Coronavirus disease 2019 (COVID-19) is an ongoing pandemic that lacks effective therapeutic interventions. SARS-CoV-2 infects ACE2-expressing cells and gains cell entry through either direct plasma ...membrane fusion or endocytosis. Recent studies have shown that in addition to ACE2, heparan sulfate proteoglycans (HSPGs) also play an important role in SARS-CoV-2 cell attachment by serving as an attachment factor. Binding of viral spike protein to HSPGs leads to the enrichment of local concentration for the subsequent specific binding with ACE2. We therefore hypothesize that blocking the interactions between viral spike protein and the HSPGs will lead to inhibition of viral replication. In this study, we report our findings of the broad-spectrum antiviral activity and the mechanism of action of lactoferrin (LF) against multiple common human coronaviruses as well as SARS-CoV-2. Our study has shown that LF has broad-spectrum antiviral activity against SARS-CoV-2, HCoV-OC43, HCoV-NL63, and HCoV-229E in cell culture, and bovine lactoferrin (BLF) is more potent than human lactoferrin. Mechanistic studies revealed that BLF binds to HSPGs, thereby blocking viral attachment to the host cell. The antiviral activity of BLF can be antagonized by the HSPG mimetic heparin. Combination therapy experiment showed that the antiviral activity of LF is synergistic with remdesivir in cell culture. Molecular modelling suggests that the N-terminal positively charged region in BLF (residues 17-41) confers the binding to HSPGs. Overall, LF appears to be a promising drug candidate for COVID-19 that warrants further investigation.
The main protease (M
) of SARS-CoV-2 is a validated antiviral drug target. Several M
inhibitors have been reported with potent enzymatic inhibition and cellular antiviral activity, including
,
,
, ...and
, with each containing a reactive warhead that covalently modifies the catalytic Cys145. Coupling structure-based drug design with the one-pot Ugi four-component reaction, we discovered one of the most potent noncovalent inhibitors,
(
) that is structurally distinct from the canonical M
inhibitor
. Significantly,
is highly selective compared with covalent inhibitors such as
, especially toward host proteases. The cocrystal structure of SARS-CoV-2 M
with
revealed a previously unexplored binding site located in between the S2 and S4 pockets. Overall, this study discovered
, one of the most potent and selective noncovalent SARS-CoV-2 M
inhibitors reported to date, and a novel binding pocket in M
that can be explored for inhibitor design.
A compact frequency reconfigurable beam switching antenna based on a single‐layer frequency selective face (FSS) is proposed in this paper. The proposed antenna consists of a dual‐band dipole antenna ...and a single‐layer FSS with hexagonally arrangement. The omnidirectional radiation pattern of the dipole antenna designed as a radiation source and surrounded by the FSS can be converted into directional radiation pattern sweeping along the entire azimuthal plane at two single frequency of 2.4 or 5 GHz. The frequency selection is achieved by controlling the diode state of the FSS unit, and the beam switching is realised by a specific combination of electromagnetic wave reflection or transmission from the hexagonal FSS. The novelty lies in applying the hexagonal arrangement to a dual single‐frequency single‐layer FSS unit. This will not destroy the reflection or transmission characteristics of the FSS unit, but also contribute to reduce the antenna size and achieve a low cost. To validate the design, a prototype is fabricated and measured. The single‐layer FSS antenna with a volume of 57 mm × 57 mm × 58.5 mm can be scanned in 12 steps along the azimuth plane at 2.4 and 5 GHz, respectively.
The omnidirectional radiation pattern of the dipole antenna designed as a radiation source and surrounded by the FSS can be converted into directional radiation pattern sweeping along the entire azimuthal plane at two single frequency of 2.4 or 5 GHz.The novelty lies in applying the hexagonal arrangement to a dual single‐frequency single‐layer FSS unit.
The papain-like protease (PLpro) of SARS-CoV-2 is a validated antiviral drug target. Through a fluorescence resonance energy transfer-based high-throughput screening and subsequent lead optimization, ...we identified several PLpro inhibitors including Jun9-72-2 and Jun9-75-4 with improved enzymatic inhibition and antiviral activity compared to GRL0617, which was reported as a SARS-CoV PLpro inhibitor. Significantly, we developed a cell-based FlipGFP assay that can be applied to predict the cellular antiviral activity of PLpro inhibitors in the BSL-2 setting. X-ray crystal structure of PLpro in complex with GRL0617 showed that binding of GRL0617 to SARS-CoV-2 induced a conformational change in the BL2 loop to a more closed conformation. Molecular dynamics simulations showed that Jun9-72-2 and Jun9-75-4 engaged in more extensive interactions than GRL0617. Overall, the PLpro inhibitors identified in this study represent promising candidates for further development as SARS-CoV-2 antivirals, and the FlipGFP-PLpro assay is a suitable surrogate for screening PLpro inhibitors in the BSL-2 setting.
The discovery of an emerging viral disease, severe fever with thrombocytopenia syndrome (SFTS), caused by SFTS virus (SFTSV), has prompted the need to understand pathogenesis of SFTSV. We are unique ...in establishing an infectious model of SFTS in C57/BL6 mice, resulting in hallmark symptoms of thrombocytopenia and leukocytopenia. Viral RNA and histopathological changes were identified in the spleen, liver, and kidney. However, viral replication was only found in the spleen, which suggested the spleen to be the principle target organ of SFTSV. Moreover, the number of macrophages and platelets were largely increased in the spleen, and SFTSV colocalized with platelets in cytoplasm of macrophages in the red pulp of the spleen. In vitro cellular assays further revealed that SFTSV adhered to mouse platelets and facilitated the phagocytosis of platelets by mouse primary macrophages, which in combination with in vivo findings, suggests that SFTSV-induced thrombocytopenia is caused by clearance of circulating virus-bound platelets by splenic macrophages. Thus, this study has elucidated the pathogenic mechanisms of thrombocytopenia in a mouse model resembling human SFTS disease.
SAMD9 and SAMD9L (SAMD9/9L) are antiviral factors and tumor suppressors, playing a critical role in innate immune defense against poxviruses and the development of myeloid tumors. SAMD9/9L mutations ...with a gain-of-function (GoF) in inhibiting cell growth cause multisystem developmental disorders including many pediatric myelodysplastic syndromes. Predicted to be multidomain proteins with an architecture like that of the NOD-like receptors, SAMD9/9L molecular functions and domain structures are largely unknown. Here, we identified a SAMD9/9L effector domain that functions by binding to double-stranded nucleic acids (dsNA) and determined the crystal structure of the domain in complex with DNA. Aided with precise mutations that differentially perturb dsNA binding, we demonstrated that the antiviral and antiproliferative functions of the wild-type and GoF SAMD9/9L variants rely on dsNA binding by the effector domain. Furthermore, we showed that GoF variants inhibit global protein synthesis, reduce translation elongation, and induce proteotoxic stress response, which all require dsNA binding by the effector domain. The identification of the structure and function of a SAMD9/9L effector domain provides a therapeutic target for SAMD9/9L-associated human diseases.
Host restriction factors constitute a formidable barrier for viral replication to which many viruses have evolved counter-measures. Human SAMD9, a tumor suppressor and a restriction factor for ...poxviruses in cell lines, is antagonized by two classes of poxvirus proteins, represented by vaccinia virus (VACV) K1 and C7. A paralog of SAMD9, SAMD9L, is also encoded by some mammals, while only one of two paralogs is retained by others. Here, we show that SAMD9L functions similarly to SAMD9 as a restriction factor and that the two paralogs form a critical host barrier that poxviruses must overcome to establish infection. In mice, which naturally lack SAMD9, overcoming SAMD9L restriction with viral inhibitors is essential for poxvirus replication and pathogenesis. While a VACV deleted of both K1 and C7 (vK1L-C7L-) was restricted by mouse cells and highly attenuated in mice, its replication and virulence were completely restored in SAMD9L-/- mice. In humans, both SAMD9 and SAMD9L are poxvirus restriction factors, although the latter requires interferon induction in many cell types. While knockout of SAMD9 with Crispr-Cas9 was sufficient for abolishing the restriction for vK1L-C7L- in many human cells, knockout of both paralogs was required for abolishing the restriction in interferon-treated cells. Both paralogs are antagonized by VACV K1, C7 and C7 homologs from diverse mammalian poxviruses, but mouse SAMD9L is resistant to the C7 homolog encoded by a group of poxviruses with a narrow host range in ruminants, indicating that host species-specific difference in SAMD9/SAMD9L genes serves as a barrier for cross-species poxvirus transmission.
We present the design and experimental demonstration of a programmable subwavelength coil array, which can manipulate the evanescent magnetic field leading to a precisely controlled electric-field ...pattern at an image plane in the near-field zone. A synthesis methodology is outlined for 2-D near-field manipulations. Simulation based on a full-wave electromagnetic solver clearly demonstrates the focused electric-field pattern, and its implementation is discussed. An example of a three-layer subwavelength coil array with 48 units is fabricated and measured. The consensus of the measured results with the simulated and synthesized results verified the presented synthesis method. Such a device, capable of producing a programmable magnetic field and electric field, respectively, in orthogonal planes, will find applications in biomedical devices such as neural stimulation, and potentially other areas such as noncontact charging.
Tailing cement filling is an important development direction in mine filling, as it is a green and environmentally friendly method for efficiently treating solid waste in mines. Adding a certain ...amount of waste rock can effectively improve the backfill strength and better meet the filling strength requirements. To address the use of waste rock tailings in cemented filling materials, a uniaxial compression test was carried out on backfills with different cement/sand ratios and waste rock contents, and the influence of the cement/sand ratio and waste rock content on the strength of the backfill was studied. This study found that when the waste rock content is certain, the strength of the backfill increases with the increase in the cement/sand ratio, and the increase in strength slows with the increase in the cement/sand ratio until the strength of the backfill reaches a limit and no longer increases. When the cement/sand ratio is constant, the strength of the backfill first increases and then decreases as the waste rock content increases. When the cement content is constant, the addition of a certain amount of waste rock reduces the specific surface area of the solid materials in the backfill, increases the amount of cement per unit area, and improves the strength of the backfill. When the waste rock content is too high, due to the large particle size of the waste rock, the tailings cannot completely wrap around the waste rock, resulting in a weakening of the cement in the backfill, which reduces the strength of the backfill. This study found that the waste rock content and the cement/sand ratio in the backfill have a significant impact on backfill damage. The damage is mainly caused by insufficient cement strength. The presence of waste rock will change the original direction of crack propagation, resulting in more crack bifurcation, and the form of the destruction surface on the backfill is complicated and diverse.
Cellular membranes are maintained as closed compartments, broken up only transiently during membrane reorganization or lipid transportation. However, open-ended membranes, likely derived from ...scissions of the endoplasmic reticulum, persist in vaccinia virus-infected cells during the assembly of the viral envelope. A group of viral membrane assembly proteins (VMAPs) were identified as essential for this process. To understand the mechanism of VMAPs, we determined the 2.2-Å crystal structure of the largest member, named A6, which is a soluble protein with two distinct domains. The structure of A6 displays a novel protein fold composed mainly of alpha helices. The larger C-terminal domain forms a unique cage that encloses multiple glycerophospholipids with a lipid bilayer-like configuration. The smaller N-terminal domain does not bind lipid but negatively affects lipid binding by A6. Mutations of key hydrophobic residues lining the lipid-binding cage disrupt lipid binding and abolish viral replication. Our results reveal a protein modality for enclosing the lipid bilayer and provide molecular insight into a viral machinery involved in generating and/or stabilizing open-ended membranes.
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