Antibody-mediated spike activation promotes cell-cell transmission of SARS-CoV-2.

The COVID pandemic fueled by emerging SARS-CoV-2 new variants of concern remains a major global health concern, and the constantly emerging mutations present challenges to current therapeutics. The spike glycoprotein is not only essential for the initial viral entry, but is also responsible for the transmission of SARS-CoV-2 components via syncytia formation. Spike-mediated cell-cell transmission is strongly resistant to extracellular therapeutic and convalescent antibodies via an unknown mechanism. Here, we describe the antibody-mediated spike activation and syncytia formation on cells displaying the viral spike. We found that soluble antibodies against receptor binding motif (RBM) are capable of inducing the proteolytic processing of spike at both the S1/S2 and S2' cleavage sites, hence triggering ACE2-independent cell-cell fusion. Mechanistically, antibody-induced cell-cell fusion requires the shedding of S1 and exposure of the fusion peptide at the cell surface. By inhibiting S1/S2 proteolysis, we demonstrated that cell-cell fusion mediated by spike can be re-sensitized towards antibody neutralization in vitro. Lastly, we showed that cytopathic effect mediated by authentic SARS-CoV-2 infection remain unaffected by the addition of extracellular neutralization antibodies. Hence, these results unveil a novel mode of antibody evasion and provide insights for antibody selection and drug design strategies targeting the SARS-CoV-2 infected cells.

Biochemical Characterization and Function of Eight Microbial Type Terpene Synthases from Lycophyte Selaginella moellendorffii.

Selaginella moellendorffii is a lycophyte, a member of an ancient vascular plant lineage. Two distinct types of terpene synthase (TPS) genes were identified from this species, including S. moellendorffii TPS genes (SmTPSs) and S. moellendorffii microbial TPS-like genes (SmMTPSLs). The goal of this study was to investigate the biochemical functions of SmMTPSLs. Here, eight full-length SmMTPSL genes (SmMTPSL5, -15, -19, -23, -33, -37, -46, and -47) were functionally characterized from S. moellendorffii. Escherichia coli-expressed recombinant SmMTPSLs were tested for monoterpenes synthase and sesquiterpenes synthase activities. These enzymatic products were typical monoterpenes and sesquiterpenes that have been previous shown to be generated by typical plant TPSs when provided with geranyl diphosphate (GPP) and farnesyl diphosphate (FPP) as the substrates. Meanwhile, SmMTPSL23, -33, and -37 were up-regulated when induced by alamethicin (ALA) and methyl jasmonate (MeJA), suggesting a role for these genes in plants response to abiotic stresses. Furthermore, this study pointed out that the terpenoids products of SmMTPSL23, -33, and -37 have an antibacterial effect on Pseudomonas syringae pv. tomato DC3000 and Staphylococcus aureus. Taken together, these results provide more information about the catalytic and biochemical function of SmMTPSLs in S. moellendorffii plants.

Removal of black carbon particles from experimental flue gas by surfactant solution in a new type of umbrella plate scrubber.

Black carbon (BC) particles were removed from experimental flue gas by the surfactant solutions of sodium dodecylbenzene sulfonate (SDBS), hexadecyl trimethyl ammonium bromide (CTAB), fatty alcohol polyoxyethylene ether-9 (AEO-9) and polyoxy ethrlene nonyl phinyl ether-10 (TX-10), as well as AEO-9-SDBS, AEO-9-CTAB and SDBS-CTAB, in a new type of umbrella plate scrubber. Among the four independent surfactants, AEO-9 has the lowest surface tension, 35.9 mN/m, which resulted in the highest BC removal ratio among the alone surfactants. The experimental conditions were as follows: dust concentration = 3000 mg/m3; gas velocity = 14 m/s; liquid-gas ratio = 0.80 l/m3; and gas flow = 400 m3/h. When the mole ratio of the mixed surfactants was 1:1, the lowest surface tension could be detected among the studied mixed surfactants. According to the molecular interaction parameters (beta) and the mole ratio of surfactant 1 in the mixture (x1), the synergistic effects of AEO-9-SDBS and SDBS-CTAB solutions were obviously higher than those of AEO-9-TX-10 and AEO-9-CTAB. Therefore, AEO-9-SDBS solution had the lowest surface tension among the mixtures due to its beta < 0 and x1 = 0.85. The mixture solution of AEO-9-SDBS (1:1 mole ratio, 0.2 mmol/l) yielded the highest BC removal ratio, about 99.8%, and it was about 12% higher than that of only water, which was about 87.9%. The calculated critical micelle concentration was almost the same as that of the experimental concentration when the related equation was corrected by beta.

Iron, lanthanum and manganese oxides loaded on gamma-AI2O3 for selective catalytic reduction of NO with NH3 at low temperature.

A series of Mn/Al2O3, La-Mn/Al2O3 and Fe-La-Mn/Al2O3 catalysts were prepared by an impregnation method and investigated for selective catalytic reduction of NO with NH3 at low temperature. The experimental results revealed that NO conversion over La-Mn/Al2O3 was obviously improved after La doping. Addition of Fe increased both NO conversion and the resistance to H2O and SO2. The catalyst Fe0.04La0.03Mn0.06/Al2O3 with a load mass of MnO2 = 6%, La2O3 = 3% and Fe2O3 = 4% exhibited relatively high catalytic activity and yielded 98% NO conversion at 260 degrees with a space velocity of 15,000 h(-1). Meanwhile, the catalytic activity was slightly decreased in the presence of H2O and SO2. Moreover, the catalysts were characterized by N2 adsorption measurement, X-ray diffraction and X-ray photoelectron spectroscopy. The results showed that the doping of La enhanced the dispersion and oxidation states of Mn on the surface of Al2O3. On the surface of the Fe0.04La0.03Mn0.06/Al2O3 catalyst, La was highly dispersed and a mixed oxidation state of Mn existed, while iron ions were only in the Fe3+ state. The mechanism of selective catalytic reduction over these catalysts is also discussed. In this experiment, metal oxides loaded on the support were catalytic centres which served as electron transfer during NO reduction. The electron transfer between Mn3+ and Fe3+ might also exist and the mixture oxidation states of Mn on the surface of the Fe0.04La0.03Mn0.06/Al2O3 catalyst contributed to the SCR activity.

Adsorption mechanism of sodium dodecyl benzene sulfonate on carbon blacks by adsorption isotherm and zeta potential determinations.

Surfactant solutions were propounded to remove fine and hydrophobic carbon black particles from coal-fired flue gas. The adsorption mechanisms between sodium dodecyl benzene sulfonate (SDBS, an anionic surfactant) and carbon black particles in suspension were investigated. The influence of inorganic salt (NaCl) was also considered. As results showed, hydrophobic interactions contributed to the strong adsorption between SDBS and carbon black particles in the absence of NaCl, and adding NaCl affected the adsorption process. The adsorption amount of SDBS significantly increased when NaCl was added into the SDBS solution; however, when SDBS was in low concentration, the amount of adsorbed SDBS, which was responsible for the shift of zeta potentials, varied little under different concentrations of NaCl. This indicated that the adsorption of SDBS was mainly caused by hydrophobic interaction and Na+ could not change the adsorption of SDBS on adsorption site when SDBS was in low concentration. Moreover, the adsorbed SDBS and Na+ were retained in the Stern layer.

miR-199b-5p-AKAP1-DRP1 Pathway Plays a Key Role in ox-LDL-induced Mitochondrial Fission and Endothelial Apoptosis.

BACKGROUND: Atherosclerosis (AS) remains prevalent despite hyperlipidemia-lowering therapies. Although multiple functions of miR-199b-5p have been implicated in cancers, its role in endothelial apoptosis and AS remains unclear. This study aimed to examine the role of miR-199b-5p in mitochondrial dynamics and endothelial apoptosis. METHODS: Human umbilical vein endothelial cells (HUVECs) treated with oxidized low-density lipoprotein (ox-LDL) were subjected to other treatments, followed by a series analysis. We found that ox-LDL-treated HUVECs were associated with miR-199b-5p downregulation, increased reactive oxygen species level, reduced adenosine triphosphate (ATP) production, mitochondrial fission, and apoptosis, whereas enhanced miR-199b-5p expression or applied mitochondrial division inhibitor 1 (Mdivi-1) markedly reversed these changes. RESULTS: Mechanistically, A-kinase anchoring protein 1 (AKAP1) was confirmed as a downstream target of miR-199b-5p by dual-luciferase activity reporter assay. AKAP1 overexpression reversed the anti-apoptotic effects of miR-199b-5p through the enhanced interaction of AKAP1 and dynamin protein 1 (DRP1) in ox-LDL-treated HUVECs. Moreover, miR-199b-5p downregulation, AKAP1 upregulation, and excessive mitochondrial fission were verified in human coronary AS endothelial tissues. CONCLUSION: The miR-199b-5p-dependent regulation of AKAP1/DRP1 is required to inhibit hyperlipidemia- induced mitochondrial fission and endothelial injury and may be a promising therapeutic target for AS.

Biochemical and functional characterization of two microbial type terpene synthases from moss Stereodon subimponens.

Terpenes constitute a large class of plant secondary metabolites. Usually, there is only one type of terpene synthase in seed plants, which is called typical plant terpene synthase. Currently, as a new family of plant terpene synthases, microbial terpene synthase-like (MTPSL) is identificated in nonseed plants. However, our knowledge about the biological function of most MTPSLs in nonseed plants is very limited. Here, we investigated the biochemical and functional characterization of the enzymes encoded by two MTPSLs from moss Stereodon subimponens, SsMTPSL1 and SsMTPSL2. A phylogenetic tree analysis showed that SsMTPSL1 and SsMTPSL2 are homologous to AaMTPSL1, AaMTPSL3, ApMTPSL1, and ApMTPSL3 from hornworts. The enzyme activity experiment demonstrated that SsMTPSL1 has monoterpene synthase and sesquiterpene synthase activity, and SsMTPSL2 has monoterpene synthase activity. Next, we selected SsMTPSL1 to study its biochemical functions. Anti-bacterial activity test in vitro showed that the products of SsMTPSL1 have an anti-bacterial effect on Escherichia coli, Pseudomonas syringae pv. Tomato DC3000 (Pst DC3000), and Staphylococcus aureus. To further understand the function of SsMTPSL1, the transgenic Arabidopsis thaliana plant of SsMTPSL1 is inoculated by Pst DC3000, and the result showed that SsMTPSL1 enhances the resistance of A. thaliana to Pst DC3000. All in all, this study provides new information about the functions of moss MTPSLs.

Uncovering a conserved vulnerability site in SARS-CoV-2 by a human antibody.

An essential step for SARS-CoV-2 infection is the attachment to the host cell receptor by its Spike receptor-binding domain (RBD). Most of the existing RBD-targeting neutralizing antibodies block the receptor-binding motif (RBM), a mutable region with the potential to generate neutralization escape mutants. Here, we isolated and structurally characterized a non-RBM-targeting monoclonal antibody (FD20) from convalescent patients. FD20 engages the RBD at an epitope distal to the RBM with a KD of 5.6 nM, neutralizes SARS-CoV-2 including the current Variants of Concern such as B.1.1.7, B.1.351, P.1, and B.1.617.2 (Delta), displays modest cross-reactivity against SARS-CoV, and reduces viral replication in hamsters. The epitope coincides with a predicted "ideal" vulnerability site with high functional and structural constraints. Mutation of the residues of the conserved epitope variably affects FD20-binding but confers little or no resistance to neutralization. Finally, in vitro mode-of-action characterization and negative-stain electron microscopy suggest a neutralization mechanism by which FD20 destructs the Spike. Our results reveal a conserved vulnerability site in the SARS-CoV-2 Spike for the development of potential antiviral drugs.

A synthetic nanobody targeting RBD protects hamsters from SARS-CoV-2 infection.

SARS-CoV-2, the causative agent of COVID-191, features a receptor-binding domain (RBD) for binding to the host cell ACE2 protein1-6. Neutralizing antibodies that block RBD-ACE2 interaction are candidates for the development of targeted therapeutics7-17. Llama-derived single-domain antibodies (nanobodies, ~15 kDa) offer advantages in bioavailability, amenability, and production and storage owing to their small sizes and high stability. Here, we report the rapid selection of 99 synthetic nanobodies (sybodies) against RBD by in vitro selection using three libraries. The best sybody, MR3 binds to RBD with high affinity (KD = 1.0 nM) and displays high neutralization activity against SARS-CoV-2 pseudoviruses (IC50 = 0.42 µg mL-1). Structural, biochemical, and biological characterization suggests a common neutralizing mechanism, in which the RBD-ACE2 interaction is competitively inhibited by sybodies. Various forms of sybodies with improved potency have been generated by structure-based design, biparatopic construction, and divalent engineering. Two divalent forms of MR3 protect hamsters from clinical signs after live virus challenge and a single dose of the Fc-fusion construct of MR3 reduces viral RNA load by 6 Log10. Our results pave the way for the development of therapeutic nanobodies against COVID-19 and present a strategy for rapid development of targeted medical interventions during an outbreak.

Research on soot of black smoke from ceramic furnace flue gas: characterization of soot.

In this study, the characterizations of soot from ceramic furnace flue gas were studied using environmental scanning electron microscopy, energy dispersive spectroscopy, particle size distribution, specific surface area measurements, crystal characterizations and organic pollutant analysis. Soot particles were mainly spherical nanoparticles with diameters less than 100 nm. However, the particles could be aggregated into larger ones with a median diameter of 3.66 µm. Nanometer pores with diameters ranging 2-4 nm were also detected in the soot particles. Because of their large surface areas and pore volumes, other pollutants in the environment can be adsorbed to soot particles potentially making them more hazardous. Several elements, including C, O and Pb, were detected in the soot, but only small amounts of crystalline materials were observed. This is because most of the detected carbon and metals/metal oxides/metal salts were amorphous. Approximately 90 different organic pollutants were detected in the soot, including aromatic compounds and other hydrocarbons. Because of the carcinogenic properties of aromatic compounds and the photochemical effects of hydrocarbons, soot could have serious health and environmental impacts. The results suggest that soot particles are hazardous material and urgently need to be controlled.

[Color Doppler ultrasonic measurements of normal mesenteric lymph nodes in healthy children].

OBJECTIVE: To assess the value of color Doppler ultrasound in evaluating the mesenteric lymph nodes in healthy children. METHODS: The mesenteric lymph nodes were examined with color Doppler ultrasonography for 730 randomly selected healthy children under 14 years of age, including 410 boys and 298 girls who did not report any recent medical conditions. RESULTS: Abdominal lymph node detection rate was higher in boys than in girls. Abdominal lymph nodes were detected most often in children between the ages of 1 and 4 years, and the lymph node size decreased gradually with age. CONCLUSION: Color Doppler ultrasonography is valuable for evaluating abdominal lymph nodes in children.

Study on activated carbon derived from sewage sludge for adsorption of gaseous formaldehyde.

The aim of this work is to evaluate the adsorption performances of activated carbon derived from sewage sludge (ACSS) for gaseous formaldehyde removal compared with three commercial activated carbons (CACs) using self-designing adsorption and distillation system. Formaldehyde desorption of the activated carbons for regeneration was also studied using thermogravimetric (TG) analysis. The porous structure and surface characteristics were studied using N2 adsorption and desorption isotherms, scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR). The results show that ACSS has excellent adsorption performance, which is overall superior to the CACs. Adsorption theory indicates that the ACSS outperforms the CACs due to its appropriate porous structure and surface chemistry characteristics for formaldehyde adsorption. The TG analysis of desorption shows that the optimum temperature to regenerate ACSS is 75°C, which is affordable and economical for recycling.

[Enlarged mesenteric lymph nodes in children: a clinical analysis with ultrasonography and the implications].

OBJECTIVE: To compare the enlarged mesenteric lymph nodes in healthy children with those children with mesenteric lymphadenitis. METHODS: According to the diagnostic criteria defining lymph node enlargement as a 5-mm enlargement or greater in the short diameter, 137 healthy children and 148 children with mesenteric lymphadenitis were retrospectively analyzed for mesenteric lymph node enlargement based on the ultrasonographic data. RESULTS: The distribution of enlarged mesenteric lymph nodes was detected in the right lower quadrant (RLQ) in 46.3%, in the para-aortic areas in 19.2%, and in the left lower quadrant (LLQ) in 13.6% of the children. The clusters of lymph nodes between the two groups showed no significant difference in the distribution, age, L/W, longitudinal diameter or clusters, only the short diameter differed significantly between them. CONCLUSION: Enlarged mesenteric lymph nodes are present in many healthy children, which does not necessarily suggests any abnormalities. The mesenteric lymph nodes increase with the age until 6 years and then decrease. The lymph nodes with a short diameter larger than 8 mm may indicate the condition of mesenteric lymphadenitis.