Absence of MHC class II on cDCs results in microbial-dependent intestinal inflammation.

Conventional dendritic cells (cDCs) play an essential role in host immunity by initiating adaptive T cell responses and by serving as innate immune sensors. Although both innate and adaptive functions of cDCs are well documented, their relative importance in maintaining immune homeostasis is poorly understood. To examine the significance of cDC-initiated adaptive immunity in maintaining homeostasis, independent of their innate activities, we generated a cDC-specific Cre mouse and crossed it to a floxed MHC class II (MHCII) mouse. Absence of MHCII on cDCs resulted in chronic intestinal inflammation that was alleviated by antibiotic treatment and entirely averted under germ-free conditions. Uncoupling innate and adaptive functions of cDCs revealed that innate immune functions of cDCs are insufficient to maintain homeostasis and antigen presentation by cDCs is essential for a mutualistic relationship between the host and intestinal bacteria

25th annual computational neuroscience meeting: CNS-2016

The same neuron may play different functional roles in the neural circuits to which it belongs. For example, neurons in the Tritonia pedal ganglia may participate in variable phases of the swim motor rhythms [1]. While such neuronal functional variability is likely to play a major role the delivery of the functionality of neural systems, it is difficult to study it in most nervous systems. We work on the pyloric rhythm network of the crustacean stomatogastric ganglion (STG) [2]. Typically network models of the STG treat neurons of the same functional type as a single model neuron (e.g. PD neurons), assuming the same conductance parameters for these neurons and implying their synchronous firing [3, 4]. However, simultaneous recording of PD neurons shows differences between the timings of spikes of these neurons. This may indicate functional variability of these neurons. Here we modelled separately the two PD neurons of the STG in a multi-neuron model of the pyloric network. Our neuron models comply with known correlations between conductance parameters of ionic currents. Our results reproduce the experimental finding of increasing spike time distance between spikes originating from the two model PD neurons during their synchronised burst phase. The PD neuron with the larger calcium conductance generates its spikes before the other PD neuron. Larger potassium conductance values in the follower neuron imply longer delays between spikes, see Fig. 17.Neuromodulators change the conductance parameters of neurons and maintain the ratios of these parameters [5]. Our results show that such changes may shift the individual contribution of two PD neurons to the PD-phase of the pyloric rhythm altering their functionality within this rhythm. Our work paves the way towards an accessible experimental and computational framework for the analysis of the mechanisms and impact of functional variability of neurons within the neural circuits to which they belong

Nonstationarity of the link between the Tropics and the summer East Atlantic pattern

A 700-year pre-industrial control run with the MPI-ESM-LR model is used to investigate the link between the summer East Atlantic (SEA) pattern and the Pacific-Caribbean rainfall dipole (PCD), a link that has previously been shown using ERA-Interim reanalysis data. In the model, it is found that the link between the SEA and PCD is present in some multidecadal epochs but not in others. A simple statistical model reproduces this behaviour. In the statistical model, the SEA is represented by a white noise process plus a weak influence from the PCD based on the full 700 years of the model run. The statistical model is relevant to other extratropical modes of variability, for example, the winter North Atlantic Oscillation (NAO), that are weakly influenced by the Tropics. It follows that the link between the Tropics and the winter NAO is likely to undergo modulation on multidecadal time scales, as found in some previous studies. The results suggest that any predictability of the SEA, and by implication the NAO, based on tropical rainfall may not be robust and may, in fact, be modulated on multidecadal time scales, with implications for seasonal and decadal prediction systems

Inducible targeting of cDCs and their subsets in vivo

Conventional dendritic cells (cDCs) are essential immune cells linking the innate and adaptive immune system. cDC depletion in mice is an important method to study the function of these cells in vivo. Here we report an inducible in vivo system for cDC depletion in which excision of a loxP flanked Stop signal enables expression of the human diphtheria toxin receptor (DTR) under the control of Zbtb46 (zDC(lSlDTR)). cDCs can be specifically depleted by combining zDC(lSlDTR) mice with a Csf1r(Cre) driver line. In addition, we show that zDC(Cre) mice can be used to produce cDC specific conditional knockout mice (Irf8, Irf4, Notch2) which lack specific subsets of cDCs

SARS-CoV-2 seroconversions and chains of infection in healthcare professionals in a German maximum care provider (The CoSHeP study)

Introduction!#!The CoSHeP study provides novel data on SARS-CoV-2 seroconversion rates in healthcare professionals (HP) at risk at the University Hospital Bonn, a maximum healthcare provider in a region of 900.000 inhabitants.!##!Methods!#!Single-center, longitudinal observational study investigating rate of SARS-CoV-2 IgG seroconversion in HP at 2 time-points. SARS-CoV-2 IgG was measured with Roche Elecsys Anti-SARS-CoV-2 assay.!##!Results!#!Overall, 150 HP were included. Median age was 35 (range: 19-68). Main operational areas were intensive care unit (53%, n = 80), emergency room (31%, n = 46), and infectious disease department (16%, n = 24). SARS-CoV-2-IgG was detected in 5 participants (3%) at inclusion in May/June 2020, and in another 11 participants at follow-up (December 2020/ January 2021). Of the 16 seropositive participants, 14 had already known their SARS-CoV-2 infection because they had performed a PCR-test previously triggered by symptoms. Trailing chains of infection by self-assessment, 31% (n = 5) of infections were acquired through private contacts, 25% (n = 4) most likely through semi-private contacts during work. 13% (n = 2) were assumed to result through contact with contagious patients, further trailing was unsuccessful in 31% (n = 5). All five participants positive for SARS-CoV-2 IgG at inclusion remained positive with a median of 7 months after infection.!##!Discussion!#!Frontline HP caring for hospitalized patients with COVID-19 are at higher risk of SARS-CoV-2 infections. Noteworthy, based upon identified chains of infection most of the infections were acquired in private environment and semi-private contacts during work. The low rate of infection through infectious patients reveals that professional hygiene standards are effective in preventing SARS-CoV-2 infections in HP. Persisting SARS-CoV-2-IgG might indicate longer lasting immunity supporting prioritization of negative HP for vaccination

Mitochondrial Dysfunction Contributes to Impaired Cytokine Production of CD56(bright) Natural Killer Cells From Human Immunodeficiency Virus-Infected Individuals Under Effective Antiretroviral Therapy

Human immunodeficiency virus (HIV) infection is associated with impaired natural killer (NK) cell activity, which is only incompletely restored under antiretroviral therapy. Analyzing the bioenergetics profiles of oxygen consumption, we observed that several parameters were significantly reduced in HIV+ NK cells, indicating a mitochondrial defect. Accordingly, we found HIV+ CD56(bright) NK cells to display a decreased mitochondrial membrane potential and mitochondrial mass. Both parameters were positively correlated with interferon gamma (IFN-gamma) production of NK cells. Finally, we demonstrated that stimulation of HIV+ NK cells with MitoTEMPO, a mitochondria-targeting antioxidant, significantly improved IFN-gamma production. We identified mitochondrial dysfunction as a mechanism that contributes to impaired NK cell function

HIV-Associated Microbial Translocation May Affect Cytokine Production of CD56(bright) NK Cells via Stimulation of Monocytes

The mechanisms involved in HIV-associated natural killer (NK) cell impairment are still incompletely understood. We observed HIV infection to be associated with increased plasma levels of IFABP, a marker for gut epithelial barrier dysfunction, and LBP, a marker for microbial translocation. Both IFABP and LBP plasma concentrations were inversely correlated with NK cell interferon-gamma production, suggesting microbial translocation to modulate NK cell functions. Accordingly, we found lipopolysaccharide to have an indirect inhibitory effect on NK cells via triggering monocytes' transforming growth factor-beta production. Taken together, our data suggest increased microbial translocation to be involved in HIV-associated NK cell dysfunction

Early IFN-α signatures and persistent dysfunction are distinguishing features of NK cells in severe COVID-19.

Longitudinal analyses of the innate immune system, including the earliest time points, are essential to understand the immunopathogenesis and clinical course of coronavirus disease (COVID-19). Here, we performed a detailed characterization of natural killer (NK) cells in 205 patients (403 samples; days 2 to 41 after symptom onset) from four independent cohorts using single-cell transcriptomics and proteomics together with functional studies. We found elevated interferon (IFN)-α plasma levels in early severe COVD-19 alongside increased NK cell expression of IFN-stimulated genes (ISGs) and genes involved in IFN-α signaling, while upregulation of tumor necrosis factor (TNF)-induced genes was observed in moderate diseases. NK cells exert anti-SARS-CoV-2 (severe acute respiratory syndrome coronavirus 2) activity but are functionally impaired in severe COVID-19. Further, NK cell dysfunction may be relevant for the development of fibrotic lung disease in severe COVID-19, as NK cells exhibited impaired anti-fibrotic activity. Our study indicates preferential IFN-α and TNF responses in severe and moderate COVID-19, respectively, and associates a prolonged IFN-α-induced NK cell response with poorer disease outcome

Disease severity-specific neutrophil signatures in blood transcriptomes stratify COVID-19 patients

Background!#!The SARS-CoV-2 pandemic is currently leading to increasing numbers of COVID-19 patients all over the world. Clinical presentations range from asymptomatic, mild respiratory tract infection, to severe cases with acute respiratory distress syndrome, respiratory failure, and death. Reports on a dysregulated immune system in the severe cases call for a better characterization and understanding of the changes in the immune system.!##!Methods!#!In order to dissect COVID-19-driven immune host responses, we performed RNA-seq of whole blood cell transcriptomes and granulocyte preparations from mild and severe COVID-19 patients and analyzed the data using a combination of conventional and data-driven co-expression analysis. Additionally, publicly available data was used to show the distinction from COVID-19 to other diseases. Reverse drug target prediction was used to identify known or novel drug candidates based on finding from data-driven findings.!##!Results!#!Here, we profiled whole blood transcriptomes of 39 COVID-19 patients and 10 control donors enabling a data-driven stratification based on molecular phenotype. Neutrophil activation-associated signatures were prominently enriched in severe patient groups, which was corroborated in whole blood transcriptomes from an independent second cohort of 30 as well as in granulocyte samples from a third cohort of 16 COVID-19 patients (44 samples). Comparison of COVID-19 blood transcriptomes with those of a collection of over 3100 samples derived from 12 different viral infections, inflammatory diseases, and independent control samples revealed highly specific transcriptome signatures for COVID-19. Further, stratified transcriptomes predicted patient subgroup-specific drug candidates targeting the dysregulated systemic immune response of the host.!##!Conclusions!#!Our study provides novel insights in the distinct molecular subgroups or phenotypes that are not simply explained by clinical parameters. We show that whole blood transcriptomes are extremely informative for COVID-19 since they capture granulocytes which are major drivers of disease severity