Enterovirus 71 (EV71), a major agent of hand-foot-and-mouth disease in children, can cause severe central nervous system disease and mortality. At present no vaccine or antiviral therapy is available. We have determined high-resolution structures for the mature virus and natural empty particles. The structure of the mature virus is similar to that of other enteroviruses, whilst the empty particles are dramatically expanded, with notable fissures, resembling elusive enterovirus uncoating intermediates not previously characterized in atomic detail. Hydrophobic capsid pockets within the EV71 capsid are collapsed in this expanded particle, providing a detailed explanation of the mechanism for receptor-binding triggered virus uncoating. The results provide a paradigm for enterovirus uncoating, in which the VP1 GH loop acts as an adaptor-sensor for the attachment of cellular receptors, converting heterologous inputs to a generic uncoating mechanism, spotlighting novel points for therapeutic intervention.

Background Although several COVID-19 vaccines have been developed so far, they will not be sufficient to meet the global demand. Development of a wider range of vaccines, with different mechanisms of action, could help control the spread of SARS-CoV-2 globally. We developed a protein subunit vaccine against COVID-19 using a dimeric form of the receptor-binding domain (RBD) of the SARS-CoV-2 spike protein as the antigen. We aimed to assess the safety and immunogenicity of this vaccine, ZF2001, and determine the appropriate dose and schedule for an efficacy study. Methods We did two randomised, double-blind, placebo-controlled, phase 1 and phase 2 trials. Phase 1 was done at two university hospitals in Chongqing and Beijing, China, and phase 2 was done at the Hunan Provincial Center for Disease Control and Prevention in Xiangtan, China. Healthy adults aged 18–59 years, without a history of SARS-CoV or SARS-CoV-2 infection, an RT-PCR-positive test result for SARS-CoV-2, a history of contact with confirmed or suspected COVID-19 cases, and severe allergies to any component of the vaccine were eligible for enrolment. In phase 1, participants were randomly assigned (2:2:1) to receive three doses of the vaccine (25 μg or 50 μg) or placebo intramuscularly, 30 days apart. In phase 2, participants were randomly assigned (1:1:1:1:1:1) to receive the vaccine (25 μg or 50 μg) or placebo intramuscularly, 30 days apart, in either a two-dose schedule or a three-dose schedule. Investigators, participants, and the laboratory team were masked to group allocation. For phase 1, the primary outcome was safety, measured by the occurrence of adverse events and serious adverse events. For phase 2, the primary outcome was safety and immunogenicity (the seroconversion rate and the magnitude, in geometric mean titres [GMTs], of SARS-CoV-2-neutralising antibodies). Analyses were done on an intention-to-treat and per-protocol basis. These trials are registered with ClinicalTrials.gov ( NCT04445194 and NCT04466085 ) and participant follow-up is ongoing. Findings Between June 22 and July 3, 2020, 50 participants were enrolled into the phase 1 trial and randomly assigned to receive three doses of placebo (n=10), the 25 μg vaccine (n=20), or the 50 μg vaccine (n=20). The mean age of participants was 32·6 (SD 9·4) years. Between July 12 and July 17, 2020, 900 participants were enrolled into the phase 2 trial and randomly assigned to receive two doses of placebo (n=150), 25 μg vaccine (n=150), or 50 μg vaccine (n=150), or three doses of placebo (n=150), 25 μg vaccine (n=150), or 50 μg vaccine (n=150). The mean age of participants was 43·5 (SD 9·2) years. In both phase 1 and phase 2, adverse events reported within 30 days after vaccination were mild or moderate (grade 1 or 2) in most cases (phase 1: six [60%] of ten participants in the placebo group, 14 [70%] of 20 in the 25 μg group, and 18 [90...

Using the scanning ion-selective electrode technique, fluxes of H+, Na+, and Cl− were investigated in roots and derived protoplasts of salt-tolerant Populus euphratica and salt-sensitive Populus popularis 35-44 (P. popularis). Compared to P. popularis, P. euphratica roots exhibited a higher capacity to extrude Na+ after a short-term exposure to 50 mm NaCl (24 h) and a long term in a saline environment of 100 mm NaCl (15 d). Root protoplasts, isolated from the long-term-stressed P. euphratica roots, had an enhanced Na+ efflux and a correspondingly increased H+ influx, especially at an acidic pH of 5.5. However, the NaCl-induced Na+/H+ exchange in root tissues and cells was inhibited by amiloride (a Na+/H+ antiporter inhibitor) or sodium orthovanadate (a plasma membrane H+-ATPase inhibitor). These results indicate that the Na+ extrusion in stressed P. euphratica roots is the result of an active Na+/H+ antiport across the plasma membrane. In comparison, the Na+/H+ antiport system in salt-stressed P. popularis roots was insufficient to exclude Na+ at both the tissue and cellular levels. Moreover, salt-treated P. euphratica roots retained a higher capacity for Cl− exclusion than P. popularis, especially during a long term in high salinity. The pattern of NaCl-induced fluxes of H+, Na+, and Cl− differs from that caused by isomotic mannitol in P. euphratica roots, suggesting that NaCl-induced alternations of root ion fluxes are mainly the result of ion-specific effects.

It remains largely mysterious how the genomes of non-enveloped eukaryotic viruses are transferred across a membrane into the host cell. Picornaviruses are simple models for such viruses, and initiate this uncoating process through particle expansion, which reveals channels through which internal capsid proteins and the viral genome presumably exit the particle, although this has not been clearly seen until now. Here we present the atomic structure of an uncoating intermediate for the major human picornavirus pathogen CAV16, which reveals VP1 partly extruded from the capsid, poised to embed in the host membrane. Together with previous low-resolution results, we are able to propose a detailed hypothesis for the ordered egress of the internal proteins, using two distinct sets of channels through the capsid, and suggest a structural link to the condensed RNA within the particle, which may be involved in triggering RNA release.

In the past few decades, hundreds of materials have been tried as adjuvant; however, only aluminum-based adjuvants continue to be used widely in the world. Aluminum hydroxide, aluminum phosphate and alum constitute the main forms of aluminum used as adjuvants. Among these, aluminum hydroxide is the most commonly used chemical as adjuvant. In spite of its wide spread use, surprisingly, the mechanism of how aluminum hydroxide-based adjuvants exert their beneficial effects is still not fully understood. Current explanations for the mode of action of aluminum hydroxide-based adjuvants include, among others, the repository effect, pro-phagocytic effect, and activation of the pro-inflammatory NLRP3 pathway. These collectively galvanize innate as well as acquired immune responses and activate the complement system. Factors that have a profound influence on responses evoked by aluminum hydroxide-based adjuvant applications include adsorption rate, strength of the adsorption, size and uniformity of aluminum hydroxide particles, dosage of adjuvant, and the nature of antigens. Although vaccines containing aluminum hydroxide-based adjuvants are beneficial, sometimes they cause adverse reactions. Further, these vaccines cannot be stored frozen. Until recently, aluminum hydroxide-based adjuvants were known to preferentially prime Th2-type immune responses. However, results of more recent studies show that depending on the vaccination route, aluminum hydroxide-based adjuvants can enhance both Th1 as well as Th2 cellular responses. Advances in systems biology have opened up new avenues for studying mechanisms of aluminum hydroxide-based adjuvants. These will assist in scaling new frontiers in aluminum hydroxide-based adjuvant research that include improvement of formulations, use of nanoparticles of aluminum hydroxide and development of composite adjuvants.

Hepatitis A virus (HAV) remains enigmatic, despite some 1.4 million cases worldwide annually1. It differs radically from other picornaviruses, existing in an enveloped form2 and being unusually stable, both genetically and physically3, but has proved difficult to study. We report high-resolution X-ray structures for the mature virus and empty particles. The structures of the two particles are indistinguishable, apart from some disorder on the inside of the empty particle. The full virus contains the small viral protein VP4, while the empty particle harbors only the uncleaved precursor, VP0. The smooth particle surface is devoid of depressions which might correspond to receptor binding sites. Peptide scanning data extends the previously reported VP3 antigenic site4, while structure-based predictions5 suggest further epitopes. HAV contains no pocket factor, can withstand remarkably high temperature and low pH, with empty particles being even more robust than full particles. The virus probably uncoats via a novel mechanism, being built differently to other picornaviruses. It utilizes a VP2 ‘domain swap’ characteristic of insect picorna-like viruses6,7 and structure-based phylogenetic analysis places HAV between typical picornaviruses and the insect viruses. The enigmatic properties of HAV may reflect its position as a link between ‘modern’ picornaviruses and the more ‘primitive’ precursor insect viruses, for instance HAV retains the ability to move from cell-to-cell by transcytosis8,9.

The receptor-interacting kinase-3 (RIP3) and its downstream substrate mixed lineage kinase domain-like protein (MLKL) have emerged as the key cellular components in programmed necrotic cell death. Receptors for the cytokines of tumor necrosis factor (TNF) family and Toll-like receptors (TLR) 3 and 4 are able to activate RIP3 through receptor-interacting kinase-1 and Toll/IL-1 receptor domaincontaining adapter inducing IFN-β, respectively. This form of cell death has been implicated in the host-defense system. However, the molecular mechanisms that drive the activation of RIP3 by a variety of pathogens, other than the above-mentioned receptors, are largely unknown. Here, we report that human herpes simplex virus 1 (HSV-1) infection triggers RIP3-dependent necrosis. This process requires MLKL but is independent of TNF receptor, TLR3, cylindromatosis, and host RIP homotypic interaction motif-containing protein DNA-dependent activator of IFN regulatory factor. After HSV-1 infection, the viral ribonucleotide reductase large subunit (ICP6) interacts with RIP3. The formation of the ICP6-RIP3 complex requires the RHIM domains of both proteins. An HSV-1 ICP6 deletion mutant failed to cause effective necrosis of HSV-1-infected cells. Furthermore, ectopic expression of ICP6, but not RHIM mutant ICP6, directly activated RIP3/MLKL-mediated necrosis. Mice lacking RIP3 exhibited severely impaired control of HSV-1 replication and pathogenesis. Therefore, this study reveals a previously uncharacterized host antipathogen mechanism.programmed necrosis | HSV-1 | ICP6 | RIP3 | MLKL C ell death triggered by pathogens is a crucial component of mammalian host-defense system. Apoptosis, a predominant programmed cell death in mammals, functions as an effective host-defense mechanism for preventing pathogen replication. Apoptosis is initiated by either mitochondria or cell-death receptors, and it is executed by a group of cysteine proteases called caspases (1). The apoptotic pathway can be subverted by pathogen-encoded apoptotic suppressors such as caspase inhibitors (2). Recent studies have revealed that caspase inhibition can lead to alternative activation of necrosis, releasing the damage-associated molecular patterns (DAMPs) signal to trigger the activation of the host immune system (3, 4).Cytokines of the TNF family are classical inducers of programmed necrosis that are morphologically characterized by the swelling of intracellular organelles and disrupted plasma membranes. Programmed necrosis triggered by death cytokines such as TNF, also known as necroptosis (5-7), is tightly regulated by receptor-interacting kinase-1 (RIP1) (8), its deubiquitin enzyme cylindromatosis (CYLD) (9), and receptor-interacting kinase-3 (RIP3) (10-12). The RIP homotypic interaction motif (RHIM) domains of RIP1 and RIP3 are required for the formation of the RIP1-RIP3 complex that is called a necrosome (13). Recently, mixed lineage kinase domain-like (MLKL) protein has been identified as a functional substrate of RIP3 kinase (14, 15). Upon phosphorylation, ...

Using confocal microscopy, X‐ray microanalysis and the scanning ion‐selective electrode technique, we investigated the signalling of H2O2, cytosolic Ca2+ ([Ca2+]cyt) and the PM H+‐coupled transport system in K+/Na+ homeostasis control in NaCl‐stressed calluses of Populus euphratica. An obvious Na+/H+ antiport was seen in salinized cells; however, NaCl stress caused a net K+ efflux, because of the salt‐induced membrane depolarization. H2O2 levels, regulated upwards by salinity, contributed to ionic homeostasis, because H2O2 restrictions by DPI or DMTU caused enhanced K+ efflux and decreased Na+/H+ antiport activity. NaCl induced a net Ca2+ influx and a subsequent rise of [Ca2+]cyt, which is involved in H2O2‐mediated K+/Na+ homeostasis in salinized P. euphratica cells. When callus cells were pretreated with inhibitors of the Na+/H+ antiport system, the NaCl‐induced elevation of H2O2 and [Ca2+]cyt was correspondingly restricted, leading to a greater K+ efflux and a more pronounced reduction in Na+/H+ antiport activity. Results suggest that the PM H+‐coupled transport system mediates H+ translocation and triggers the stress signalling of H2O2 and Ca2+, which results in a K+/Na+ homeostasis via mediations of K+ channels and the Na+/H+ antiport system in the PM of NaCl‐stressed cells. Accordingly, a salt stress signalling pathway of P. euphratica cells is proposed.