL-2 pathway, where LRRK2 plays a role in controlling the immune response of DCs to Aspergillus.

High-Throughput Screening of Senescence Markers in Hematopoietic Stem Cells Derived from Induced Pluripotent Stem Cells

The successful development and characterization of human induced pluripotent stem cells (iPSCs) provides a powerful tool to study the molecular mechanisms that control cell fate decisions and differentiation toward distinct lineages. Here we focus on the ability of donors derived iPSCs to differentiate toward hematopoietic progenitor cells and on the analysis of their telomere length. The ability to screen telomere length in individual donors is important for defining cellular senescence, which correlates with their differentiation potential toward hematopoietic lineages. We have modified iPSC culture protocol and telomere length analysis to suit for high throughput screening of telomere length in large number of individual donors. This approach can be used to demonstrate the heterogeneity or changes of telomere length and its shortening as an exclusion criterion for selection of suitable donors for future stem cell therapies.

Chronic Inflammation in Immune Aging: Role of Pattern Recognition Receptor Crosstalk with the Telomere Complex?

Age-related decline in immunity is characterized by stem cell exhaustion, telomere shortening, and disruption of cell-to-cell communication, leading to increased patient risk of disease. Recent data have demonstrated that chronic inflammation exerts a strong influence on immune aging and is closely correlated with telomere length in a range of major pathologies. The current review discusses the impact of inflammation on immune aging, the likely molecular mediators of this process, and the various disease states that have been linked with immunosenescence. Emerging findings implicate NF-κB, the major driver of inflammatory signaling, in several processes that regulate telomere maintenance and/or telomerase activity. While prolonged triggering of pattern recognition receptors is now known to promote immunosenescence, it remains unclear how this process is linked with the telomere complex or telomerase activity. Indeed, enzymatic control of telomere length has been studied for many decades, but alternative roles of telomerase and potential influences on inflammatory responses are only now beginning to emerge. Crosstalk between these pathways may prove to be a key molecular mechanism of immunosenescence. Understanding how components of immune aging interact and modify host protection against pathogens and tumors will be essential for the design of new vaccines and therapies for a wide range of clinical scenarios.

Impaired calcineurin signaling in myeloid cells results in downregulation of pentraxin-3 and increased susceptibility to aspergillosis

Treatment of post-transplant patients with immunosuppressive drugs targeting the calcineurin-nuclear factor of activated T cells (NFAT) pathway, including cyclosporine A or tacrolimus, is commonly associated with a higher incidence of opportunistic infections, such as Aspergillus fumigatus, which can lead to severe life-threatening conditions. A component of the A. fumigatus cell wall, β-glucan, is recognized by dendritic cells (DCs) via the Dectin-1 receptor, triggering downstream signaling that leads to calcineurin-NFAT binding, NFAT translocation, and transcription of NFAT-regulated genes. Here, we address the question of whether calcineurin signaling in CD11c-expressing cells, such as DCs, has a specific role in the innate control of A. fumigatus. Impairment of calcineurin in CD11c-expressing cells (CD11c^crecnb1^loxP) significantly increased susceptibility to systemic A. fumigatus infection and to intranasal infection in irradiated mice undergoing bone marrow transplant. Global expression profiling of bone marrow-derived DCs identified calcineurin-regulated processes in the immune response to infection, including expression of pentraxin-3, an important antifungal defense protein. These results suggest that calcineurin inhibition directly impairs important immunoprotective functions of myeloid cells, as shown by the higher susceptibility of CD11c^crecnb^loxP mice in models of systemic and invasive pulmonary aspergillosis, including after allogeneic bone marrow transplantation. These findings are relevant to the clinical management of transplant patients with severe Aspergillus infections.

Calcium and calcineurin-NFAT signaling regulate granulocyte-monocyte progenitor cell cycle via Flt3-L

Maintenance of myeloid progenitor cells is controlled by complex regulatory mechanisms and is orchestrated by multiple different transcription factors. Here, we report that the activation of the transcription factor nuclear factor of activated T cells (NFAT) by calcium-sensing protein calcineurin inhibits the proliferation of myeloid granulocyte–monocyte progenitors (GMPs). Myeloid progenitor subtypes exhibit variable sensitivity to induced Ca²⁺ entry and consequently display differential engagement of the calcineurin-NFAT pathway. This study shows that inhibition of the calcineurin-NFAT pathway enhances the proliferation of GMPs both in vitro and in vivo and demonstrates that calcineurin-NFAT signaling in GMPs is initiated by Flt3-L. Inhibition of the calcineurin-NFAT pathway modified expression of the cell cycle regulation genes Cdk4, Cdk6, and Cdkn1a (p21), thus enabling rapid cell cycle progression specifically in GMPs. NFAT inhibitor drugs are extensively used in the clinic to restrict the pathological activation of lymphoid cells, and our data reveal for the first time that these therapies also exert potent effects on maintenance of the myeloid cell compartment through specific regulation of GMP proliferation. Stem Cells2014;32:3232–3244

Use of human monoclonal antibodies to treat Chikungunya virus infection

Chikungunya virus (CHIKV) is an alphavirus prevalent in tropical regions. It causes an acute febrile disease that, in elderly individuals and newborns, is often associated with severe complications. We previously reported the isolation and characterization of 2 human monoclonal antibodies neutralizing CHIKV in vitro: 5F10 and 8B10. Here, we tested their efficacy in vivo as prophylactic and therapeutic treatments of CHIKV infection in AGR129 mice. In both settings, 5F10 and 8B10 were able to significantly delay CHIKV-driven lethality. Our results support the development of prophylactic and therapeutic treatments for CHIKV infection, using a combination of 5F10 and 8B10.

Interleukin-2 production by dendritic cells and its immuno-regulatory functions

Dendritic cells (DCs) are uniquely potent antigen presenting cells that acquire microbial products and prime adaptive immune responses against pathogens. Furthermore, DCs also play a key role in induction and maintenance of tolerance. Although numerous studies have assessed the diverse functions of DCs, many unanswered questions remain regarding the molecular mechanisms that DCs use to achieve immunoregulation. While not widely regarded as a significant provider of T-cell growth factors, DCs have previously been identified as a potential source of IL-2 cytokine. Recent research indicates that microbes are the most effective stimuli to trigger IL-2 production in DCs by activating the calcineurin/NFAT signaling pathway. Herein we describe recent insights into the production and function of IL-2 cytokine and IL-2 receptor in DCs early after stimulation through pattern recognition receptors. These findings clarify how DCs fine-tune effector and regulatory responses by modulating IL-2 production in both tolerance and immunity.

Calcineurin/NFAT signalling inhibits myeloid haematopoiesis

Nuclear factor of activated T cells (NFAT) comprises a family of transcription factors that regulate T cell development, activation and differentiation. NFAT signalling can also mediate granulocyte and dendritic cell (DC) activation, but it is unknown whether NFAT influences their development from progenitors. Here, we report a novel role for calcineurin/NFAT signalling as a negative regulator of myeloid haematopoiesis. Reconstituting lethally irradiated mice with haematopoietic stem cells expressing an NFAT-inhibitory peptide resulted in enhanced development of the myeloid compartment. Culturing bone marrow cells in media supplemented with Flt3-L in the presence of the calcineurin/NFAT inhibitor Cyclosporin A increased numbers of differentiated DC. Global gene expression analysis of untreated DC and NFAT-inhibited DC revealed differential expression of transcripts that regulate cell cycle and apoptosis. In conclusion, these results provide evidence that calcineurin/NFAT signalling negatively regulates myeloid lineage development. The finding that inhibition of NFAT enhances myeloid development provides a novel insight into understanding how the treatment with drugs targeting calcineurin/NFAT signalling influence the homeostasis of the innate immune system.

Optical and Electrical Properties of Undoped Microcrystalline Silicon Deposited by the VHF-GD with Different Dilutions of Silane in Hydrogen

We show that the optical and electrical properties of microcrystalline silicon (μc-Si:H) deposited by the VHF-GD technique at 110 MHz can considerably be tuned by changing the dilution ratio of silane to hydrogen.

With increasing silane dilution we observe enhanced optical absorption for energies below 2 eV due to the transition of the material from amorphous / microcrystalline mixture to a pure microcrystalline phase. Simultaneously, the light scattering and the defect absorption increases. Strong dilution also promotes the incorporation of impurities into the material, leading to a pronounced extrinsic behaviour as seen from the decrease of the activiation energy of the electrical conductivity.

The electrical properties were investigated in the dark by the Time of Flight technique. We measured drift mobilities at room temperature which slightly increase with dilution, reaching values of 3 cm2/Vs for electrons and 1.2 cm2/Vs for holes. The ratio between electron and hole drift mobilities is found to be around 2 for all samples studied, similar to that of crystalline silicon.

Furthermore, post-transient Time of Flight measurements revealed detrimental electron deep traps in low dilution material.

Bcr-Abl fusion sequences do not induce immune responses in mice when administered in mouse polyomavirus based virus-like particles

Mouse polyomavirus-like particles (MPyV-VLPs) carrying inside a fragment of the Bcr-Abl hybrid protein containing the epitope of chronic myeloid leukemia fusion region were prepared. A sequence encoding 171 amino acids covering Bcr-Abl breakpoint was fused to the C-terminal part of VP3 minor protein connecting it to the VP1 capsomeres. Chimeric particles, the Bcr-Abl VLPs, were tested for their ability to induce Bcr-Abl specific immune response in mice after their intranasal (i.n.) or intraperitoneal (i.p.) administration without any other adjuvants. Bcr-Abl VLPs induced strong anti-VP1 immune response in both i.n. and i.p. immunized mice. As expected, neither IgG nor IgM anti-Bcr-Abl specific antibodies were detected in the sera of immunized animals. Surprisingly, no specific CTL (cytotoxic T-lymphocyte) activity was proved using two different methods (in vitro cytotoxicity assay with CFSE-labeled target cells and highly sensitive cytotoxicity assay using MHC class I Bcr-Abl specific pentamers). In addition, no proliferative response of T-cells of i.n. immunized mice after in vitro restimulation with antigen-pulsed bone marrow-derived dendritic cells was observed. Taken together, Bcr-Abl breakpoint epitopes appeared to be weak immunogens and even MPyV-VLPs did not provide sufficient adjuvant ability to support induction of immune responses specific to Bcr-Abl fusion zone epitope.

Distinct regulatory roles of transforming growth factor-beta and interleukin-4 in the development and maintenance of natural and induced CD4+ CD25+ Foxp3+ regulatory T cells

The development and function of CD4(+) CD25(+) Foxp3(+) regulatory T cells (Tregs) are strictly regulated by cytokines. Here we show that transforming growth factor-beta (TGF-beta) and interleukin-4 (IL-4) play a crucial and antagonistic role in the development of Tregs. Additionally, these cytokines also have distinct effects on the maintenance of natural (nTregs) and antigen-induced (iTregs) Tregs. Using double-staining and tracking of proliferation of purified and carboxyflourescein succinimidyl ester (CFSE)-labelled mouse T-cell subpopulations we demonstrated that CD4(+) CD25(+) Foxp3(+) iTregs develop upon alloantigenic stimulation in the presence of TGF-beta exclusively from CD4(+) CD25(-) Foxp3(-) precursors. Both the induction of Foxp3 expression and Treg proliferation were prevented when the cells were stimulated in the presence of IL-4. By contrast, nTregs did not proliferate in the presence of the antigen and TGF-beta, and partially lost their Foxp3 expression. IL-4 not only prevented the development of iTregs, but also down-regulated the level of Foxp3 mRNA and decreased the number of Foxp3(+) cells in a population of iTregs. Further analyses proved that IL-4 decreased the expression of Foxp3 only in a population of iTregs, whereas it substantially supported the survival of nTregs. Functional experiments showed that Tregs induced in the presence of alloantigen and TGF-beta inhibited, on a per-cell basis, cell proliferation comparably to nTregs, and their suppressive capacity was not modulated by IL-4. These data suggest that TGF-beta and IL-4 differentially regulate the development of Tregs and distinctly sustain Foxp3 expression and the number of nTregs and iTregs, but have no influence on the suppressive activity of Tregs on a per-cell basis.

A rapid separation of two distinct populations of mouse corneal epithelial cells with limbal stem cell characteristics by centrifugation on percoll gradient

PURPOSE

To detect and isolate cells with stem cell (SC) characteristics in the limbus of the mouse.

METHODS

Limbal tissues from BALB/c mice were trypsin-dissociated and separated on the gradient Percoll (Fluka, Buchs, Switzerland). Several fractions were isolated and characterized by real-time PCR for the presence of limbal SC markers and differentiation markers of corneal epithelial cells by flow cytometry for the determination of the side-population (SP) phenotype and growth properties in vitro.

RESULTS

Cells retained in the lightest fraction (40% Percoll) and in the densest fraction (80% Percoll) of the gradient were both enriched for populations with a high expression of the SC markers ABCG2 and Lgr5 and also expressing the SP phenotype. However, the lightest fraction (representing approximately 12% of total limbal cells) contained cells with the strongest spontaneous proliferative capacity and expressed the corneal epithelial differentiation marker K12. In contrast the densest fraction (<7% of original cells) was K12 negative and contained small nonspontaneously proliferating cells, which instead were positive for p63. Unexpectedly, cells from this fraction had the highest proliferative activity when cultured on a 3T3 feeder cell monolayer.

CONCLUSIONS

These findings demonstrate the presence of two distinct populations of corneal epithelial cells with limbal SC characteristics, based on differential expression of the keratin-specific marker K12 and transcription factor p63, and suggest a difference in developmental stage of the two populations, with the K12(-)p63(+) population being closer to the primitive limbal SC.

Cellular and humoral immune responses to chimeric EGFP-pseudocapsids derived from the mouse polyomavirus after their intranasal administration

Mouse polyomavirus (MPyV) VP1-pseudocapsids carrying enhanced green fluorescent protein (EGFP-VLPs) were used for intranasal immunization of mice. EGFP-VLPs induced strong anti-VP1 but not anti-EGFP antibody production. In vitro restimulation with antigen-pulsed bone marrow-derived dendritic cells (BMDCs) induced remarkable T-cell proliferative response specific for both VP1 and EGFP antigen and IL-2 and IFN-gamma production. Surprisingly, no specific cytotoxic activities against VP1 and EGFP proteins were detected. After intranasal administration of EGFP-VLPs, as well as after polyomavirus infection, a moderate reduction of CD4(+)CD25(+)Foxp3(+) T cells was observed in spleens but not in lymph nodes and peripheral blood, suggesting that both MPyV virions and pseudocapsids are able to induce changes in distribution of regulatory T cells. Treatment of EGFP-VLPs pulsed BMDCs with inhibitors of endosomal acidification proved that presentation of peptides on MHCgp class II is dependent on acidic endosomal environment. Substantial decrease of CD4-specific T-cell proliferation in the presence of proteasome inhibitor suggests that MHCgp class II might load VPL-derived peptides processed by proteasomes. Thus, polyomavirus derived VLPs appear to be promising delivery and adjuvant vehicles for therapeutic proteins.

Depletion of T(reg) cells inhibits minimal residual disease after surgery of HPV16-associated tumours

It is generally accepted that T regulatory cells (T(reg) CD4(+)CD25(+)Foxp3(+)) play an important role in the suppression of tumour immunity. We examined the impact of T(reg) cell depletion with anti-CD25 antibody as adjuvant therapy in the treatment of minimal residual disease after excision of murine HPV16-associated tumours. We found that the depletion of T(reg) cells inhibited growth of the recurrences after surgery of HPV16-associated MHC class I+ as well as MHC class I-deficient tumours transplanted in syngeneic mice. These results demonstrate that depletion of CD25(+)CD4(+) T(reg) cells can be used as an efficient adjuvant treatment improving the results of surgery in the experimental systems mimicking human MHC class I+ and MHC class I-deficient, HPV16-associated neoplasms. Therefore, this therapeutic modality is worth being examined in patients with minimal residual HPV16-associated tumour disease after surgery.

Production of nitric oxide during graft rejection is regulated by the Th1/Th2 balance, the arginase activity, and L-arginine metabolism

BACKGROUND

Production of nitric oxide (NO) by graft infiltrating macrophages has been proposed as an important effector mechanism of allograft rejection. Although high levels of NO are generated during allograft rejection, undetectable or only limited amounts of NO were found in rejected skin xenografts.

METHODS

BALB/c mice were grafted with skin transplants from syngeneic, allogeneic or xenogeneic (rat) donors. The production of NO, cytokines and arginase in the grafts was determined by spectrophotometry, enzyme-linked immunosorbent assay, or polymerase chain reaction. Effects of depletion of CD4+ cells, neutralization of interleukin (IL)-4 or application of arginase inhibitors N(omega)-hydroxy-L-arginine (L-NOHA) and L-valine on production of NO in rejected xenografts were evaluated.

RESULTS

Rejection of rat skin xenografts, on the contrary to rejection of allografts, was associated with a local high production of Th2 cytokines IL-4 and IL-10, overexpression of arginase genes, strongly enhanced arginase activity and attenuated NO generation in the graft. The supernatants obtained after cultivation of skin xenograft (but not allograft or syngeneic graft) explants contained a high arginase activity and strongly suppressed NO production by activated macrophages. This suppression was completely inhibited by L-NOHA or was overcome by an excess of exogenous L-arginine, a substrate for NO synthesis. Cocultivation of xenograft explants that did not produce NO with arginase inhibitors L-NOHA or L-valine restored NO generation in the graft.

CONCLUSION

The results suggest that upregulation of arginase activity by Th2 cytokines during xenograft rejection limits the bioavailability of L-arginine for the inducible NO synthase and thus attenuates generation of NO by the graft-infiltrating macrophages.

Polyomavirus EGFP-pseudocapsids: Analysis of model particles for introduction of proteins and peptides into mammalian cells

A vector for preparation of mouse polyomavirus capsid-like particles for transfer of foreign peptides or proteins into cells was constructed. Model pseudocapsids carrying EGFP fused with the C-terminal part of the VP3 minor protein (EGFP-VLPs) have been prepared and analysed for their ability to be internalised and processed by mouse cells and to activate mouse and human dendritic cells (DC) in vitro. EGFP-VLPs entered mouse epithelial cells, fibroblasts and human and mouse DC efficiently and were processed by both, lysosomes and proteasomes. Surprisingly, they did not induce upregulation of DC co-stimulation molecules or maturation markers in vitro; however, they did induce interleukin 12 secretion.

PML-RARA-targeted DNA vaccine induces protective immunity in a mouse model of leukemia

Despite improved molecular characterization of malignancies and development of targeted therapies, acute leukemia is not curable and few patients survive more than 10 years after diagnosis. Recently, combinations of different therapeutic strategies (based on mechanisms of apoptosis, differentiation and cytotoxicity) have significantly increased survival. To further improve outcome, we studied the potential efficacy of boosting the patient's immune response using specific immunotherapy. In an animal model of acute promyelocytic leukemia, we developed a DNA-based vaccine by fusing the human promyelocytic leukemia-retinoic acid receptor-alpha (PML-RARA) oncogene to tetanus fragment C (FrC) sequences. We show for the first time that a DNA vaccine specifically targeted to an oncoprotein can have a pronounced effect on survival, both alone and when combined with all-trans retinoic acid (ATRA). The survival advantage is concomitant with time-dependent antibody production and an increase in interferon-gamma (IFN-gamma). We also show that ATRA therapy on its own triggers an immune response in this model. When DNA vaccination and conventional ATRA therapy are combined, they induce protective immune responses against leukemia progression in mice and may provide a new approach to improve clinical outcome in human leukemia.

Alloantigen-induced, T-cell-dependent production of nitric oxide by macrophages infiltrating skin allografts in mice

The immunological rejection reaction occurring after organ or tissue transplantation is characterized by a strong infiltration of the graft by T cells and macrophages. Since the rejection reaction is highly specific, we tested the role of T cells in the activation of macrophages and in the induction of nitric oxide (NO) production during graft rejection. The rejection of both MHC and non-MHC antigen-disparate skin allografts was associated with a significantly increased production of NO in the graft. The kinetics of NO production after transplantation correlated with the rejection reaction and with the fate of the allograft. A significant reduction in NO production was found in immunologically hyporeactive mice treated with cyclosporine, and no specific production of NO was found in tolerated skin allografts from neonatally tolerant mice. The production of NO was completely suppressed in graft explants from mice with depleted CD4(+) cells, but remained at a normal level in skin allografts from mice treated with anti-CD8 monoclonal antibody. The treatment of recipients of fully allogeneic skin grafts with 2-amino-5,6-dihydro-6-methyl-4H-1,3-thiazine (AMT), a specific inhibitor of the inducible NO synthase, resulted in a significant prolongation of graft survival. The results thus show CD4(+) T-cell-dependent, alloantigen-induced production of NO by graft-infiltrating macrophages and the role of NO in the rejection reaction. We suggest that this pathway may represent one of the local effector mechanisms of graft rejection.

Alloantigen-induced, T-cell-dependent production of nitric oxide by macrophages infiltrating skin allografts in mice

The immunological rejection reaction occurring after organ or tissue transplantation is characterized by a strong infiltration of the graft by T cells and macrophages. Since the rejection reaction is highly specific, we tested the role of T cells in the activation of macrophages and in the induction of nitric oxide (NO) production during graft rejection. The rejection of both MHC and non-MHC antigen-disparate skin allografts was associated with a significantly increased production of NO in the graft. The kinetics of NO production after transplantation correlated with the rejection reaction and with the fate of the allograft. A significant reduction in NO production was found in immunologically hyporeactive mice treated with cyclosporine, and no specific production of NO was found in tolerated skin allografts from neonatally tolerant mice. The production of NO was completely suppressed in graft explants from mice with depleted CD4(+) cells, but remained at a normal level in skin allografts from mice treated with anti-CD8 monoclonal antibody. The treatment of recipients of fully allogeneic skin grafts with 2-amino-5,6-dihydro-6-methyl-4H-1,3-thiazine (AMT), a specific inhibitor of the inducible NO synthase, resulted in a significant prolongation of graft survival. The results thus show CD4(+) T-cell-dependent, alloantigen-induced production of NO by graft-infiltrating macrophages and the role of NO in the rejection reaction. We suggest that this pathway may represent one of the local effector mechanisms of graft rejection.

Prospective study of nosocomial fungal meningitis in children--report of 10 cases

Within an 8-year period, 10 cases of fungal nosocomial meningitis in children 0-13 y old were prospectively identified, 3 caused by yeasts other than Candida spp. (Rhodotorula rubra, Aureobasidium mansoni, Clavispora lusitaniae) and 7 by Candida albicans. Seven patients survived. whereas 3 neonates with fungal meningitis (all due to C. albicans) died. Risk factors for fungal nosocomial meningitis included cancer (2 children), previous neurosurgery (2 children), cranial trauma (1 case) and prematurity with low birthweight (5 cases). All patients except 1 had received broad-spectrum antibiotics before onset of meningitis. In addition to yeasts, bacteria were isolated from CSF of 4 children. One child had additional fungaemia. Univariate analysis was used to compare 10 cases of fungal to 91 cases of bacterial nosocomial meningitis. Except for concurrent bacteraemia, (60 vs 25.3%, P < 0.03), which was more frequently observed among fungal meningitis, there were no significant differences in risk factors, sequelae or outcome (mortality) between patients with fungal vs bacterial meningitis. A review of fungal meningitis reported within the last 20 y is included.

Phenotype, immunological reactivity and cytokine production profile of Peyer's patch cells from mice immunized orally with allogeneic cells

Mice of inbred strain BALB/c were immunized orally for 10 consecutive days with fresh spleen cells from allogeneic C57BL/10 (B10) donors. The immunized mice displayed significant allotransplantation immunity in vivo as demonstrated by resistance to the growth of allogeneic tumours induced by high doses of tumour cells. No significant changes in the proportion of the major T cell subsets in PP of immunized mice were found 1 or 7 days after the last immunization dose. However, PP cells from orally immunized mice displayed stronger proliferative response after stimulation with cells used for oral immunization than the cells from control animals. Similarly, after stimulation in vitro with specific alloantigens, PP cells from orally immunized mice produced more IFN-gamma than the cells from control recipients. On the contrary, the production of IL-4 was significantly decreased in the immunized mice. The production of IL-2 by PP cells after oral immunization was not significantly changed and IL-10 was only slightly increased. The results thus show that oral immunization with allogeneic cells induces systemic transplantation immunity which can be demonstrated already in Peyer's patches by increased cell proliferation after immunization with specific alloantigens and by changes in cytokine production.

Induction of specific transplantation immunity by oral immunization with allogeneic cells

Oral administration of antigen has been shown to be effective for both positive and negative modulation of immune responses. In the present study we characterized changes in the reactivity of the immune system after oral immunization with allogeneic spleen cells. Mice were orally immunized for 10 consecutive days with fresh allogeneic spleen cells, and the phenotype, proliferative response, cytotoxic activity and cytokine production profile of recipient spleen cells were assessed 1 or 7 days after the last immunization dose. Although no significant changes in the proportion of CD4+, CD8+ or CD25+ cells were observed in the spleen of orally immunized mice, significant activation of alloreactivity in spleen cells was found. Cells from orally immunized mice exhibited enhanced proliferation and cytotoxic activity after stimulation with specific allogeneic cells in vitro, and produced considerably higher concentrations of interferon-gamma (IFN-gamma) and significantly less interleukin (IL)-4 than did cells from control mice. The production of IL-2 was essentially unchanged and that of IL-10 was only slightly increased. The systemic allosensitization induced by oral immunization was demonstrated in vivo by increased resistance to the growth of allogeneic tumours induced by subcutaneous inoculation of high doses of tumour cells. In addition, orthotopic corneal allografts in orally immunized recipients were rejected more rapidly (in a second-set manner) than in control, untreated recipients. These data show that oral immunization with allogeneic cells modulates individual components of the immune response and that specific transplantation immunity, rather than tolerance, is induced in the treated recipients.

Reproducibility of post-exercise lactate and anaerobic threshold

To test the effect of previous strenuous training on lactate (LA) formation and on changes of lactate threshold (AT) values, a group of seven male athletes aged 26.3 +/- 9.2 years, height 184 +/- 6.2 cm, body weight 79.3 +/- 8.1 kg, percentage of body fat 8.8 +/- 3.7 and VO2 max 56.2 +/- 5.4 ml/kg were examined on a treadmill to the maximum in the morning after 2 days of rest, and after 2 consecutive days of strenuous training. The subjectively perceived rate of fatigue (SPF) in the morning prior to the exercise test was assessed by means of a 5-grade score. The values of LA max, AT, and SPF on day 1 were 11.06 +/- 2.4 mmol/l, 3.5 +/- 0.4 m/s, and 0.6 +/- 0.4, respectively. The corresponding values on day 2 were 8.8 +/- 1.7 mmol/l, 4.0 +/- 0.3 m/s, and 2.0 +/- 0.5, respectively. The values on day 3 were 8.6 +/- 1.1 mmol/l, 4.1 +/- 0.4 m/s, and 2.1 +/- 0.7, respectively. Statistically significant differences on the 1st day were found in LA max, AT, and SPF compared with days 2 and 3. No significant differences were found between the values for the 2nd and 3rd days. AT values for day 1 were significantly lower than those for days 2 and 3. A significantly higher level of SPF in the morning prior to the test procedure was observed on days 2 and 3 compared with day 1. The AT and SPF values for days 2 and 3 showed no significant difference.(ABSTRACT TRUNCATED AT 250 WORDS)