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Omicron (B.1.1.529), the most heavily mutated SARS-CoV-2 variant so far, is highly resistant to neutralizing antibodies, raising concerns about the effectiveness of antibody therapies and vaccines1,2. Here we examined whether sera from individuals who received two or three doses of inactivated SARS-CoV-2 vaccine could neutralize authentic Omicron. The seroconversion rates of neutralizing antibodies were 3.3% (2 out of 60) and 95% (57 out of 60) for individuals who had received 2 and 3 doses of vaccine, respectively. For recipients of three vaccine doses, the geometric mean neutralization antibody titre for Omicron was 16.5-fold lower than for the ancestral virus (254). We isolated 323 human monoclonal antibodies derived from memory B cells in triple vaccinees, half of which recognized the receptor-binding domain, and showed that a subset (24 out of 163) potently neutralized all SARS-CoV-2 variants of concern, including Omicron. Therapeutic treatments with representative broadly neutralizing monoclonal antibodies were highly protective against infection of mice with SARS-CoV-2 Beta (B.1.351) and Omicron. Atomic structures of the Omicron spike protein in complex with three classes of antibodies that were active against all five variants of concern defined the binding and neutralizing determinants and revealed a key antibody escape site, G446S, that confers greater resistance to a class of antibodies that bind on the right shoulder of the receptor-binding domain by altering local conformation at the binding interface. Our results rationalize the use of three-dose immunization regimens and suggest that the fundamental epitopes revealed by these broadly ultrapotent antibodies are rational targets for a universal sarbecovirus vaccine.

High-voltage-activated R-type CaV2.3 channel plays pivotal roles in many physiological activities and is implicated in epilepsy, convulsions, and other neurodevelopmental impairments. Here, we determine the high-resolution cryo-electron microscopy (cryo-EM) structure of human CaV2.3 in complex with the α2δ1 and β1 subunits. The VSDIIis stabilized in the resting state. Electrophysiological experiments elucidate that the conformational change of VSDIIin response to variation in membrane potential is not required for channel activation, whereas the other VSDs are essential for channel opening. The intracellular gate is blocked by the W-helix. A pre-W-helix adjacent to the W-helix can significantly regulate closed-state inactivation (CSI) by modulating the association and dissociation of the W-helix with the gate. Electrostatic interactions formed between the negatively charged domain on S6II, which is exclusively conserved in the CaV2 family, and nearby regions at the alpha-interacting domain (AID) and S4-S5IIhelix are identified. Further functional analyses indicate that these interactions are critical for the open-state inactivation (OSI) of CaV2 channels.

SummaryThe SARS-CoV-2 Omicron with increased fitness is spreading rapidly worldwide. Analysis of cryo-EM structures of the Spike (S) from Omicron reveals amino acid substitutions forging new interactions that stably maintain an “active” conformation for receptor recognition. The relatively more compact domain organization confers improved stability and enhances attachment but compromises the efficiency of viral fusion step. Alterations in local conformation, charge and hydrophobic microenvironments underpin the modulation of the epitopes such that they are not recognized by most NTD- and RBD-antibodies, facilitating viral immune escape. Apart from already existing mutations, we have identified three new immune escape sites: 1) Q493R, 2) G446S and 3) S371L/S373P/S375F that confers greater resistance to five of the six classes of RBD-antibodies. Structure of the Omicron S bound with human ACE2, together with analysis of sequence conservation in ACE2 binding region of 25 sarbecovirus members as well as heatmaps of the immunogenic sites and their corresponding mutational frequencies sheds light on conserved and structurally restrained regions that can be used for the development of broad-spectrum vaccines and therapeutics.

The SARS-CoV-2 Omicron variant with increased fitness is spreading rapidly worldwide. Analysis of cryo-EM structures of the spike (S) from Omicron reveals amino acid substitutions forging interactions that stably maintain an active conformation for receptor recognition. The relatively more compact domain organization confers improved stability and enhances attachment but compromises the efficiency of the viral fusion step. Alterations in local conformation, charge, and hydrophobic microenvironments underpin the modulation of the epitopes such that they are not recognized by most NTD- and RBD-antibodies, facilitating viral immune escape. Structure of the Omicron S bound with human ACE2, together with the analysis of sequence conservation in ACE2 binding region of 25 sarbecovirus members, as well as heatmaps of the immunogenic sites and their corresponding mutational frequencies, sheds light on conserved and structurally restrained regions that can be used for the development of broad-spectrum vaccines and therapeutics., Graphical abstract, Mutations in the SARS-CoV-2 Omicron variant improve spike trimer stability that supports viral attachment but appears to compromise viral fusion. They also perturb the confirmation of antigenic sites for antibody recognition, which may contribute to immune evasion.

Omicron, the most heavily mutated SARS-CoV-2 variant so far, is highly resistant to neutralizing antibodies, raising unprecedented concerns about the effectiveness of antibody therapies and vaccines. We examined whether sera from individuals who received two or three doses of inactivated vaccine, could neutralize authentic Omicron. The seroconversion rates of neutralizing antibodies were 3.3% (2/60) and 95% (57/60) for 2- and 3-dose vaccinees, respectively. For three-dose recipients, the geometric mean neutralization antibody titer (GMT) of Omicron was 15, 16.5-fold lower than that of the ancestral virus (254). We isolated 323 human monoclonal antibodies derived from memory B cells in 3-dose vaccinees, half of which recognize the receptor binding domain (RBD) and show that a subset of them (24/163) neutralize all SARS-CoV-2 variants of concern (VOCs), including Omicron, potently. Therapeutic treatments with representative broadly neutralizing mAbs individually or antibody cocktails were highly protective against SARS-CoV-2 Beta infection in mice. Atomic structures of the Omicron S in complex with three types of all five VOC-reactive antibodies defined the binding and neutralizing determinants and revealed a key antibody escape site, G446S, that confers greater resistance to one major class of antibodies bound at the right shoulder of RBD through altering local conformation at the binding interface. Our results rationalize the use of 3-dose immunization regimens and suggest that the fundamental epitopes revealed by these broadly ultrapotent antibodies are a rational target for a universal sarbecovirus vaccine.One sentence summaryA sub-set of antibodies derived from memory B cells of volunteers vaccinated with 3 doses of an inactivated SARS-CoV-2 vaccine work individually as well as synergistically to keep variants, including Omicron, at bay.

As one of candidate structural materials for future fusion reactors, vanadium alloy has been widely studied in recent decades. In the present investigation, an attempt was made to determine the influence of high energy ions irradiation on the microstructures of V-4Cr-4Ti alloy which had been subjected to aging, cold deformation and heat-treatment. To achieve the aim, aging and cold reduction were carried out, followed by isothermal heat-treatment at 1100 °C for different time. Hardness measurement, optical and electron microscopies were employed to characterize microstructures of the samples. It was found that Ti-rich precipitates coherent to the matrix occur during aging. In the deformed samples, dislocation movement are inhibited by the precipitates, from which dislocation-precipitates interaction are formed. After 550 keV Fe10+ irradiation at 500 °C, a lot of voids, dislocation loops and fine precipitates occur in the alloy. The orientation of irradiation induced precipitates (Vanadium Carbide) is random. The sizes of voids are smaller in the annealed samples. The dislocation networks in the aged sample can remain partially after irradiation, due to pinning effect of precipitates formed during aging.

The goal of the present investigation is to explain the obviously different appearances of Ti-rich precipitates in vanadium alloy and in steels. To achieve the goal, the formation and evolution of the precipitates in the as-cast and the heat treated V–4Cr–4Ti samples were investigated using optical and electron microscopies. The precipitates were found to be rare in the as-cast samples, and a high density of the precipitates occur in the samples subjected to isothermal holding at 600–1300 °C. The precipitates preferentially distribute within the grains rather than at the grain boundaries. All of the precipitates are platelet-like, with NaCl structure, in three-dimensional space. The further observation using high-resolution electron microscopy (HREM) reveals that a high density of twins occurs in the growth front of the precipitates, whereas the middle of the precipitates is twin-free. Meanwhile, enrichment of titanium atoms was observed in the middle of the precipitates. These results indicate that the precipitates form by a displacive transformation, followed by a diffusional process to enrich titanium further and eliminate the twined structure.

The present work focuses the effect of the precipitate's shape on the hardness of V–4Cr–4Ti alloy. It is found that there are numerous lath-like Ti-rich precipitates occurring in the samples subjected to different heat treatment. The habit plane of these precipitates is the {200} plane of the matrix. The distribution density of the precipitates is closely related to heating temperatures and times. The hardness valley of the samples occurs at the heating temperatures corresponding to the high distribution density of precipitates. The abnormal hardening effect can be interpreted by a model, in term of which lath-like precipitates with high distribution density result in single gliding of dislocations and reduced work-hardening.

The V–4Cr–4Ti alloy which contains the pre-precipitates has been subjected to implantation of high energy ions at room temperature. It was found that the Ti-rich precipitates occur at grain boundaries while the far finer precipitates form within the grains. The ion implantation also results in variation of appearance of the pre-precipitates in the samples. These results indicate that diffusion in the samples is obviously enhanced by ion implantation-induced vacancies. The vacancies will disappear at the grain boundaries and the precipitates/matrix interfaces, which will transfer vanadium atoms prior out of the boundaries or the interfaces due to Kirkendall effect. In this way, the Ti-rich precipitates will form at the boundaries. Meanwhile, the pre-precipitates will change their shape.

Microstructures of casting samples of Fe–9%Cr steel and samples subjected to different heat treatments were investigated to determine their formation and evolution mechanism. The results show that there is no macroscopic segregation in the casting Fe–9%Cr steel. During cooling from solidification temperature to room temperature, δ-ferrite → austenite transformation is obviously influenced by cooling rate, while subsequent transformation of austenite does not obviously depend on the cooling rate. In the casting samples, a great number of precipitates distribute inside martensitic laths while there are almost no precipitates inside δ-ferrite. When the casting samples were reheated to and isothermally held at 800 °C, the original precipitates and the lath boundaries disappeared gradually. Meanwhile, new precipitates nucleate and grow at the prior lath boundaries.