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The outbreak of coronavirus disease 2019 (COVID‐19), caused by the severe acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2), disproportionately affects certain populations, such as older individuals.1 In contrast, children comprise <2% of cases and generally exhibit milder symptoms.2 These disparate observations in children versus adults may be attributed to both environmental and host immune factors, including an immature and developing immune system.3 A key breakthrough in understanding the infectious mechanism of COVID‐19 was the discovery of angiotensin‐converting enzyme 2/ACE2, the receptor that SARS‐CoV‐2 uses to gain entry into human host cells.4 ACE2 expression is observed in the upper and lower respiratory tract and in extrapulmonary tissues that are prone to SARS‐CoV‐2 infection (e.g. gastrointestinal tract, cardiovascular system, skin).5 Lower maturity and function of ACE2 have been hypothesized to explain less disease prevalence in children

Mitochondria, chloroplasts and Gram-negative bacteria are encased in a double layer of membranes. The outer membrane contains proteins with a beta-barrel structure1,2. beta-Barrels are sheets of beta-strands wrapped into a cylinder, in which the first strand is hydrogen-bonded to the final strand. Conserved multi-subunit molecular machines fold and insert these proteins into the outer membrane(3-5). One subunit of the machines is itself a beta-barrel protein that has a central role in folding other beta-barrels. In Gram-negative bacteria, the beta-barrel assembly machine (BAM) consists of the beta-barrel protein BamA, and four lipoproteins(5-8). To understand how the BAM complex accelerates folding without using exogenous energy (for example, ATP)(9), we trapped folding intermediates on this machine. Here we report the structure of the BAM complex of Escherichia coli folding BamA itself. The BamA catalyst forms an asymmetric hybrid beta-barrel with the BamA substrate. The N-terminal edge of the BamA catalyst has an antiparallel hydrogen-bonded interface with the C-terminal edge of the BamA substrate, consistent with previous crosslinking studies(10-12); the other edges of the BamA catalyst and substrate are close to each other, but curl inward and do not pair. Six hydrogen bonds in a membrane environment make the interface between the two proteins very stable. This stability allows folding, but creates a high kinetic barrier to substrate release after folding has finished. Features at each end of the substrate overcome this barrier and promote release by stepwise exchange of hydrogen bonds. This mechanism of substrate-assisted product release explains how the BAM complex can stably associate with the substrate during folding and then turn over rapidly when folding is complete.

The foamy viruses (FV) or spumaviruses are an ancient subfamily of retroviruses that infect a variety of vertebrates. FVs are endemic, but apparently apathogenic, in modern non-human primates. Like other retroviruses, FV replication is inhibited by type-I interferon (IFN). In a previously described screen of IFN-stimulated genes (ISGs), we identified the macaque PHD finger domain protein-11 (PHF11) as an inhibitor of prototype foamy virus (PFV) replication. Here, we show that human and macaque PHF11 inhibit the replication of multiple spumaviruses, but are inactive against several orthoretroviruses. Analysis of other mammalian PHF11 proteins revealed that antiviral activity is host species dependent. Using multiple reporter viruses and cell lines, we determined that PHF11 specifically inhibits a step in the replication cycle that is unique to FVs, namely basal transcription from the FV internal promoter (IP). In so doing, PHF11 prevents expression of the viral transactivator Tas and subsequent activation of the viral LTR promoter. These studies reveal a previously unreported inhibitory mechanism in mammalian cells, that targets a family of ancient viruses and may promote viral latency. Author summary Foamy viruses have a unique replication strategy and long evolutionary relationship with their vertebrate hosts that has resulted in wide-spread infection of modern species without any apparent pathogenic consequence. How foamy virus infections are controlled by their hosts is unknown. Here, we demonstrate that infection of a variety of foamy viruses is inhibited by the interferon-stimulated gene product, PHF11, in a species-dependent manner. We show that PHF11 prevents replication by a previously undescribed mechanism, namely by inhibiting gene expression from an internal viral promoter, a conserved and distinct feature of the foamy viruses. Inhibition of early viral gene expression by PHF11 may promote viral latency and the apathogenicity of foamy viruses.

Background Skin biopsies promote our understanding of atopic dermatitis/AD pathomechanisms in infants/toddlers with early-onset AD, but are not feasible in pediatric populations. Tape strips are an emerging, minimally invasive alternative, but global transcriptomic profiling in early pediatric AD is lacking. We aimed to provide global lesional and nonlesional skin profiles of infants/toddlers with recent-onset, moderate-to-severe AD using tape strips. Methods Sixteen tape strips were collected for RNA-seq profiling from 19 infants/toddlers (<5 years old; lesional and nonlesional) with early-onset moderate-to-severe AD (<= 6 months) and 17 healthy controls. Results We identified 1829 differentially expressed genes/DEGs in lesional AD and 662 DEGs in nonlesional AD, vs healthy skin (fold-change >= 2, FDR <0.05), with 100% sample recovery. Both lesional and nonlesional skin showed significant dysregulations of Th2 (CCL17 and IL4R) and Th22/Th17 (IL36G, CCL20, and S100As)-related genes, largely lacking significant Th1-skewing. Significant down-regulation of terminal differentiation (FLG and FLG2), lipid synthesis/metabolism (ELOVL3 and FA2H), and tight junction (CLDN8) genes were primarily seen in lesional AD. Significant negative correlations were identified between Th2 measures and epidermal barrier gene-subsets and individual genes (FLG with IL-4R and CCL17;r < -0.4,P < .05). Significant correlations were also identified between clinical measures (body surface area/BSA, pruritus ADQ, and transepidermal water loss/TEWL) with immune and barrier mRNAs in lesional and/or nonlesional AD (FLG/FLG2 with TEWL;r < -0.4,P < .05). Conclusion RNA-seq profiling using tape strips in early-onset pediatric AD captures immune and barrier alterations in both lesional and nonlesional skin. Tape strips provide insight into disease pathomechanisms and cutaneous disease activity.

Two widely investigated areas of theory in ecology over the past half century are species-abundance distributions (SADs) and Taylor's power law of fluctuation scaling (TL). This paper connects TL with a classic SAD, MacArthur's broken-stick model. Each of these models is more than 60 years old, but apparently the connection has not been observed previously. For large numbers of species, the broken-stick model asymptotically obeys TL with exponent 2: the variance of species abundance equals the square of the mean species abundance. Equivalently, in the broken-stick model, the coefficient of variation of abundance is asymptotically 1. Because both the broken-stick model and TL have interpretations and applications beyond ecology, the connection established here has broader than purely ecological interest. This simple but previously unnoticed relationship between the broken-stick model and the power-law variance function raises the question of how other species-abundance distributions are related to power law or other variance functions.

The gut mounts secretory immunoglobulin A ( SIgA) responses to commensal bacteria through nonredundant T cell-dependent (TD) and T cell-independent (TI) pathways that promote the establishment of mutualistic host-microbiota interactions. SIgAs from the TD pathway target penetrant bacteria, and their induction requires engagement of CD40 on B cells by CD40 ligand on T follicular helper cells. In contrast, SIgAs from the TI pathway bind a larger spectrum of bacteria, but the mechanism underpinning their production remains elusive. Here, we show that the intestinal TI pathway required CD40-independent B cell-activating signals from TACI, a receptor for the innate CD40 ligand-like factors BAFF and APRIL. TACI-induced SIgA responses targeted a fraction of the gut microbiota without shaping its overall composition. Of note, TACI was dispensable for TD induction of IgA in gut-associated lymphoid organs. Thus, BAFF/APRIL signals acting on TACI orchestrate commensal bacteria-specific SIgA responses through an intestinal TI program.

Heritable APOE variants in patients with melanoma influence anti-tumor immunity and modulate metastatic progression and response to immunotherapy. Common germline variants of the APOE gene are major risk modifiers of neurodegenerative and atherosclerotic diseases(1-3), but their effect on cancer outcome is poorly defined. Here we report that, in a reversal of their effect on Alzheimer's disease, the APOE4 and APOE2 variants confer favorable and poor outcomes in melanoma, respectively. Mice expressing the human APOE4 allele exhibited reduced melanoma progression and metastasis relative to APOE2 mice. APOE4 mice exhibited enhanced anti-tumor immune activation relative to APOE2 mice, and T cell depletion experiments showed that the effect of APOE genotype on melanoma progression was mediated by altered anti-tumor immunity. Consistently, patients with melanoma carrying the APOE4 variant experienced improved survival in comparison to carriers of APOE2. Notably, APOE4 mice also showed improved outcomes under PD1 immune checkpoint blockade relative to APOE2 mice, and patients carrying APOE4 experienced improved anti-PD1 immunotherapy survival after progression on frontline regimens. Finally, enhancing APOE expression via pharmacologic activation of liver X receptors, previously shown to boost anti-tumor immunity(4), exhibited therapeutic efficacy in APOE4 mice but not in APOE2 mice. These findings demonstrate that pre-existing hereditary genetics can impact progression and survival outcomes of a future malignancy and warrant prospective investigation of APOE genotype as a biomarker for melanoma outcome and therapeutic response.

Although much is known about the interaction of fibrinogen with alpha IIb beta 3, much less is known about the interaction of platelets with cross-linked fibrin. Fibrinogen residue Lys406 plays a vital role in the interaction of fibrinogen with alpha IIb beta 3, but because it participates in fibrin cross-linking, it is not available for interacting with alpha IIb beta 3. We studied the adhesion of platelets and HEK cells expressing normal and constitutively active alpha IIb beta 3 to both immobilized fibrinogen and D-dimer, a proteolytic fragment of cross-linked fibrin, as well as platelet-mediated clot retraction. Nonactivated platelets and HEK cells expressing normal alpha IIb beta 3 adhered to fibrinogen but not D-dimer, whereas activated platelets as well as HEK cells expressing activated alpha IIb beta 3 both bound to D-dimer. Small-molecule antagonists of the alpha IIb beta 3 RGD (Arg-Gly-Asp) binding pocket inhibited adhesion to D-dimer, and an Asp119Ala mutation that disrupts the beta 3 metal ion-dependent adhesion site inhibited alpha IIb beta 3-mediated adhesion to D-dimer. D-dimer and a polyclonal antibody against D-dimer inhibited clot retraction. The monoclonal antibody (mAb) 10E5, directed at alpha IIb and a potent inhibitor of platelet interactions with fibrinogen, did not inhibit the interaction of activated platelets with D-dimer or dot retraction, whereas the mAb 7E3, directed at beta 3, inhibited both phenomena. We conclude that activated, but not nonactivated, alpha IIb beta 3 mediates interactions between platelets and D-dimer, and by extrapolation, to cross-linked fibrin. Although the interaction of alpha IIb beta 3 with D-dimer differs from that with fibrinogen, it probably involves contributions from regions on beta 3 that are close to, or that are affected by, changes in the RGD binding pocket.

Introduction: Despite its limitations, CA125 remains the most widely used biomarker for the diagnosis and treatment monitoring of ovarian cancer. Targeting the unshed portion of serum biomarkers such as CA125/MUC16 may afford more specific imaging and targeting of MUC16-positive tumors in High Grade Serous Ovarian Cancer (HGSOC) patients. Methods: Six monoclonal antibodies raised against the 58 amino acid sequence between the extracellular cleavage site and the transmembrane region of MUC16 were radiolabeled with [Zr-89]Zr4+. The radioimmunoconjugates were evaluated in vitro for molar activities, target binding affinity, cellular internalization and serum stability. In vivo characterization was performed via longitudinal positron emission tomography (PET) imaging and ex vivo biodistribution studies in mice bearing subcutaneous xenografts of SKOV3 cells transfected with the proximal 114 amino-acids of MUC16 carboxy-terminus (SKOV3+). Results: In vitro screening identified 9C9 and 4H11 as the lead antibody candidates based on their comparable binding affinities, serum stability and cellular internalization profiles. Despite an identical molecular footprint for binding to MUC16, [Zr-89]Zr-DFO-4H11 yielded a more favorable in vivo radiopharmacologic profile. Furthermore, a humanized variant of 4H11 capable of binding MUC16 in vitro also yielded excellent in vivo profile in subcutaneous xenograft models of SKOV3+, OVCAR3 tumors and a patient-derived xenograft model representative of HGSOC. Conclusion: Radiopharmacologic screening of antibodies early during their development can provide crucial information pertinent to the in vitro characterization and in vivo pharrnacokinetics. The favorable in vivo profile demonstrated by humanized 4H11 combined with the use of its murine predecessor for immunohistochemical staining of biopsied tumor tissues from HGSOC patients makes a unique pair of antibodies that is poised for clinical translation. (C) 2020 Elsevier Inc. All rights reserved.

Foodborne diseases represent a major risk to public health worldwide. In this study, LPST153, a novelSalmonellalytic phage with halo (indicative of potential depolymerase activity) was isolated by employingSalmonella entericaserovar Typhimurium ATCC 13311 as the host and had excellent lytic potential againstSalmonella. LPST153 is effectively able to lyse most prevalent tested serotypes ofSalmonella, includingS.Typhimurium,S.Enteritidis,S.Pullorum andS.Gallinarum. Morphological analysis revealed that phage LPST153 belongs toPodoviridaefamily andCaudoviralesorder and could completely prevent host bacterial growth within 9 h at multiplicity of infection (MOI) of 0.1, 1, 10 and 100. LPST153 had a latent period of 10 min and a burst size of 113 +/- 8 PFU/cell. Characterization of the phage LPST153 revealed that it would be active and stable in some harsh environments or in different conditions of food processing and storage. After genome sequencing and phylogenetic analysis, it is confirmed that LPST153 is a new member of theTeseptimavirusgenus ofAutographivirinaesubfamily. Further application experiments showed that this phage has potential in controllingSalmonellain milk and sausage. LPST153 was also able to inhibit the formation of biofilms and it had the ability to reduce and kill bacteria from inside, including existing biofilms. Therefore, the phage LPST153 could be used as a potential antibacterial agent forSalmonellacontrol in the food industry.