Comprehensive structural analysis reveals broad-spectrum neutralizing antibodies against Omicron (preprint)

The pandemic of COVID-19 caused by SARS-CoV-2 continues to spread around the world. Mutant strains of SARS-CoV-2 are constantly emerging. At present, Omicron variants have become mainstream. In this work, we carried out a systematic and comprehensive analysis of the reported spike protein antibodies, counting the antibodies' epitopes and genotypes. We further comprehensively analyzed the impact of Omicron mutations on antibody epitopes and classified these antibodies according to their binding patterns. We found that the epitopes of one class of antibodies were significantly less affected by Omicron mutations than other classes. Binding and virus neutralization experiments show that such antibodies can effectively inhibit the immune escape of Omicron. Cryo-EM results show that this class of antibodies utilizes a conserved mechanism to neutralize SARS-CoV-2. Our results greatly help us deeply understand the impact of Omicron mutations. At the same time, it also provides guidance and insights for developing Omicron antibodies and vaccines.

2019冠状病毒病(COVID-19)诊疗浙江经验 Management of COVID-19: the Zhejiang experience

当前2019冠状病毒病（COVID-19）疫情仍处于胶着状态。浙江大学医学院附属第一医院是国家感染性疾病临床医学中心，浙江省COVID-19患者救治中心。疫情一线的专家集智攻关，以国家卫生健康委员会和国家中医药管理局发布的COVID-19诊治指南为依据，以抗病毒、抗休克、抗低氧血症、抗继发感染、维持水电解质和酸碱平衡、维持微生态平衡的“四抗二平衡”救治策略为核心，总结完善诊治方案，聚焦临床实践的一些具体问题，为COVID-19患者临床诊治提供借鉴。推荐以多学科协作诊治个性化治疗提高COVID-19患者救治质量。建议病原学检测、炎症指标监测和肺部影像学动态观察指导临床诊治。痰液的病毒核酸检测阳性率最高，约10%的急性期患者血液中检测到病毒核酸，50%的患者粪便中检测到病毒核酸，粪便中可分离出活病毒，须警惕粪便是否具有传染性；开展细胞因子等炎症指标监测有助于发现是否出现细胞因子风暴，判断是否需要人工肝血液净化治疗。通过以“四抗二平衡”为核心的综合治疗提高治愈率、降低病死率；早期抗病毒治疗能减少重症、危重症发生，前期使用阿比多尔联合洛匹那韦/利托那韦抗病毒显示出一定效果。休克和低氧血症多为细胞因子风暴所致，人工肝血液净化治疗能迅速清除炎症介质，阻断细胞因子风暴，对维持水电解质酸碱平衡也有很好的作用，可以提高危重型患者的疗效。重型病例疾病早期可适量、短程应用糖皮质激素。氧疗过程中，患者氧合指数小于200 mmHg时应及时转入重症医学科治疗；采用保守氧疗策略，不推荐常规进行无创通气；机械通气患者应严格执行集束化呼吸机相关性肺炎预防管理策略；氧合指数大于150 mmHg时，及早减、停镇静剂并撤机拔管。不推荐预防性使用抗菌药物，对于病程长，体温反复升高和血降钙素原水平升高的患者可酌情使用抗菌药物；要关注COVID-19患者继发真菌感染的诊治。COVID-19患者有肠道微生态紊乱，肠道乳酸杆菌、双歧杆菌等有益菌减少，推荐对所有患者进行营养和胃肠道功能评估，以营养支持和补充大剂量肠道微生态调节剂，纠正肠道微生态失衡，减少细菌移位和继发感染。COVID-19患者普遍存在焦虑和恐惧心理，应建立动态心理危机干预和处理。提倡中西医结合辨证施治；优化重型患者护理促进康复。严重急性呼吸综合征冠状病毒2（SARS-CoV-2）感染后病毒清除规律仍不明了，出院后仍须居家隔离2周，并定期随访。以上经验和建议在本中心实行，取得较好效果，但COVID-19是一种新的疾病，其诊治方案及策略仍有待进一步探索与完善。

Serum Unconjugated Bilirubin as a Predictor of Specific Cellular Immunity Response in Kidney Transplant Recipients after Administration of SARS-CoV-2 Inactivated Vaccine (preprint)

Purpose: The immunogenicity of SARS-CoV-2 vaccines is poor in kidney transplant recipients (KTRs). The factors related to poor immunogenicity to vaccination in KTRs are not well defined. Methods An observational study was conducted in KTRs and healthy individuals who had received two doses of SARS-CoV-2 inactivated vaccine. IgG antibodies against the receptor-binding domain found in the S1 subunit of the spike protein, and against nucleocapsid protein were measured using enzyme-linked immunosorbent assay. Receptor-binding domain (RBD)-angiotensin-converting enzyme 2 interaction-blocking antibodies were measured using commercial kits. T cell responses against the spike and nucleocapsid proteins were detected using enzyme-linked immunosorbent spot assay. Results No severe adverse effects were observed in KTRs after first or second dose of SARS-CoV-2 inactivated vaccine. IgG antibodies against the receptor- binding domain, and nucleocapsid protein were not effectively induced in a majority of KTRs after second dose of inactivated vaccine. Specific T cell immunity response was detectable in 32%-40% KTRs after second doses of inactivated vaccine. KTRs who developed specific T cell immunity were more likely to be female, and have lower levels of total bilirubin, unconjugated bilirubin, and blood tacrolimus concentration. Multivariate logistic regression analysis found that blood unconjugated bilirubin was significantly negatively associated with SARS-CoV-2 specific T cell immunity response in k KTRs. Conclusions Specific T cell immunity response could be induced in 32%-40% KTRs after two doses of inactivated vaccine. Blood unconjugated bilirubin was negatively associated with specific cellular immunity response in KTRs following vaccination.

PAGEANT: Personal Access to Genome and Analysis of Natural Traits (preprint)

GWASs have identified numerous genetic variants associated with a wide variety of diseases, yet despite the wide availability of genetic testing the insights that would enhance the interpretability of these results are not widely available to members of the public. As a proof of concept and demonstration of technological feasibility, we developed PAGEANT ( P ersonal A ccess to Ge nome & A nalysis of N atural T raits), usable through Graphical User Interface or command line-based version, aiming to serve as a protocol and prototype that guides the overarching design of genetic reporting tools. PAGEANT is structured across five core modules, summarized by five Qs: (1) Quality assurance of the genetic data; (2) Qualitative assessment of genetic characteristics; (3) Quantitative assessment of health risk susceptibility based on polygenic risk scores and population reference; (4) Query of third-party variant databases (e.g., ClinVAR and PharmGKB); and (5) Quick Response code of genetic variants of interest. Literature review was conducted to compare PAGEANT with academic and industry tools. For 2,504 genomes made publicly available through the 1,000 Genomes Project, we derived their genomic characteristics for a suite of qualitative and quantitative traits. One exemplary trait is susceptibility to COVID-19, based on the most up-to-date scientific findings reported.

Novel neutralization mechanism of a human antibody with pan-coronavirus reactivity (preprint)

The recurrent outbreak of coronaviruses and variants underscores the need for broadly reactive antivirals and vaccines. Here, a novel broad-spectrum human antibody named 76E1 was isolated from a COVID-19 convalescent patient and showed broad neutralization activity against multiple α- and β-coronaviruses, including the SARS-CoV-2 variants and also exhibited the binding breath to peptides containing the epitope from γ- and δ- coronaviruses. 76E1 cross-protects mice from SARS-CoV-2 and HCoV-OC43 infection in both prophylactic and treatment models. The epitope including the fusion peptide and S2’ cleavage site recognized by 76E1 was significantly conserved among α-, β-, γ- and δ- coronaviruses. We uncovered a novel mechanism of antibody neutralization that the epitope of 76E1 was proportionally less exposed in the prefusion trimeric structure of spike protein but could be unmasked by binding to the receptor ACE2. Once the epitope exposed, 76E1 inhibited S2’ cleavage, thus blocked the membrane fusion process. Our data demonstrate a key epitope targeted by broadly-neutralizing antibodies and will guide next-generation epitope-based pan-coronavirus vaccine design.

Broad ultra-potent neutralization of SARS-CoV-2 variants by monoclonal antibodies specific to the tip of RBD (preprint)

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) variants of concern (VOCs) continue to wreak havoc across the globe. Higher transmissibility and immunologic resistance of VOCs bring unprecedented challenges to epidemic extinguishment. Here we describe a monoclonal antibody, 2G1, that neutralizes all current VOCs and has surprising tolerance to mutations adjacent to or within its interaction epitope. Cryo-electron microscopy structure showed that 2G1 bound to the tip of receptor binding domain (RBD) of spike protein with small contact interface but strong hydrophobic effect, which resulted in nanomolar to sub-nanomolar affinities to spike proteins. The epitope of 2G1 on RBD partially overlaps with ACE2 interface, which gives 2G1 ability to block interaction between RBD and ACE2. The narrow binding epitope but high affinity bestow outstanding therapeutic efficacy upon 2G1 that neutralized VOCs with sub-nanomolar IC50 in vitro. In SARS-CoV-2 and Beta- and Delta-variant-challenged transgenic mice and rhesus macaque models, 2G1 protected animals from clinical illness and eliminated viral burden, without serious impact to animal safety. Mutagenesis experiments suggest that 2G1 could be potentially capable of dealing with emerging SARS-CoV-2 variants in future. This report characterized the therapeutic antibodies specific to the tip of spike against SARS-CoV-2 variants and highlights the potential clinical applications as well as for developing vaccine and cocktail therapy.

Screening and molecular modeling evaluation of food peptides to inhibit key targets of COVID-19 virus

Peptide drugs, especially food-derived peptides, have a variety of functional activities including antiviral and may also have a therapeutic effect on COVID-19. In this study, comparing with the reported drugs, 79 peptides were found to bind to the key targets of COVID-19 virus with higher non-covalent interaction, while among them, six peptides showed high non-covalent interactions with the three targets, which may inhibit the COVID-19 virus. In the simulation, peptides of nine to 10 amino acids with a hydrophilic amino acid and acidic amino acid in the middle and aromatic amino acids on the side showed higher binding to angiotensin-converting enzyme 2 (ACE2). Peptides of five to six amino acids with a basic amnio acid in the head, acidic amnio acid in the neck, hydrophobicity group in the middle, and basic amino acids in the tail showed higher binding to COVID-19 virus main protease (M^pro), while those with basic amino acids and acidic amino acids in the two sides and aromatic amino acids in the middle might have stronger interaction with COVID-19 virus RNA-dependent RNA polymerase (RdRp).

A Stepped Wedge Cluster Randomized Control Trial to Evaluate the Implementation and Effectiveness of Optimized Quality-Improvement Initiatives in Improving Quality of Care for Acute Cardiac Events in Response to the COVID-19 Outbreak (preprint)

Background: The National Chest Pain Center Accreditation Program (CHANGE) is the first hospital-based, multifaceted, nationwide quality improvement (QI) initiative, to monitor and improve quality of ST-segment elevation myocardial infarction (STEMI) care in China. The QI initiatives, as implementation strategies, include a bundle of evidence-based interventions adapted for implementation in China. During the pandemic of coronavirus disease 2019 (COVID-19), fear of infection with severe acute respiratory syndrome coronavirus 2, national lockdowns, and altered health care priorities have highlighted the program’s importance in improving STEMI care quality. This study aims to minimize the adverse impact of the COVID-19 pandemic on the quality of STEMI care, by developing interventions that optimize the QI initiatives, implementing and evaluating the optimized QI initiatives, and developing scale-up activities of the optimized QI initiatives in response to COVID-19 and other public health emergencies.Methods: A stepped wedge cluster randomized control trial will be conducted in three selected cities of China: Wuhan, Suzhou, and Shenzhen. Two districts have been randomly selected in each city, yielding a total of 24 registered hospitals. This study will conduct a rollout in these hospitals every 3 months. The 24 hospitals will be randomly assigned to four clusters, and each cluster will commence the intervention (optimized QI initiatives) at one of the four steps. We will conduct hospital-based assessments, questionnaire surveys among health care providers, community-based household surveys, and key informant interviews during the trial. All outcome measures will be organized using the RE-AIM (reach, effectiveness, adoption, implementation, maintenance) framework, including implementation outcomes, service outcomes (e.g., treatment time), and patient outcomes (e.g., in-hospital mortality and 1-year complication). The Consolidated Framework for Implementation Research framework will be used to identify factors that influence implementation of the optimized QI interventions.Discussion: The study findings could be translated into a systematic solution to implementing QI initiatives in response to COVID-19 and future potential major public health emergencies. Such actionable knowledge is critical for implementors of scale-up activities in low- and middle-income settings.Trial registration: This study was registered in the Chinese Clinical Trial Registry (ChiCTR 2100043319), registered 10 February 2021

ACE2-Targeting Monoclonal Antibody As A "Pan" Coronavirus Blocker In Vitro and In A Mouse Model (preprint)

Coronaviruses have caused three major outbreaks of infectious disease since the beginning of 21st century. Broad-spectrum strategies that can be utilized in both current and future coronavirus outbreaks and mutation-tolerant are sought after. Here we report a monoclonal antibody 3E8 targeting human angiotensin-converting enzyme 2 (ACE2) neutralized pseudo-typed coronaviruse SARS-CoV-2, SARS-CoV-2-D614G, SARS-CoV and HCoV-NL63, without affecting physiological activities of ACE2 or causing toxicity in mouse model. 3E8 also blocked live SARS-CoV-2 infection in vitro and in a mouse model of COVID-19. Cryo-EM studies revealed the binding site of 3E8 on ACE2 and identified Histone 34 of ACE2 as a critical site of anti-viral epitope. Overall, our work has provided a potential pan coronavirus management strategy and disclosed a pan anti-coronavirus epitope on human ACE2 for the first time.

Antibody-dependent enhancement (ADE) of SARS-CoV-2 infection in recovered COVID-19 patients: studies based on cellular and structural biology analysis (preprint)

Antibody-dependent enhancement (ADE) has been reported in several virus infections including dengue fever virus, severe acute respiratory syndrome (SARS) and Middle East respiratory syndrome (MERS) coronavirus infection. To study whether ADE is involved in COVID-19 infections, in vitro pseudotyped SARS-CoV-2 entry into Raji cells, K562 cells, and primary B cells mediated by plasma from recovered COVID-19 patients were employed as models. The enhancement of SARS-CoV-2 entry into cells was more commonly detected in plasma from severely-affected elderly patients with high titers of SARS-CoV-2 spike protein-specific antibodies. Cellular entry was mediated via the engagement of Fc{gamma}RII receptor through virus-cell membrane fusion, but not by endocytosis. Peptide array scanning analyses showed that antibodies which promote SARS-CoV-2 infection targeted the variable regions of the RBD domain. To further characterize the association between the spike-specific antibody and ADE, an RBD-specific monoclonal antibody (7F3) was isolated from a recovered patient, which potently inhibited SARS-Cov-2 infection of ACE-2 expressing cells and also mediated ADE in Raji cells. Site-directed mutagenesis the spike RBD domain reduced the neutralization activity of 7F3, but did not abolish its binding to the RBD domain. Structural analysis using cryo-electron microscopy (Cryo-EM) revealed that 7F3 binds to spike proteins at a shift-angled pattern with one up and two down RBDs, resulting in partial overlapping with the receptor binding motif (RBM), while a neutralizing monoclonal antibody that lacked ADE activity binds to spike proteins with three up RBDs, resulting in complete overlapping with RBM. Our results revealed that ADE mediated by SARS-CoV-2 spike-specific antibodies could result from binding to the receptor in slightly different pattern from antibodies mediating neutralizations. Studies on ADE using antibodies from recovered patients via cell biology and structural biology technology could be of use for developing novel therapeutic and preventive measures for control of COVID-19 infection.

Molecular characterization of SARS-CoV-2 from Bangladesh: Implications in genetic diversity, possible origin of the virus, and functional significance of the mutations (preprint)

In a try to understand the pathogenesis, evolution, and epidemiology of the SARS-CoV-2 virus, scientists from all over the world are tracking its genomic changes in real-time. Genomic studies can be helpful in understanding the disease dynamics. We have downloaded 324 complete and near-complete SARS-CoV-2 genomes submitted in the GISAID database from Bangladesh which were isolated between 30 March to 7 September 2020. We then compared these genomes with the Wuhan reference sequence and found 4160 mutation events including 2253 missense single nucleotide variations, 38 deletions, and 10 insertions. The C>T nucleotide change was most prevalent possibly due to selective mutation pressure to reduce CpG sites to evade CpG targeted host immune response. The most frequent mutation that occurred in 98% of the isolates was 3037C>T which is a synonymous change that almost always accompanied 3 other mutations that include 241C>T, 14408C>T (P323L in RdRp), and 23403A>G (D614G in spike protein). The P323L was reported to increase mutation rate and D614G is associated with increased viral replication and currently the most prevalent variant circulating all over the world. We identified multiple missense mutations in B-cell and T-cell predicted epitope regions and/or PCR target regions (including R203K and G204R that occurred in 86% of the isolates) that may impact immunogenicity and/or RT-PCR based diagnosis. Our analysis revealed 5 large deletion events in ORF7a and ORF8 gene products that may be associated with less severity of the disease and increased viral clearance. Our phylogeny analysis identified most of the isolates belonged to the Nextstrain clade 20B (86%) and GISAID clade GR (88%). Most of our isolates shared common ancestors either directly with European countries or jointly with middle eastern countries as well as Australia and India. Interestingly, the 19B clade (GISAID S clade) was unique to Chittagong which was originally prevalent in China. This reveals possible multiple introductions of the virus in Bangladesh via different routes. Hence more genome sequencing and analysis with related clinical data are needed to interpret the functional significance and better predict the disease dynamics that may be helpful for policymakers to control the COVID-19 pandemic in Bangladesh.

Structural basis for bivalent binding and inhibition of SARS-CoV-2 infection by human potent neutralizing antibodies (preprint)

Neutralizing monoclonal antibodies (nAbs) to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) represent promising candidates for clinical intervention against coronavirus virus diseases 2019 (COVID-19). We isolated a large number of nAbs from SARS-CoV-2 infected individuals capable of disrupting proper interaction between the receptor binding domain (RBD) of the viral spike (S) protein and the receptor angiotensin converting enzyme 2 (ACE2). In order to understand the mechanism of these nAbs on neutralizing SARS-CoV-2 virus infections, we have performed cryo-EM analysis and here report cryo-EM structures of the ten most potent nAbs in their native full-length IgG or Fab forms bound to the trimeric S protein of SARS-CoV-2. The bivalent binding of the full-length IgG is found to associate with more RBD in the "up" conformation than the monovalent binding of Fab, perhaps contributing to the enhanced neutralizing activity of IgG and triggering more shedding of the S1 subunit from the S protein. Comparison of large number of nAbs identified common and unique structural features associated with their potent neutralizing activities. This work provides structural basis for further understanding the mechanism of nAbs, especially through revealing the bivalent binding and their correlation with more potent neutralization and the shedding of S1 subunit.

Engineered Trimeric ACE2 Binds and Locks "Three-up" Spike Protein to Potently Inhibit SARS-CoVs and Mutants (preprint)

SARS-CoV-2 enters cells via ACE-2, which binds the spike protein with moderate affinity. Despite a constant background mutational rate, the virus must retain binding with ACE2 for infectivity, providing a conserved constraint for SARS-CoV-2 inhibitors. To prevent mutational escape of SARS-CoV-2 and to prepare for future related coronavirus outbreaks, we engineered a de novo trimeric ACE2 (T-ACE2) protein scaffold that binds the trimeric spike protein with extremely high affinity (KD < 1 pM), while retaining ACE2 native sequence. T-ACE2 potently inhibits all tested pseudotyped viruses including SARS-CoV-2, SARS-CoV, eight naturally occurring SARS-CoV-2 mutants, two SARSr-CoVs as well as authentic SARS-CoV-2. The cryo-EM structure reveals that T-ACE2 can induce the transit of spike protein to "three-up" RBD conformation upon binding. T-ACE2 thus represents a promising class of broadly neutralizing proteins against SARS-CoVs and mutants.

ECMO Therapy for Critically Ill Coronavirus Disease 2019 Patients in Wuhan, China: A Retrospective Multicenter Cohort Study (preprint)

Background The coronavirus disease 2019 (COVID-19) pandemic has led to surges in the demand for extracorporeal membrane oxygenation (ECMO) therapy. However, little in-depth evidence is known about the application of ECMO therapy in COVID-19 patients.Methods This retrospective multicenter cohort study included 88 patients who had been diagnosed with COVID-19 and received ECMO therapy at seven designated hospitals in Wuhan, China. The clinical characteristics, laboratory examinations, treatments, and outcomes were extracted from electronic medical records and compared between weaned and non-weaned ECMO patients. The patients were followed until June 30, 2020. Logistic regression analyses were performed to identify the risk factors associated with unsuccessful ECMO weaning. Propensity score matching was used to match patients who received veno-venous ECMO with those who received invasive mechanical ventilation (IMV)-only therapy. The primary endpoint, 120-day all-cause mortality after intensive care unit (ICU) admission during hospitalization, was compared using a mixed-effect Cox model.Results Of 88 patients who received ECMO therapy, 27 and 61 patients were and were not successfully weaned from ECMO, respectively. Additionally, 15, 15, and 65 patients were further weaned from IMV, discharged from hospital, or died during hospitalization, respectively. A lymphocyte count ≤ 0.5 × 109/L and D-dimer concentration > 4 × the upper limit of normal at ICU admission, a peak PaCO2 > 60 mmHg at 24 hours before ECMO initiation, and no tracheotomy performed during the ICU stay were independently associated with lower odds of ECMO weaning. In the propensity score-matched analysis, a mixed-effect Cox model detected a lower hazard ratio for 120-day all-cause mortality after ICU admission during hospitalization in the ECMO group, as compared with the IMV-only group.Conclusion Patients in Wuhan who received ECMO therapy had a relatively high mortality rate. This outcome may be largely attributable to resource-limited situations during the COVID-19 outbreak. In future, the presence of lymphocytopenia and higher D-dimer concentrations at ICU admission and hypercapnia at 24 hours before ECMO initiation could help to identify patients with a poor prognosis. Moreover, tracheotomy could facilitate weaning from ECMO. Despite the high mortality, ECMO was associated with improved outcomes relative to IMV-only therapy in critically ill COVID-19 patients.

AXL Promotes SARS-CoV-2 Infection of Pulmonary and Bronchial Epithelial Cells (preprint)

The current coronavirus disease 2019 (COVID-19) pandemic presents a global public health challenge. The viral pathogen responsible, Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), binds to a host receptor ACE2 through its spike (S) glycoprotein, which mediates membrane fusion and virus entry. Although the role of ACE2 as a receptor for SARS-CoV-2 is clear, studies have shown that ACE2 expression across different human tissues is extremely low, especially in pulmonary and bronchial cells. Thus, other host receptors and/or co-receptors that promote the entry of SARS-CoV-2 into cells of the respiratory system might exist. In this study, we have identified tyrosine-protein kinase receptor UFO (AXL), specifically interacts with SARS-CoV-2 S on the host cell membrane. When overexpressed in cells that do not highly express either AXL or ACE2, AXL promotes virus entry as efficiently as ACE2. Strikingly, deleting AXL, but not ACE2, significantly reduces infection of pulmonary cells by the SARS-CoV-2 virus pseudotype. Soluble human recombinant AXL, but not ACE2, blocks SARS-CoV-2 virus pseudotype infection in pulmonary cells. Taken together, our findings suggest AXL may play an important role in promoting SARS-CoV-2 infection of the human respiratory system and is a potential target in future clinical intervention strategies.

Application of high-flow nasal cannula in hypoxemic patients with COVID-19: a retrospective cohort study (preprint)

Background: High-flow nasal cannula (HFNC) oxygen therapy provides effective respiratory support in patients with hypoxemic respiratory failure. However, the efficacy of HFNC for patients with COVID-19 has not been established. This study was performed to assess the efficacy of HFNC for patients with COVID-19 and describe early predictors of HFNC treatment success in order to develop a prediction tool that accurately identifies the need for invasive mechanical ventilation (IMV). Methods: We retrospectively reviewed the records of patients with COVID-19 who underwent HFNC in 2 hospitals in Wuhan between 1 January and 1 March 2020. Overall survival, the success rate of HFNC treatment and respiratory variables to predict the outcome of HFNC treatment were evaluated.Results: A total of 105 patients were analyzed. Of these, 65 patients (61.9%) showed improved oxygenation and were successfully withdrawn from HFNC. The oxygenation index (PaO2/FiO2), Oxygen saturation index (SpO2/FiO2) and respiratory rate-oxygenation index (ROX index: SpO2/FiO2*RR) at 6h, 12h and 24h of HFNC initiation were closely related to the prognosis. The best predictor was the ROX index at 24h after initiating HFNC (area under the receiver operating characteristic curve, 0.874). In the multivariate logistic regression analysis, young age, gender of female, and lower SOFA score all have predictive value, while a ROX index greater than 6.10 at 24 h after initiation was significantly associated with HFNC success (OR, 104.212; 95% CI, 11.399-952.757; p＜0.001).Conclusions: Our study indicated that HFNC was an effective way of respiratory support in the treatment of severe COVID-19. The ROX index greater than 6.10 at 24 h after initiating HFNC was a good predictor of successful HFNC treatment.

A potent neutralizing human antibody reveals the N-terminal domain of the Spike protein of SARS-CoV-2 as a site of vulnerability (preprint)

The pandemic of coronavirus disease 2019 (COVID-19) caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) presents a global public health threat. Most research on therapeutics against SARS-CoV-2 focused on the receptor binding domain (RBD) of the Spike (S) protein, whereas the vulnerable epitopes and functional mechanism of non-RBD regions are poorly understood. Here we isolated and characterized monoclonal antibodies (mAbs) derived from convalescent COVID-19 patients. An mAb targeting the N-terminal domain (NTD) of the SARS-CoV-2 S protein, named 4A8, exhibits high neutralization potency against both authentic and pseudotyped SARS-CoV-2, although it does not block the interaction between angiotensin-converting enzyme 2 (ACE2) receptor and S protein. The cryo-EM structure of the SARS-CoV-2 S protein in complex with 4A8 has been determined to an overall resolution of 3.1 Angstrom and local resolution of 3.4 Angstrom for the 4A8-NTD interface, revealing detailed interactions between the NTD and 4A8. Our functional and structural characterizations discover a new vulnerable epitope of the S protein and identify promising neutralizing mAbs as potential clinical therapy for COVID-19.

Deep Learning-based Detection for COVID-19 from Chest CT using Weak Label (preprint)

Accurate and rapid diagnosis of COVID-19 suspected cases plays a crucial role in timely quarantine and medical treatment. Developing a deep learning-based model for automatic COVID-19 detection on chest CT is helpful to counter the outbreak of SARS-CoV-2. A weakly-supervised deep learning-based software system was developed using 3D CT volumes to detect COVID-19. For each patient, the lung region was segmented using a pre-trained UNet; then the segmented 3D lung region was fed into a 3D deep neural network to predict the probability of COVID-19 infectious. 499 CT volumes collected from Dec. 13, 2019, to Jan. 23, 2020, were used for training and 131 CT volumes collected from Jan 24, 2020, to Feb 6, 2020, were used for testing. The deep learning algorithm obtained 0.959 ROC AUC and 0.976 PR AUC. There was an operating point with 0.907 sensitivity and 0.911 specificity in the ROC curve. When using a probability threshold of 0.5 to classify COVID-positive and COVID-negative, the algorithm obtained an accuracy of 0.901, a positive predictive value of 0.840 and a very high negative predictive value of 0.982. The algorithm took only 1.93 seconds to process a single patient's CT volume using a dedicated GPU. Our weakly-supervised deep learning model can accurately predict the COVID-19 infectious probability in chest CT volumes without the need for annotating the lesions for training. The easily-trained and high-performance deep learning algorithm provides a fast way to identify COVID-19 patients, which is beneficial to control the outbreak of SARS-CoV-2. The developed deep learning software is available at \url{https://github.com/sydney0zq/covid-19-detection}.

Structural basis for the recognition of the 2019-nCoV by human ACE2 (preprint)

Angiotensin-converting enzyme 2 (ACE2) has been suggested to be the cellular receptor for the new coronavirus (2019-nCoV) that is causing the coronavirus disease 2019 (COVID-19). Like other coronaviruses such as the SARS-CoV, the 2019-nCoV uses the receptor binding domain (RBD) of the surface spike glycoprotein (S protein) to engage ACE2. We most recently determined the structure of the full-length human ACE2 in complex with a neutral amino acid transporter B0AT1. Here we report the cryo-EM structure of the full-length human ACE2 bound to the RBD of the 2019-nCoV at an overall resolution of 2.9 [A] in the presence of B0AT1. The local resolution at the ACE2-RBD interface is 3.5 [A], allowing analysis of the detailed interactions between the RBD and the receptor. Similar to that for the SARS-CoV, the RBD of the 2019-nCoV is recognized by the extracellular peptidase domain (PD) of ACE2 mainly through polar residues. Pairwise comparison reveals a number of variations that may determine the different affinities between ACE2 and the RBDs from these two related viruses.