Biology subjects

Koch, M.

Publications and source records attributed to Koch, M..

At least 55 records · Page 3Linked to original sources

bioRxiv2021

Intranasal administration of a monoclonal neutralizing antibody protects mice against SARS-CoV-2 infection

Despite recent availability of vaccines against severe acute respiratory syndrome coronavirus type 2 (SARS-CoV-2), there is an urgent need for specific anti-SARS-CoV-2 drugs. Monoclonal neutralizing antibodies are an important drug class in the global fight against the SARS-CoV-2 pandemic due to their ability to convey immediate protection and their potential to be used as both, prophylactic and therapeutic drugs. Clinically used neutralizing antibodies against respiratory viruses are currently injected intravenously, which can lead to suboptimal pulmonary bioavailability and thus to a lower effectiveness. Here we describe DZIF-10c, a fully human monoclonal neutralizing antibody that binds the receptor-binding domain of SARS-CoV-2 spike protein. DZIF-10c displays an exceptionally high neutralizing potency against SARS-CoV-2 and retains activity against the variants of concern B.1.1.7 and B.1.351. Importantly, not only systemic but also intranasal application of DZIF-10c abolished presence of infectious particles in the lungs of SARS-CoV-2 infected mice and mitigated lung pathology. Along with a favorable pharmacokinetic profile, these results highlight DZIF-10c as a novel human SARS-CoV-2 neutralizing antibody with high in vitro and in vivo antiviral potency. The successful intranasal application of DZIF-10c paves the way for clinical trials investigating topical delivery of anti-SARS-CoV-2 antibodies. Significance StatementMonoclonal neutralizing antibodies are important in the global fight against the SARS-CoV-2 pandemic due to their ability to convey immediate protection. However, their intravenous application might lead to suboptimal bioavailability in the lung. We here precisely characterize a new monoclonal neutralizing antibody (DZIF-10c) that binds to the receptor binding domain of the spike protein of SARS-CoV-2. DZIF-10c neutralizes SARS-CoV-2 with exceptionally high potency and maintains activity against circulating variants of concern. The antibody has a favorable pharmacokinetic profile and protects mice from SARS-CoV-2 infection. Importantly, we show that intranasal administration of DZIF-10c generates protective efficacy. These results not only identify DZIF-10c as a novel highly potent neutralizing antibody, but further pave the way for a topical application of anti-SARS-CoV-2 antibodies.

microbiology↗

bioRxiv2021

Evaluation of mRNA-1273 against SARS-CoV-2 B.1.351 Infection in Nonhuman Primates

BackgroundVaccine efficacy against the B.1.351 variant following mRNA-1273 vaccination in humans has not been determined. Nonhuman primates (NHP) are a useful model for demonstrating whether mRNA-1273 mediates protection against B.1.351. MethodsNonhuman primates received 30 or 100 {micro}g of mRNA-1273 as a prime-boost vaccine at 0 and 4 weeks, a single immunization of 30 {micro}g at week 0, or no vaccine. Antibody and T cell responses were assessed in blood, bronchioalveolar lavages (BAL), and nasal washes. Viral replication in BAL and nasal swabs were determined by qRT-PCR for sgRNA, and histopathology and viral antigen quantification were performed on lung tissue post-challenge. ResultsEight weeks post-boost, 100 {micro}g x2 of mRNA-1273 induced reciprocal ID50 neutralizing geometric mean titers against live SARS-CoV-2 D614G and B.1.351 of 3300 and 240, respectively, and 430 and 84 for the 30 {micro}g x2 group. There were no detectable neutralizing antibodies against B.1351 after the single immunization of 30 {micro}g. On day 2 following B.1.351 challenge, sgRNA in BAL was undetectable in 6 of 8 NHP that received 100 {micro}g x2 of mRNA-1273, and there was a [~]2-log reduction in sgRNA in NHP that received two doses of 30 {micro}g compared to controls. In nasal swabs, there was a 1-log10 reduction observed in the 100 {micro}g x2 group. There was limited inflammation or viral antigen in lungs of vaccinated NHP post-challenge. ConclusionsImmunization with two doses of mRNA-1273 achieves effective immunity that rapidly controls lower and upper airway viral replication against the B.1.351 variant in NHP.

immunology↗

bioRxiv2021

Vesicle-bound regulatory RNAs are associated with tissue aging

Previous work on murine models and human demonstrated global as well as tissue-specific molecular aging trajectories in solid tissues and body fluids1-8. Extracellular vesicles like exosomes play a crucial role in communication and information exchange in between such systemic factors and solid tissues9,10. We sequenced freely circulating and vesicle-bound small regulatory RNAs in mice at five time points across the average life span from 2 to 18 months. Intriguingly, each small RNA class exhibits unique aging patterns, which showed differential signatures between vesicle-bound and freely circulating molecules. In particular, tRNA fragments showed overall highest correlation with aging which also matched well between sample types, facilitating age prediction with non-negative matrix factorization (86% accuracy). Interestingly, rRNAs exhibited inverse correlation trajectories between vesicles and plasma while vesicle-bound microRNAs (miRNAs) were exceptionally strong associated with aging. Affected miRNAs regulate the inflammatory response and transcriptional processes, and adipose tissues show considerable effects in associated gene regulatory modules. Finally, nanoparticle tracking and electron microscopy suggest a shift from overall many small to fewer but larger vesicles in aged plasma, potentially contributing to systemic aging trajectories and affecting the molecular aging of organs.

molecular biology↗

bioRxiv2021

Immune Correlates of Protection by mRNA-1273 Immunization against SARS-CoV-2 Infection in Nonhuman Primates

Immune correlates of protection can be used as surrogate endpoints for vaccine efficacy. The nonhuman primate (NHP) model of SARS-CoV-2 infection replicates key features of human infection and may be used to define immune correlates of protection following vaccination. Here, NHP received either no vaccine or doses ranging from 0.3 - 100 g of mRNA-1273, a mRNA vaccine encoding the prefusion-stabilized SARS-CoV-2 spike (S-2P) protein encapsulated in a lipid nanoparticle. mRNA-1273 vaccination elicited robust circulating and mucosal antibody responses in a dose-dependent manner. Viral replication was significantly reduced in bronchoalveolar lavages and nasal swabs following SARS-CoV-2 challenge in vaccinated animals and was most strongly correlated with levels of anti-S antibody binding and neutralizing activity. Consistent with antibodies being a correlate of protection, passive transfer of vaccine-induced IgG to naive hamsters was sufficient to mediate protection. Taken together, these data show that mRNA-1273 vaccine-induced humoral immune responses are a mechanistic correlate of protection against SARS-CoV-2 infection in NHP. One-Sentence SummarymRNA-1273 vaccine-induced antibody responses are a mechanistic correlate of protection against SARS-CoV-2 infection in NHP.

immunology↗

bioRxiv2021

Variant SARS-CoV-2 mRNA vaccines confer broad neutralization as primary or booster series in mice

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is the causative agent of a global pandemic. Safe and effective COVID-19 vaccines are now available, including mRNA-1273, which has shown 94% efficacy in prevention of symptomatic COVID-19 disease. However, the emergence of SARS-CoV-2 variants has led to concerns of viral escape from vaccine-induced immunity. Several variants have shown decreased susceptibility to neutralization by vaccine-induced immunity, most notably B.1.351 (Beta), although the overall impact on vaccine efficacy remains to be determined. Here, we present the initial evaluation in mice of 2 updated mRNA vaccines designed to target SARS-CoV-2 variants: (1) monovalent mRNA-1273.351 encodes for the spike protein found in B.1.351 and (2) mRNA-1273.211 comprising a 1:1 mix of mRNA-1273 and mRNA-1273.351. Both vaccines were evaluated as a 2-dose primary series in mice; mRNA-1273.351 was also evaluated as a booster dose in animals previously vaccinated with mRNA-1273. The results demonstrated that a primary vaccination series of mRNA-1273.351 was effective at increasing neutralizing antibody titers against B.1.351, while mRNA-1273.211 was effective at providing broad cross-variant neutralization. A third (booster) dose of mRNA-1273.351 significantly increased both wild-type and B.1.351-specific neutralization titers. Both mRNA-1273.351 and mRNA-1273.211 are being evaluated in pre-clinical challenge and clinical studies.

microbiology↗

bioRxiv2021

Identification of candidate genes for self-compatibility in perennial ryegrass (Lolium perenne L.)

Self-incompatibility (SI) is a genetic mechanism preventing self-pollination in approximately 40% of plant species. Two multiallelic loci, called S and Z, control the gametophytic SI system of the grass family (Poaceae), which contains all major forage grasses. Loci independent from S and Z have been reported to disrupt SI and lead to self-compatibility (SC). A locus causing SC in perennial ryegrass (Lolium perenne L.) was previously mapped on linkage group (LG) 5 in a F2 population segregating for SC. Using a subset of the same population (n=68), we first performed low-resolution quantitative trait locus (QTL) mapping to exclude the presence of additional, previously undetected contributors to SC. The previously reported QTL on LG 5 explained 38.4% of the phenotypic variation, and no significant contribution from other genomic regions was found. This was verified by the presence of significantly distorted markers in the region overlapping with the QTL. Second, we fine mapped the QTL to 0.26 cM using additional 2,056 plants and 23 novel sequence-based markers. Using an Italian ryegrass (Lolium multiflorum Lam.) genome assembly as reference, the markers flanking SC were estimated to span a ~3 Mb region encoding for 57 predicted genes. Among these, seven genes were proposed as relevant candidate genes based on their annotation and function described in previous studies. Our work is a step forward to identify SC genes in forage grasses and provides diagnostic markers for marker-assisted introgression of SC into elite germplasm. Key messageA previously reported QTL conferring self-compatibility to perennial ryegrass was fine mapped to a 0.26 cM locus, corresponding to an estimated ~ 3 Mb physical region containing 57 predicted protein-encoding genes.

plant biology↗

bioRxiv2021

mRNA-1273 vaccine induces neutralizing antibodies against spike mutants from global SARS-CoV-2 variants

Severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) is the causative infection of a global pandemic that has led to more than 2 million deaths worldwide. The Moderna mRNA-1273 vaccine has demonstrated ~94% efficacy in a Phase 3 study and has been approved under Emergency Use Authorization. The emergence of SARS-CoV-2 variants with mutations in the spike protein, most recently circulating isolates from the United Kingdom (B.1.1.7) and Republic of South Africa (B.1.351), has led to lower neutralization from convalescent serum by pseudovirus neutralization (PsVN) assays and resistance to certain monoclonal antibodies. Here, using two orthogonal VSV and lentivirus PsVN assays expressing spike variants of 20E (EU1), 20A.EU2, D614G-N439, mink cluster 5, B.1.1.7, and B.1.351 variants, we assessed the neutralizing capacity of sera from human subjects or non-human primates (NHPs) that received mRNA-1273. No significant impact on neutralization against the B.1.1.7 variant was detected in either case, however reduced neutralization was measured against the mutations present in B.1.351. Geometric mean titer (GMT) of human sera from clinical trial participants in VSV PsVN assay using D614G spike was 1/1852. VSV pseudoviruses with spike containing K417N-E484K-N501Y-D614G and full B.1.351 mutations resulted in 2.7 and 6.4-fold GMT reduction, respectively, when compared to the D614G VSV pseudovirus. Importantly, the VSV PsVN GMT of these human sera to the full B.1.351 spike variant was still 1/290, with all evaluated sera able to fully neutralize. Similarly, sera from NHPs immunized with 30 or 100g of mRNA-1273 had VSV PsVN GMTs of ~ 1/323 or 1/404, respectively, against the full B.1.351 spike variant with a ~ 5 to 10-fold reduction compared to D614G. Individual mutations that are characteristic of the B.1.1.7 and B.1.351 variants had a similar impact on neutralization when tested in VSV or in lentivirus PsVN assays. Despite the observed decreases, the GMT of VSV PsVN titers in human vaccinee sera against the B.1.351 variant remained at ~1/300. Taken together these data demonstrate reduced but still significant neutralization against the full B.1.351 variant following mRNA-1273 vaccination.

immunology↗

bioRxiv2021

A novel universal algorithm for filament network tracing and cytoskeleton analysis

The rapid development of advanced microscopy techniques over recent decades has significantly increased the quality of imaging and our understanding of subcellular structures, such as the organization of the filaments of the cytoskeleton using fluorescence and electron microscopy. However, these recent improvements in imaging techniques have not been matched by similar development of techniques for computational analysis of the images of filament networks that can now be obtained. Hence, for a wide range of applications, reliable computational analysis of such two-dimensional (2D) methods remains challenging. Here, we present a new algorithm for tracing of filament networks. This software can extract many important parameters from grayscale images of filament networks, including the Mesh Hole Size, and Filament Length and Connectivity (also known as Coordination Number. In addition, the method allows sub-networks to be distinguished in 2D images using intensity thresholding. We show that the algorithm can be used to analyze images of cytoskeleton networks obtained using different advanced microscopy methods. We have thus developed a new improved method for computational analysis of 2D images of filamentous networks that has wide applications for existing imaging techniques. The algorithm is available as open-source software.

biophysics↗

bioRxiv2020

LL-37 fights SARS-CoV-2: The Vitamin D-Inducible Peptide LL-37 Inhibits Binding of SARS-CoV-2 Spike Protein to its Cellular Receptor Angiotensin Converting Enzyme 2 In Vitro

ObjectiveSevere acute respiratory syndrome coronavirus-2 (SARS-CoV-2) is the pathogen accountable for the coronavirus disease 2019 (COVID-19) pandemic. Viral entry via binding of the receptor binding domain (RBD) located within the S1 subunit of the SARS-CoV-2 Spike (S) protein to its target receptor angiotensin converting enzyme (ACE) 2 is a key step in cell infection. The efficient transition of the virus is linked to a unique protein called open reading frame (ORF) 8. As SARS-CoV-2 infections can develop into life-threatening lower respiratory syndromes, effective therapy options are urgently needed. Several publications propose vitamin D treatment, although its mode of action against COVID-19 is not fully elucidated. It is speculated that vitamin Ds beneficial effects are mediated by up-regulating LL-37, a well-known antimicrobial peptide with antiviral effects. MethodsRecombinantly expressed SARS-CoV-2 S protein, the extended S1 subunit (S1e), the S2 subunit (S2), the receptor binding domain (RBD), and ORF8 were used for surface plasmon resonance (SPR) studies to investigate LL-37s ability to bind to SARS-CoV-2 proteins and to localize its binding site within the S protein. Binding competition studies were conducted to confirm an inhibitory action of LL-37 on the attachment of SARS-CoV-2 S protein to its entry receptor ACE2. ResultsWe could show that LL-37 binds to SARS-CoV-2 S protein (LL-37/SStrep KD = 410 nM, LL-37/SHis KD = 410 nM) with the same affinity, as SARS-CoV-2 binds to hACE2 (hACE2/SStrep KD = 370 nM, hACE2/SHis KD = 370 nM). The binding is not restricted to the RBD of the S protein, but rather distributed along the entire length of the protein. Interaction between LL-37 and ORF8 was detected with a KD of 290 nM. Further, inhibition of the binding of SStrep (IC50 = 740 nM), S1e (IC50 = 170 nM), and RBD (IC50 = 130 nM) to hACE2 by LL-37 was demonstrated. ConclusionsWe have revealed a biochemical link between vitamin D, LL-37, and COVID-19 severity. SPR analysis demonstrated that LL-37 binds to SARS-CoV-2 S protein and inhibits binding to its receptor hACE2, and most likely viral entry into the cell. This study supports the prophylactic use of vitamin D to induce LL-37 that protects from SARS-CoV-2 infection, and the therapeutic administration of vitamin D for the treatment of COVID-19 patients. Further, our results provide evidence that the direct use of LL-37 by inhalation and systemic application may reduce the severity of COVID-19.

immunology↗

bioRxiv2020

Degradation of mixed-linkage (1,3;1,4)-β-D-glucan in maize is mediated by the CAL1 licheninase

The presence of mixed-linkage (1,3;1,4)-{beta}-D-glucan (MLG) in plant cell walls is a key feature of grass species such as cereals - the main source of calorie intake for humans and cattle. Accumulation of this polysaccharide involves the coordinated regulation of biosynthetic and metabolic machineries. While several components of the MLG biosynthesis machinery have been identified in diverse plant species, degradation of MLG is poorly understood. A large-scale forward genetic maize screen for mutants with altered cell wall polysaccharide structural properties resulted in the identification of candy-leaf1 (cal1). Cell walls of CAL1-deficient plants contain higher amounts of MLG in several tissues, including adult leaves and senesced organs, where only trace amounts of MLG are usually detected. In addition, cal1 plants exhibit increased saccharification yields upon enzymatic digestion. Stacking cal1 with lignin-deficient mutations results in synergistic saccharification increases. Identification of the causative mutation revealed that CAL1 encodes a GH17 licheninase. Maize plants overexpressing CAL1 exhibit a 90% reduction in MLG content, indicating that CAL1 is not only required, but its expression sufficient to degrade MLG. CAL1 specifically hydrolyzes (1,3;1,4)-{beta}-D-Glucans in vitro, and the single CAL1E262K amino acid substitution is able to block all detectable activity. Time profiling experiments indicate that wall MLG content is modulated during day/night cycles inversely correlating with CAL1 transcript accumulation. This cycling is absent in the cal1 mutant, suggesting that the mechanism involved requires MLG degradation that may in turn regulate CAL1 gene expression. One sentence summary Mixed-linkage glucan is degraded by the CAL1 licheninase in maize

plant biology↗

bioRxiv2020

Maximizing PHB content in Synechocystis sp. PCC 6803: development of a new photosynthetic overproduction strain.

PHB (poly-hydroxy-butyrate) represents a promising bioplastic variety with good biodegradation properties. Furthermore, PHB can be produced completely carbon-neutral when synthesized in the natural producer cyanobacterium Synechocystis sp. PCC 6803. This model strain has a long history of various attempts to further boost its low amounts of produced intracellular PHB of ~15 % per cell-dry-weight (CDW). We have created a new strain that lacks the regulatory protein PirC (gene product of sll0944), which causes a rapid conversion of the intracellular glycogen pools to PHB under nutrient limiting conditions. To further improve the intracellular PHB content, two genes from the PHB metabolism, phaA and phaB from the known production strain Cupriavidus necator, were introduced under the regime of the strong promotor PpsbA2. The created strain, termed PPT1 ({Delta}sll0944-REphaAB), produced high amounts of PHB under continuous light as well under day-night rhythm. When grown in nitrogen and phosphor depleted medium, the cells produced up to 63 % / CDW. Upon the addition of acetate, the content was further increased to 81 % / CDW. The produced polymer consists of pure PHB, which is highly isotactic. The achieved amounts were the highest ever reported in any known cyanobacterium and demonstrate the potential of cyanobacteria for a sustainable, industrial production of PHB.

microbiology↗

bioRxiv2020

The Novel PII-Interacting Regulator PirC (Sll0944) Identifies 3-Phosphoglycerate Mutase (PGAM) as Central Control Point of Carbon Storage Metabolism in Cyanobacteria

Nitrogen limitation imposes a major transition in the life-style of non-diazotrophic cyanobacteria, which is regulated via a complex interplay of regulatory factors, involving, the nitrogen-specific transcription factor NtcA and the pervasive signal processor PII. Immediately upon nitrogen-limitation, newly fixed carbon is re-directed towards glycogen synthesis. How the metabolic switch for distributing fixed carbon to either glycogen or cellular building blocks is operated was poorly understood. Here we identify from Synechocystis sp. PCC 6803 a novel PII interactor, PirC, (Sll0944) that controls 3-phosphoglycerate mutase (PGAM), the enzyme that deviates newly fixed CO2 towards lower glycolysis. PirC acts as competitive inhibitor of PGAM and this interaction is tuned by PII/2-oxoglutarate. High oxoglutarate release PirC from PII-complex to inhibit PGAM. Accordingly, PirC deficient mutant, as compared to the wild-type, shows strongly reduced glycogen levels upon nitrogen deprivation whereas polyhydroxybutyrate granules are over-accumulated. Metabolome analysis revealed an imbalance in 3-phosphoglycerate to pyruvate levels in the PirC mutant, conforming that PirC controls the carbon flux in cyanobacteria via mutually exclusive interaction with either PII or PGAM.

microbiology↗

bioRxiv2020

Growth hormone receptor (GHR)-expressing neurons in the hypothalamic arcuate nucleus regulate glucose metabolism and energy homeostasis

Growth hormone (GH) receptor (GHR), expressed in different brain regions, is known to participate in the regulation of whole-body energy homeostasis and glucose metabolism. However, GH activation of these GHR-expressing neurons is less studied. We have generated a novel GHR-driven Cre recombinase transgenic mouse line (GHRcre) in combination with the floxed tdTomato reporter mouse line we tracked and activated GHR-expressing neurons in different regions of the brain. We focused on neurons of the hypothalamic arcuate nucleus (ARC) where GHR was shown to elicit a negative feedback loop that regulates GH production. We found that ARCGHR+ neurons are co-localized with AgRP, GHRH, and somatostatin neurons, which were activated by GH stimulation. Using designer receptors exclusively activated by designer drugs (DREADDs) to control GHRARC neuronal activity, we revealed that activation of GHRARC neurons was sufficient in regulating distinct aspects of energy balance and glucose metabolism. Overall, our study provides a novel mouse model to study in vivo regulation and physiological function of GHR-expressing neurons in various brain regions. Furthermore, we identified for the first time specific neuronal population that responds to GH and directly linked it to metabolic responses in vivo.

neuroscience↗

bioRxiv2020

Long-term live imaging of epithelial organoids and corresponding multiscale analysis reveal high heterogeneity and identifies core regulatory principles

Organoids are morphologically heterogeneous three-dimensional cell culture systems. To understand the cell organisation principles of their morphogenesis, we imaged hundreds of pancreas and liver organoids in parallel using light sheet and bright field microscopy for up to seven days. We quantified organoid behaviour at single-cell (microscale), individual-organoid (mesoscale), and entire-culture (macroscale) levels. At single-cell resolution, we monitored formation, monolayer polarisation and degeneration, and identified diverse behaviours, including lumen expansion and decline (size oscillation), migration, rotation and multi-organoid fusion. Detailed individual organoid quantifications lead to a mechanical 3D agent-based model. A derived scaling law and simulations support the hypotheses that size oscillations depend on organoid properties and cell division dynamics, which is confirmed by bright field macroscale analyses of entire cultures. Our multiscale analysis provides a systematic picture of the diversity of cell organisation in organoids by identifying and quantifying core regulatory principles of organoid morphogenesis. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=182 HEIGHT=200 SRC="FIGDIR/small/199463v2_ufig1.gif" ALT="Figure 1"> View larger version (37K): org.highwire.dtl.DTLVardef@1df3118org.highwire.dtl.DTLVardef@104dc7org.highwire.dtl.DTLVardef@62512forg.highwire.dtl.DTLVardef@bff752_HPS_FORMAT_FIGEXP M_FIG C_FIG Created with BioRender.com.

cell biology↗

bioRxiv2020

Loss of TP53 mediates suppression of Macrophage Effector Function via Extracellular Vesicles and PDL1 towards Resistance against Chemoimmunotherapy in B-cell malignancies

Chemoimmunotherapy (CIT) is the standard of care in B-cell malignancies. It is relying on synergistic effects of alkylating chemotherapy and monoclonal antibodies via secretory crosstalk with effector macrophages. Here, we observed that loss of p53 function mediates resistance to CIT by suppressing macrophage phagocytic function. Loss of p53 leads to an upregulation of PDL1 and an increased formation of extracellular vesicles (EVs). EVs directly inhibit macrophage phagocytosis by PDL1 surface expression. Suppression of phagocytic function by lymphoma cell-derived EVs could be abrogated by pre-incubation of EVs with anti-PDL1 antibodies, CRISPR-KO of PDL1 and abrogation of EV formation by RAB27A-KO in lymphoma cells. Immune checkpoint inhibition represents a viable strategy to overcome EV-mediated resistance to chemoimmunotherapy in lymphoma. SignificanceLoss of TP53 mediates cell autonomous resistance to genotoxic chemotherapy, moreover non-cell autonomous effects may cause therapy resistance mediated by the tumor microenvironment. We identify a TP53-dependent mechanism that mediates resistance to synergistic chemoimmunotherapy by increasing formation of EVs and expression of the PDL1 immune checkpoint. PDL1 on EVs is directly responsible for macrophage suppression, preventing the exertion of the essential effector function of antibody-dependent cellular phagocytosis. This novel mechanism of resistance is in turn targetable by PDL1 checkpoint inhibition. Enhanced EV-release and immune checkpoint expression in lymphoma are novel mechanisms of macrophage modulation in the lymphoma microenvironment. We provide a novel principle of resistance to chemoimmunotherapy (CIT) representing of immediate relevance to treatment of refractory B-cell lymphoma. HighlightsO_LILoss of TP53 in B-cell lymphoma induces resistance towards chemoimmunotherapy (CIT) by inhibition of macrophage effector function through PDL1 upregulation C_LIO_LILoss of TP53 increases formation of extracellular vesicles (EVs) carrying PDL1 C_LIO_LIEVs inhibit antibody-mediated cellular phagocytosis (ADCP), a key macrophage effector function in CIT C_LIO_LITargeting PDL1 on EVs with immune checkpoint inhibitors overcomes TP53-mediated resistance to CIT C_LI

cell biology↗

bioRxiv2020

Longitudinal isolation of potent near-germline SARS-CoV-2-neutralizing antibodies from COVID-19 patients

The SARS-CoV-2 pandemic has unprecedented implications for public health, social life, and world economy. Since approved drugs and vaccines are not available, new options for COVID-19 treatment and prevention are highly demanded. To identify SARS-CoV-2 neutralizing antibodies, we analysed the antibody response of 12 COVID-19 patients from 8 to 69 days post diagnosis. By screening 4,313 SARS-CoV-2-reactive B cells, we isolated 255 antibodies from different time points as early as 8 days post diagnosis. Among these, 28 potently neutralized authentic SARS-CoV-2 (IC100 as low as 0.04 g/ml), showing a broad spectrum of V genes and low levels of somatic mutations. Interestingly, potential precursors were identified in naive B cell repertoires from 48 healthy individuals that were sampled before the COVID-19 pandemic. Our results demonstrate that SARS-CoV-2 neutralizing antibodies are readily generated from a diverse pool of precursors, fostering the hope of rapid induction of a protective immune response upon vaccination.

immunology↗

bioRxiv2020

Faithful Scanning Electron Microscopic (SEM) visualization of 3D printed alginate-based scaffolds

The morphological characterization of 3D printed hydrogel-based scaffolds is essential for monitoring their size, shape, surface texture and internal structure. Among other microscopic techniques, Scanning Electron Microscopy (SEM) is capable of visualizing nearly all kinds of materials at different length scales, with exceptional precision, if investigation under vacuum is possible. However, due to the high water content of hydrogel-based scaffolds and the connected volume change after drying, special preparation techniques are necessary to stabilize the 3D architecture when imaged by SEM. Here we present a straightforward cryo-SEM technique to visualize 3D printed hydrogel-based alginate scaffolds. By use of a homemade cryo-SEM holder and plunge-freezing in liquid ethane, scaffolds are visualized from the top and cross-sectional view at different magnifications. The proposed method is compared with SEM imaging in different modes (cyro-SEM, conventional SEM, ESEM) following other commonly used sample preparation techniques, such as plunging in liquid nitrogen, air-drying, freeze-drying and plunging in liquid ethane after graded dehydration. These approaches, except ESEM, lead to shrinkage, deformation, distortion or disintegration of the scaffolds and consequently give rise to artifacts in imaging. The presented results indicate that cryo-SEM after plunging in liquid ethane allows for the most faithful and time-efficient visualization of 3D printed alginate scaffolds.

bioengineering↗

bioRxiv2020

Scanning electron microscopy preparation and analysis of the cell cortex ultrastructure

The cellular cortex is an approximately 200-nm-thick actin network that lies just beneath the cell membrane. It is responsible for the mechanical properties of cells, and as such, it is involved in many cellular processes, including cell migration and cellular interactions with the environment. To develop a clear view of this dense structure, high-resolution imaging is essential. As one such technique, electron microscopy, involves complex sample preparation procedures. The final drying of these samples has significant influence on potential artifacts, like cell shrinkage and the formation of artifactual holes in the actin cortex. In this study, we compared the three most used final sample drying procedures: critical-point drying (CPD), CPD with lens tissue (CPD-LT), and hexamethyldisilazane drying. We show that both hexamethyldisilazane and CPD-LT lead to fewer artifactual mesh holes within the actin cortex than CPD. Moreover, CPD-LT leads to significant reduction in cell height compared to hexamethyldisilazane and CPD. We conclude that the final drying procedure should be chosen according to the reduction in cell height, and so CPD-LT, or according to the spatial separation of the single layers of the actin cortex, and so hexamethyldisilazane.

biophysics↗