Updates on radiotherapy-immunotherapy combinations: Proceedings of 6th annual ImmunoRad conference.

Focal radiation therapy (RT) has attracted considerable attention as a combinatorial partner for immunotherapy (IT), largely reflecting a well-defined, predictable safety profile and at least some potential for immunostimulation. However, only a few RT-IT combinations have been tested successfully in patients with cancer, highlighting the urgent need for an improved understanding of the interaction between RT and IT in both preclinical and clinical scenarios. Every year since 2016, ImmunoRad gathers experts working at the interface between RT and IT to provide a forum for education and discussion, with the ultimate goal of fostering progress in the field at both preclinical and clinical levels. Here, we summarize the key concepts and findings presented at the Sixth Annual ImmunoRad conference

The Nutritional Induction of COUP-TFII Gene Expression in Ventromedial Hypothalamic Neurons Is Mediated by the Melanocortin Pathway

BACKGROUND: The nuclear receptor chicken ovalbumin upstream promoter transcription factor II (COUP-TFII) is an important coordinator of glucose homeostasis. We report, for the first time, a unique differential regulation of its expression by the nutritional status in the mouse hypothalamus compared to peripheral tissues. METHODOLOGY/PRINCIPAL FINDINGS: Using hyperinsulinemic-euglycemic clamps and insulinopenic mice, we show that insulin upregulates its expression in the hypothalamus. Immunofluorescence studies demonstrate that COUP-TFII gene expression is restricted to a subpopulation of ventromedial hypothalamic neurons expressing the melanocortin receptor. In GT1-7 hypothalamic cells, the MC4-R agonist MTII leads to a dose dependant increase of COUP-TFII gene expression secondarily to a local increase in cAMP concentrations. Transfection experiments, using a COUP-TFII promoter containing a functional cAMP responsive element, suggest a direct transcriptional activation by cAMP. Finally, we show that the fed state or intracerebroventricular injections of MTII in mice induce an increased hypothalamic COUP-TFII expression associated with a decreased hepatic and pancreatic COUP-TFII expression. CONCLUSIONS/SIGNIFICANCE: These observations strongly suggest that hypothalamic COUP-TFII gene expression could be a central integrator of insulin and melanocortin signaling pathway within the ventromedial hypothalamus. COUP-TFII could play a crucial role in brain integration of circulating signal of hunger and satiety involved in energy balance regulation

Phagosomal Rupture by Mycobacterium tuberculosis Results in Toxicity and Host Cell Death

Survival within macrophages is a central feature of Mycobacterium tuberculosis pathogenesis. Despite significant advances in identifying new immunological parameters associated with mycobacterial disease, some basic questions on the intracellular fate of the causative agent of human tuberculosis in antigen-presenting cells are still under debate. To get novel insights into this matter, we used a single-cell fluorescence resonance energy transfer (FRET)-based method to investigate the potential cytosolic access of M. tuberculosis and the resulting cellular consequences in an unbiased, quantitative way. Analysis of thousands of THP-1 macrophages infected with selected wild-type or mutant strains of the M. tuberculosis complex unambiguously showed that M. tuberculosis induced a change in the FRET signal after 3 to 4 days of infection, indicating phagolysosomal rupture and cytosolic access. These effects were not seen for the strains M. tuberculosisΔRD1 or BCG, both lacking the ESX-1 secreted protein ESAT-6, which reportedly shows membrane-lysing properties. Complementation of these strains with the ESX-1 secretion system of M. tuberculosis restored the ability to cause phagolysosomal rupture. In addition, control experiments with the fish pathogen Mycobacterium marinum showed phagolysosomal translocation only for ESX-1 intact strains, further validating our experimental approach. Most importantly, for M. tuberculosis as well as for M. marinum we observed that phagolysosomal rupture was followed by necrotic cell death of the infected macrophages, whereas ESX-1 deletion- or truncation-mutants that remained enclosed within phagolysosomal compartments did not induce such cytotoxicity. Hence, we provide a novel mechanism how ESX-1 competent, virulent M. tuberculosis and M. marinum strains induce host cell death and thereby escape innate host defenses and favor their spread to new cells. In this respect, our results also open new research directions in relation with the extracellular localization of M. tuberculosis inside necrotic lesions that can now be tackled from a completely new perspective

Updates on radiotherapy-immunotherapy combinations: Proceedings of 6(th) annual ImmunoRad conference

Focal radiation therapy (RT) has attracted considerable attention as a combinatorial partner for immunotherapy (IT), largely reflecting a well-defined, predictable safety profile and at least some potential for immunostimulation. However, only a few RT-IT combinations have been tested successfully in patients with cancer, highlighting the urgent need for an improved understanding of the interaction between RT and IT in both preclinical and clinical scenarios. Every year since 2016, ImmunoRad gathers experts working at the interface between RT and IT to provide a forum for education and discussion, with the ultimate goal of fostering progress in the field at both preclinical and clinical levels. Here, we summarize the key concepts and findings presented at the Sixth Annual ImmunoRad conference

Use of quantitative EELS and cathodoluminescence for study of carrier confinement and diffusion in self organized vertical quantum wells

When AxGa1-xAs layers are grown on V-grooved GaAs substrates by metal organic chemical vapour deposition (MOCVD), a Ga rich vertical quantum well (VQW) appears in the V-groove centre. The width and Ga enrichment of this structure depend on the nominal Al concentration and growth temperature. From EELS linescans and spectrum images, concentration profiles and maps of VQWs are obtained, and a subsequent bandstructure calculation shows up to three confined sublevels in the VQW. Carrier confinement in segments of modulated VQWs is demonstrated. In interconnected VQW-quantum wire structures, carrier diffusion channels were assessed by cathodoluminescence. Carrier capture into the VQW and transfer into the QWR was observed

Tracking the dynamic interplay between bacterial and host factors during pathogen-induced vacuole rupture in real time.

Escape into the host cell cytosol following invasion of mammalian cells is a common strategy used by invasive pathogens. This requires membrane rupture of the vesicular or vacuolar compartment formed around the bacteria after uptake into the host cell. The mechanism of pathogen-induced disassembly of the vacuolar membrane is poorly understood. We established a novel, robust and sensitive fluorescence microscopy method that tracks the precise time point of vacuole rupture upon uptake of Gram-negative bacteria. This revealed that the enteroinvasive pathogen Shigella flexneri escapes rapidly, in less than 10 min, from the vacuole. Our method demonstrated the recruitment of host factors, such as RhoA, to the bacterial entry site and their continued presence at the point of vacuole rupture. We found a novel host marker for ruptured vacuoles, galectin-3, which appears instantly in the proximity of bacteria after escape into the cytosol. Furthermore, we show that the Salmonella effector proteins, SifA and PipB2, stabilize the vacuole membrane inhibiting bacterial escape from the vacuole. Our novel approach to track vacuole rupture is ideally suited for high-content and high-throughput approaches to identify the molecular and cellular mechanisms of membrane rupture during invasion by pathogens such as viruses, bacteria and parasites

Structural and electrooptical characteristics of quantum dots emitting at 1.3 μm on gallium arsenide

We present a comprehensive study of the structural and emission properties of self-assembled InAs quantum dots emitting at 1.3 μm. The dots are grown by molecular beam epitaxy on gallium arsenide substrates. Room-temperature emission at 1.3 μm is obtained by embedding the dots in an InGaAs layer. Depending on the growth structure, dot densities of 1-6×1010 cm-2 are obtained. High dot densities are associated with large inhomogeneous broadenings, while narrow photoluminescence (PL) linewidths are obtained in low-density samples. From time-resolved PL experiments, a long carrier lifetime of ≈1.8 ns is measured at room temperature, which confirms the excellent structural quality. A fast PL rise (τrise=10±2 ps) is observed at all temperatures, indicating the potential for high-speed modulation. High-efficiency light-emitting diodes (LEDs) based on these dots are demonstrated, with external quantum efficiency of 1% at room temperature. This corresponds to an estimated 13% radiative efficiency. Electroluminescence spectra under high injection allow us to determine the transition energies of excited states in the dots and bidimensional states in the adjacent InGaAs quantum well