Current research on injury to the distal tibiofibular syndesmosis and prospects of its treatment / 中华创伤骨科杂志

Among ankle injuries, the injury to the distal tibiofibular syndesmosis is common and likely neglected. The stability of the distal tibiofibular syndesmosis is related to the depth of the fibular notch. In imaging diagnosis, X-ray examination cannot be used for a definite diagnosis of the injury to the distal tibiofibular syndesmosis. For diagnosis of the distal tibiofibular separation>3 mm, CT scan can be accurate but is not sensitive enough for a separation<1 mm while MRI is more sensitive in diagnosis of the injury. Arthroscopy has gradually been used as the "gold standard" in diagnosis of the injury to the distal tibiofibular syndesmosis due to its advantage of direct vision. The distal tibiofibular separation occurs in the injuries of pronation external rotation Ⅳ°, supination external rotation Ⅲ° and Ⅳ°, and pronation abduction Ⅱ° and Ⅲ° by the Lange-Hansen classification. Most patients with simple stable injury to the distal tibiofibular syndesmosis may have a good prognosis after nonoperative treatment. Surgical anatomic reduction and maintenance of stability of the distal tibiofibular syndesmosis are the basic management principles for unstable distal tibiofibular syndesmosis or the injury to the distal tibiofibular syndesmosis combined with ankle fracture. Screw fixation is the most commonly used in the surgical treatment of the injury. Elastic fixation has the advantages of maintaining the biological characteristics of the distal tibiofibular syndesmosis fretting joint, better reduction fault tolerance, and lower rates of complications and long-term reduction loss. The angle of nail placement is the key to maintaining good reduction of the distal tibiofibular syndesmosis, but there has been little description of the specific methods to ensure the theoretical angle of nail placement in practice. This article also reviews the prospects of the future treatment of the injury to the distal tibiofibular syndesmosis.

Application of targeted capture high depth sequencing and transcriptome sequencing in childhood B-cell acute lymphoblastic leukemia / 白血病·淋巴瘤

Objective:To investigate the differences among targeted capture high depth sequencing (Panel-seq), transcriptome sequencing (RNA-seq) and traditional detection methods in cytogenetic and molecular genetic typing of childhood B-cell acute lymphoblastic leukemia (B-ALL) and their significances.Methods:The clinical data of 152 newly diagnosed childhood B-ALL cases in Guangzhou Women and Children's Medical Center from September 2020 to December 2021 were retrospectively analyzed. Along with traditional cytogenetic and molecular detection methods including karyotyping, fluorescence in situ hybridization (FISH) and 43 kinds of fusion gene quantitative screening for traditional cells and molecular genetic detection, both Panel-seq and RNA-seq were also performed. Panel-seq covered more than 600 genes with common mutations in hematological tumors, from which fusion genes and gene mutations were both analyzed. RNA-seq was used to analyze fusion genes, gene mutations, gene expression, and copy number variation at the chromosome level. High hyperdiploid karyotype was estimated by using gene expression profile clustering and copy number variations. The cytogenetic typing results of all detection methods were also analyzed.Results:Among 152 patients, 93 cases were males and 59 cases were females, with the median age of 4.0 years (0.8-13.0 years). The median blast cell ratio was 0.855 (0.215-0.965). The traditional detection methods could identify 4 cases (2.6%) with BCR-ABL1, 2 cases (1.3%) with CRLF2 gene-related fusion, 27 cases (17.8%) with ETV6-RUNX1, 1 case (0.7%) with iAMP21, 5 cases (3.3%) with MLL rearrangement, 8 cases (5.3%) with TCF3-PBX1 and 22 cases (14.5%) with high hyperdiploid karyotype. Panel-seq could identify 4 cases (2.6%) with BCR-ABL1, 2 cases (1.3%) with CRLF2 gene-related fusions, 27 cases (17.8%) with ETV6-RUNX1, 3 cases (2.0%) with MEF2D gene-related fusions, 1 case (0.7%) with MEIS1-FOXO1, 5 cases (3.3%) with MLL rearrangement, 5 cases (3.3%) with PAX5 gene-related fusions, 8 cases (5.3%) with TCF3-PBX1 fusions, 4 cases (2.6%) with ZNF384 gene-related fusions, and 2 cases (1.3%) with IKZF1 N159Y mutations. Among 152 patients, 1 case with MLL rearrangement didn't receive RNA-seq detection because of sample quality; in other 151 B-ALL cases, 1 case (0.7%) with ACIN1-NUTM1, 4 cases (2.6%) with BCR-ABL1, 3 cases (2.0%) with CRLF2 gene-related fusions, 8 cases (5.3%) with DUX4 gene-related fusions, 27 cases (17.9%) with ETV6-RUNX1, 3 cases (2.0%) with MEF2D gene-related fusions, 1 case (0.7%) with MEIS1-FOXO1, 4 cases (2.6%) with MLL rearrangement, 5 cases (3.3%) with PAX5 gene-related fusions, 1 case (0.7%) with ZMIZ1-ABL1, 8 cases (5.3%) with TCF3-PBX1,4 cases (2.6%) with ZNF384 gene-related fusions, 61 cases (40.4%) with hyperdiploid karyotypes, and 2 cases (1.3%) with IKZF1 N159Y mutations were detected; RNA-seq had obvious advantage in detecting fusion gene and hyperdiploid karyotype. The cytogenetic and molecular genetic typing rates of traditional method, Panel-seq and RNA-seq were 45.4% (69/152), 40.1% (61/152) and 87.4% (132/151), respectively. The combination of the three could identify 89.5% (136/152) of childhood B-ALL patients.Conclusions:The combination of Panel-seq and RNA-seq can increase the detection rate of genetic abnormality in childhood B-ALL, which provides a more accurate molecular genetic classification for B-ALL and the basis for treatment guideline and prognosis judgement.

Neutralization of Omicron BA.4/BA.5 and BA.2.75 by Booster Vaccination or BA.2 Breakthrough Infection Sera

Many new Omicron sub-lineages have been reported to evade neutralizing antibody response, including BA.2, BA.2.12.1, BA.4 and BA.5. Most recently, another emerging sub-lineage BA.2.75 has been reported in multiple countries. In this study, we constructed a comprehensive panel of pseudoviruses (PsVs), including wild-type, Delta, BA.1, BA.1.1, BA.2, BA.3, BA.2.3.1, BA.2.10.1, BA.2.12.1, BA.2.13, BA.2.75 and BA.4/BA.5, with accumulate coverage reached 91% according to the proportion of sequences deposited in GISAID database since Jan 1st, 2022. We collected serum samples from healthy adults at day14 post homologous booster with BBIBP-CorV, or heterologous booster with ZF2001, primed with two doses of BBIBP-CorV, or from convalescents immunized with three-dose inactivated vaccines prior to infection with Omicron BA.2, and tested their neutralization activity on this panel of PsVs. Our results demonstrated that all Omicron sub-lineages showed substantial evasion of neutralizing antibodies induced by vaccination and infection, although BA.2.75 accumulated the largest number of mutations in its spike, BA.4 and BA.5 showed the strongest serum escape. However, BA.2 breakthrough infection could remarkably elevated neutralization titers against all different variants, especially titers against BA.2 and its derivative sub-lineages.

Antibody Resistance of SARS-CoV-2 Omicron BA.1, BA.1.1, BA.2 and BA.3 Sub-lineages

The SARS-CoV-2 Omicron variant has been partitioned into four sub-lineages designated BA.1, BA.1.1, BA.2 and BA.3, with BA.2 becoming dominant worldwide recently by outcompeting BA.1 and BA.1.1. We and others have reported the striking antibody evasion of BA.1 and BA.2, but side-by-side comparison of susceptibility of all the major Omicron sub-lineages to vaccine-elicited or monoclonal antibody (mAb)-mediated neutralization are urgently needed. Using VSV-based pseudovirus, we found that sera from individuals vaccinated by two doses of inactivated whole-virion vaccines (BBIBP-CorV) showed very weak to no neutralization activity, while a homologous inactivated vaccine booster or a heterologous booster with protein subunit vaccine (ZF2001) markedly improved the neutralization titers against all Omicron variants. The comparison between sub-lineages indicated that BA.1.1, BA.2 and BA.3 had comparable or even greater antibody resistance than BA.1. We further evaluated the neutralization profile of a panel of 20 mAbs, including 10 already authorized or approved, against these Omicron sub-lineages as well as viruses with different Omicron spike single or combined mutations. Most mAbs lost their neutralizing activity completely or substantially, while some demonstrated distinct neutralization patterns among Omicron sub-lineages, reflecting their antigenic difference. Taken together, our results suggest all four Omicron sub-lineages threaten the efficacies of current vaccines and antibody therapeutics, highlighting the importance of vaccine boosters to combat the emerging SARS-CoV-2 variants.

An operative position of foot stepping and knee bending in toe replantation for avulsed and fractured great toe / 中华显微外科杂志

Objective:To summarise the advantages and disadvantages of applying the method of retrograde replantation with an operative position of foot stepping and knee bending for replantation of rotational avulsed and fractured great toes.Methods:From January 2016 to June 2021, 11 rotational avulsed and fractured great toes were replanted with the method of retrograde replantation in an operative position of foot stepping and knee bending. Of the 11 patients, 10 were males and 1 was female, aged 18 to 50 years old with an average of 32 years old. Causes of injury: 5 of driving belt, 4 of machinery crush and 2 of car accident. Injury sites: 4 on left great toes and 7 on right great toes. All of the injuries were with fracture and exposure of proximal tendons of flexor and extensor. Seven patients had the follow-up reviews by outpatient clinic visiting, 2 over mobile phone and 2 via WeChat.Results:After surgery, 9 great toes completely survived and 2 great toes had necrosis. The survival rate of toe replantation was 81.8%(9/11). The operation time was 2 to 3 hours, with an average of 2.5 hours. Postoperative X-ray film showed that 8 to 12 weeks after the operation, the fracture and joint fusion were healed at first stage in the survived toes. All patients were entered in follow-up for 3 to 18 months with 10.5 months in average. The survived great toes were plump and the toenail grown well. At the final follow-up, the static TPD at the toes was 8-12 mm, with an average of 10 mm. There was no effect shown on either walking or running.Conclusion:The retrograde replantation method with an operative position of foot stepping and knee bending for great toe replantation has the characteristics of a good field of view and convenient in operation under microscope, a short operation time, and a high survival rate of replantation.

Predictive value of collateral scores in acute basilar artery occlusion patients treated with endovascular therapy / 国际脑血管病杂志

The mortality and disability of patients with acute basilar artery occlusion (ABAO) are extremely high without endovascular therapy. However, there is a lack of clear criteria for screening people who benefit from endovascular therapy for patients with ABAO. A large number of studies have shown that the collateral circulation status is crucial to judge the clinical outcome of patients with ABAO after endovascular therapy. The posterior circulation collateral scoring systems have been proposed according to different imaging methods. This article reviews the posterior circulation collateral scores and thier predictive value in ABAO patients treated with endovascular therapy.

Clinical significance of excessive inlet view in fluoroscopy-assisted placement of sacroiliac screws / 中华创伤骨科杂志

Objective:To investigate the clinical significance of excessive inlet view in fluoroscopy-assisted placement of sacroiliac screws.Methods:Included for this prospective study were 47 patients with unstable pelvic fracture who had been admitted to Department of Orthopaedic Trauma, Xi'an Honghui Hospital between January 2020 and January 2021. There were 30 males and 17 females, with a mean age of 39.4 years (from 25 to 66 years). By the Tile classification, 21 fractures were type B and 26 ones type C. The inlet view and the angle of excessive inlet view were measured before operation. The intraoperative placement of sacroiliac screws was assisted by C-arm fluoroscopy navigation in the excessive inlet view. The positions of sacroiliac screws were verified by CT or O-arm fluoroscopy after operation. The screw placement time, fracture reduction quality, fracture healing time, and pelvic function at the last follow-up were recorded.Results:A total of 67 screws were implanted in the 47 patients, including 56 sacroiliac screws. The insertion time for each screw averaged 19.9 min (from 9 to 31 min); the angle of excessive inlet view averaged 17.38° (from 12.1° to 24.8°). Verification by O-arm fluoroscopy or CT revealed that all sacroiliac screws were located in the sacral canal without dislocation or breaking through the cortical bone. By the postoperative Matta scoring, the reduction was excellent in 22 cases, good in 17, acceptable in 6, and poor in 2, giving an excellent to good rate of 83.0%(39/47). The average follow-up time for the 47 patients was 9.5 months (from 5 to 15 months); fracture healing time averaged 10.5 weeks (from 7 to 16 weeks). By the Mejeed scoring at the last follow-up, the pelvic function was excellent in 26 cases, good in 15 and acceptable in 6, giving an excellent to good rate of 87.2% (41/47).Conclusions:Fluoroscopy in the excessive inlet view is a simple and easy intraoperative technique. It can improve accuracy and safety of sacroiliac screw placement because it allows clear identification of the posterior border of the sacrum and effectively avoids iatrogenic injury to the sacral nerve caused by screws breaking through the bone cortex.

Epidemiological characteristics of geriatric acetabular fracture in western China during 2015-2020 / 中华创伤杂志

Objective:To analyze the epidemiological characteristics of geriatric acetabular fractures in western China.Methods:A retrospective case series study was made on data of geriatric patients with acetabular fracture hospitalized in 4 grade A hospitals in western China from 2015 to 2020. The investigation content included gender, age, incidence rate, injury mechanism, combined injuries, comorbidities, fracture types and treatment plans.Results:A total of 299 geriatric patients with acetabular fractures were included, including 203 males and 96 females, aged 60-97 years [(68.6±7.6)years]. The mean age of the patients was increased from 67.5 years to 71.1 years. The incidence rate was increased from 36 cases per year to 64 cases per year. The injury mechanism was mainly traffic accidents (42.47%), followed by falls (30.44%). Thoracic injury was the most common type of combined injuries (39.81%). Hypertension was the main comorbidity (28.76%). The most common fracture type was anterior column posterior hemitransverse fracture (31.32%). Of 299 patients, 210 received surgical treatment, with the surgery rate of 70.23%.Conclusions:Geriatric acetabular fracture is characterized by gradually increased age and incidence rate, traffic accidents as the main cause of injury, thoracic injury as the main combined injury, hypertension as the main comorbidity, anterior column posterior hemitransverse fracture as the main fracture type and surgery as the main treatment option.

Effect of emergency heart failure units on readmission and mortality within 6 months after discharge in patients with acute heart failure / 中华急诊医学杂志

Objective:At present, emergency acute heart failure unit has been gradually carried out in China. This study is to analyze the impact of acute heart failure unit on the mortality and readmission rate of acute heart failure (AHF) within 6 months after discharge.Methods:Patients with AHF admitted to Emergency Department and Department of Cardiology, Peking University People's Hospital between December 2019 and December 2020, were prospectively collected. Patients with complicated malignant tumor, stage 4-5 chronic kidney disease, automatic discharge, and incomplete medical history were excluded. The baseline data, past medical history, admission condition, and auxiliary examination were collected. After discharge, the information of oral drugs, hospital readmission and death were collected through outpatient medical records in clinical data center or telephone consultation. Patients were divided into the emergency acute heart failure unit treatment group (emergency AHFU group), emergency routine treatment group (outside AHFU group) and cardiology treatment group according to the different treatment locations. SPSS 25.0 software was used for comparison between groups, and a P<0.05 was considered as statistically significant. ResuIts:A total of 238 patients with AHF were enrolled, 28 patients died in hospital, and 210 patients were followed up. Four cases were excluded from malignant tumor during follow-up, and 6 cases were lost to follow-up. There were 40 cases in the emergency AHFU group, 67 cases in the outside AHFU group, and 93 cases in the cardiology treatment group. According to the prognosis, the patients were divided into the poor prognosis group ( n=83) and good prognosis group ( n=145). The age, sex, vital signs and cardiac function of patients in the emergency AHFU group were basically the same as those in the outside AHFU group at admission, and the proportion of patients in the emergency AHFU group using non-invasive positive pressure ventilation was higher (52.5% vs. 32.8%, P<0.05). The utilization rate of angiotensin converting enzyme inhibitors/angiotensin receptor blockers/angiotensin receptor enkephalinase inhibitors, β-blockers, diuretics and other oral drugs was higher in the emergency AHFU group after discharge, and patients also had more regular follow-up (95% vs. 79.1%, P<0.05). The 6-month readmission rate (15.0% vs. 40.3%, P<0.05) and the 6-month readmission and mortality composite results of patients in the emergency AHFU group (17.5% vs. 43.3%, P<0.05) were significantly lower than those in the outside AHFU group. COX regression analysis showed that the readmission rate of patients in the emergency AHFU group was lower than that in the outside AHFU group ( OR=2.882, 95% CI:1.267~6.611, P=0.12). Compared with the cardiology treatment group, the AHFU group had higher systolic blood pressure, faster heart rate, NT-probNP level, higher proportion of NYHA grade Ⅳ and Killip grade Ⅲ cardiac function (all P<0.05). The proportion of non-invasive mechanical ventilation in the AHFU group was significantly higher than that in the cardiology treatment group (52.5% vs. 30.1%, P<0.05). After discharge, there were no significant differences between angiotensin converting enzyme inhibitor/angiotensin receptor blocker/angiotensin receptor enkephalinase inhibitors and β-blockers. There were also no significant differences in readmission and mortality rate 6 months after discharge. Binary logistics regression analysis found that the independent risk factors of AHF were routine emergency treatment, age, female sex, coronary heart disease, and BUN peak. Conclusions:The emergency acute heart failure unit is an independent protective factor for acute heart failure and reduced readmission rates within 6 months and readmission and mortality composite outcomes. Older age, female sex, coronary heart disease and elevated BUN peak are independent risk factors affecting the prognosis of AHF, which should be identified and preventive measures should be taken early.

TiRobot combined with O-arm assisted closed reduction and percutaneous screw fixation in unstable pelvic fracture surgery / 中华骨科杂志

Objective:To investigate the role of TiRobot combined with O-arm assisted closed reduction and percutaneous screw fixation in unstable pelvic fracture surgery.Methods:Twelve patients with unstable pelvic fractures, 7 males and 5 females, aged 39.41±12.56 years (range 25-60 years), admitted from January 2020 to January 2021, were retrospectively analyzed. The duration between injury and surgery was 9.67±5.81 d (range 4-24 d). The following are the causes of injury, namely traffic injury in 6 cases, fall from height injury in 4 cases, crush injury in 2 cases. Tile type of pelvic fractures were 3 cases of type B (2 cases of type B2, 1 case of type B3), 9 cases of type C (4 cases of type C1, 3 cases of type C2, 2 cases of type C3). Sacral fractures with Denis division were 5 cases of zone I, 7 cases of zone II. Seven patients were repositioned by intraoperative traction on the injured side of the limb and maintained by fixation with a Starr frame. Two cases were repositioned by intraoperative longitudinal bone traction on each lower limb for fracture displacement. The other 3 B-type fractures were repositioned by inserting Schanz nails into the anterior inferior iliac spine bilaterally. Then, the fractures were maintained with external pelvic fixators. The fractures were assessed by O-arm fluoroscopy. Hollow screws were placed with the aid of orthopedic robotic guidance, and the screw positions were verified by O-arm fluoroscopy again after the nail placement. The duration of each screw placement and operation were recorded. The quality of fracture repositioning, hip function and postoperative complications were observed at the follow-up.Results:All patients were followed up for 8.17±1.99 months (range, 6-12 months). There were 27 screws inserted in 12 patients, with a single screw insertion duration of 19.9±1.8 min (range, 9-31 min). In all patients, one O-arm fluoroscopy was performed in each row after closed reduction and after completion of nail placement. The operative duration was 257.78±80.63 min (range, 160-450 min). The O-arm fluoroscopy after nail placement verified that 23 screws were placed in a satisfactory position at one time, with satisfactory rate of 85% (23/27) for the first nail placement. Two patients with preoperative grade II sacral plexus nerve injury recovered to grade I in one case and grade II in one case. However, the numbness was reduced after operation. No further aggravation of nerve injury occurred after surgery. The quality of fracture repositioning was evaluated according to the Matta score, including excellent in 9 cases, good in 2 cases, and acceptable in 1 case, with an excellent rate of 92% (11/12). At the last follow-up, the Majeed pelvic fracture quantitative assessment system scored 85.75±5.82 (range, 74-96). There were 8 cases in excellent and 4 cases in good. Twelve patients had one-stage wound healing. No complications, such as incision infection, nerve injury, loosening and breaking of the internal fixation occurred during the follow-up.Conclusion:TiRobot combined with O-arm assisted closed reduction and percutaneous screw fixation for unstable pelvic fractures has some advantages, including safety, precision, convenient nail placement, and less fluoroscopic radiation.

Treatment of Schatzker type Ⅳ tibial plateau fracture involving the postero-lateral condyle with a medial support plate and a row of screws / 中华创伤骨科杂志

Objective:To investigate the clinical efficacy of a medial support plate and a row of screws in the treatment of Schatzker type Ⅳ tibial plateau fracture involving the postero-lateral condyle.Methods:A retrospective analysis was performed of the data of 26 patients who had been admitted to Department of Orthopedic Trauma, Honghui Hospital Affiliated to Xi'an Jiaotong University for Schatzker type Ⅳ tibial plateau fracture involving the postero-lateral condyle from December 2015 to December 2020. There were 17 males and 9 females, aged from 19 to 51 years (average, 36.1 years). All their fracture lines involved the postero-lateral condyle and all fractures were fixated with a medial support plate and a row of screws via one medial and one lateral incisions. Recorded were the operation time, hospital stay, blood loss, incision length, fracture healing, complications, quality of knee joint reduction and knee joint function at the last follow-up.Results:The length of hospital stay ranged from 8 to 16 days, averaging 10.4 days. The 26 patients were followed up for 8 to 18 months, with an average of 14.3 months. All the fractures got united after 11 to 17 weeks (average, 13.7 weeks). During the follow-up, no reduction loss, internal fixation failure or surgical complications were observed. Rasmussen radiographic scores at the last follow-up ranged from 11 to 18 points, averaging 16.1 points. The range of motion of the knee joint ranged from 0° to 140°, averaging 120.8°. The Rasmussen scores of the knee function ranged from 14 to 28 points, averaging 24.4 points.Conclusion:In the treatment of Schatzker type Ⅳ tibial plateau fracture involving the postero-lateral condyle, the use of a medial support plate and a row of screws can achieve satisfactory clinical results.

Homologous or Heterologous Booster of Inactivated Vaccine Reduces SARS-CoV-2 Omicron Variant Escape from Neutralizing Antibodies

The massive and rapid transmission of SARS-CoV-2 has led to the emergence of several viral variants of concern (VOCs), with the most recent one, B.1.1.529 (Omicron), which accumulated a large number of spike mutations, raising the specter that this newly identified variant may escape from the currently available vaccines and therapeutic antibodies. Using VSV-based pseudovirus, we found that Omicron variant is markedly resistant to neutralization of sera form convalescents or individuals vaccinated by two doses of inactivated whole-virion vaccines (BBIBP-CorV). However, a homologous inactivated vaccine booster or a heterologous booster with protein subunit vaccine (ZF2001) significantly increased neutralization titers to both WT and Omicron variant. Moreover, at day 14 post the third dose, neutralizing antibody titer reduction for Omicron was less than that for convalescents or individuals who had only two doses of the vaccine, indicating that a homologous or heterologous booster can reduce the Omicron escape from neutralizing. In addition, we tested a panel of 17 SARS-CoV-2 monoclonal antibodies (mAbs). Omicron resists 7 of 8 authorized/approved mAbs, as well as most of the other mAbs targeting distinct epitopes on RBD and NTD. Taken together, our results suggest the urgency to push forward the booster vaccination to combat the emerging SARS-CoV-2 variants.

A monoclonal antibody that neutralizes SARS-CoV-2 variants, SARS-CoV, and other sarbecoviruses

The repeated emergence of highly pathogenic human coronaviruses as well as their evolving variants highlight the need to develop potent and broad-spectrum antiviral therapeutics and vaccines. By screening monoclonal antibodies (mAbs) isolated from COVID-19-convalescent patients, we found one mAb, 2-36, with cross-neutralizing activity against SARS-CoV. We solved the cryo-EM structure of 2-36 in complex with SARS-CoV-2 or SARS-CoV spike, revealing a highly conserved epitope in the receptor-binding domain (RBD). Antibody 2-36 neutralized not only all current circulating SARS-CoV-2 variants and SARS-COV, but also a panel of bat and pangolin sarbecoviruses that can use human angiotensin-converting enzyme 2 (ACE2) as a receptor. We selected 2-36-escape viruses in vitro and confirmed that K378T in SARS-CoV-2 RBD led to viral resistance. Taken together, 2-36 represents a strategic reserve drug candidate for the prevention and treatment of possible diseases caused by pre-emergent SARS-related coronaviruses. Its epitope defines a promising target for the development of a pan-sarbecovirus vaccine.

Neutralizing antibody 5-7 defines a distinct site of vulnerability in SARS-CoV-2 spike N-terminal domain

Antibodies that potently neutralize SARS-CoV-2 target mainly the receptor-binding domain or the N-terminal domain (NTD). Over a dozen potently neutralizing NTD-directed antibodies have been studied structurally, and all target a single antigenic supersite in NTD (site 1). Here we report the 3.7 [A] resolution cryo-EM structure of a potent NTD-directed neutralizing antibody 5-7, which recognizes a site distinct from other potently neutralizing antibodies, inserting a binding loop into an exposed hydrophobic pocket between the two sheets of the NTD {beta}-sandwich. Interestingly, this pocket has been previously identified as the binding site for hydrophobic molecules including heme metabolites, but we observe their presence to not substantially impede 5-7 recognition. Mirroring its distinctive binding, antibody 5-7 retains a distinctive neutralization potency with variants of concern (VOC). Overall, we reveal a hydrophobic pocket in NTD proposed for immune evasion can actually be used by the immune system for recognition. HighlightsO_LICryo-EM structure of neutralizing antibody 5-7 in complex with SARS CoV-2 spike C_LIO_LI5-7 recognizes NTD outside of the previously identified antigenic supersite C_LIO_LI5-7 binds to a site known to accommodate numerous hydrophobic ligands C_LIO_LIStructural basis of 5-7 neutralization tolerance to some variants of concern C_LI

Increased Resistance of SARS-CoV-2 Variant P.1 to Antibody Neutralization

The relative resistance of SARS-CoV-2 variants B.1.1.7 and B.1.351 to antibody neutralization has been described recently. We now report that another emergent variant from Brazil, P.1, is not only refractory to multiple neutralizing monoclonal antibodies, but also more resistant to neutralization by convalescent plasma (3.4 fold) and vaccinee sera (3.8-4.8 fold). The cryo-electron microscopy structure of a soluble prefusion-stabilized spike reveals the P.1 trimer to adopt exclusively a conformation in which one of the receptor-binding domains is in the "up" position, with the functional impact of mutations appearing to arise from local changes instead of global conformational alterations. The P.1 variant threatens current antibody therapies but less so the protective efficacy of our vaccines.

Structural Basis for Accommodation of Emerging B.1.351 and B.1.1.7 Variants by Two Potent SARS-CoV-2 Neutralizing Antibodies

Emerging SARS-CoV-2 strains, B.1.1.7 and B.1.351, from the UK and South Africa, respectively show decreased neutralization by monoclonal antibodies and convalescent or vaccinee sera raised against the original wild-type virus, and are thus of clinical concern. However, the neutralization potency of two antibodies, 1-57 and 2-7, which target the receptor-binding domain (RBD) of spike, was unaffected by these emerging strains. Here, we report cryo-EM structures of 1-57 and 2-7 in complex with spike, revealing each of these antibodies to utilize a distinct mechanism to bypass or accommodate RBD mutations. Notably, each antibody represented a response with recognition distinct from those of frequent antibody classes. Moreover, many epitope residues recognized by 1-57 and 2-7 were outside hotspots of evolutionary pressure for both ACE2 binding and neutralizing antibody escape. We suggest the therapeutic use of antibodies like 1-57 and 2-7, which target less prevalent epitopes, could ameliorate issues of monoclonal antibody escape.

A Novel SARS-CoV-2 Variant of Concern, B.1.526, Identified in New York

Recent months have seen surges of SARS-CoV-2 infection across the globe with considerable viral evolution1-3. Extensive mutations in the spike protein may threaten efficacy of vaccines and therapeutic monoclonal antibodies4. Two signature mutations of concern are E484K, which plays a crucial role in the loss of neutralizing activity of antibodies, and N501Y, a driver of rapid worldwide transmission of the B.1.1.7 lineage. Here, we report the emergence of variant lineage B.1.526 that contains E484K and its alarming rise to dominance in New York City in early 2021. This variant is partially or completely resistant to two therapeutic monoclonal antibodies in clinical use and less susceptible to neutralization by convalescent plasma or vaccinee sera, posing a modest antigenic challenge. The B.1.526 lineage has now been reported from all 50 states in the US and numerous other countries. B.1.526 rapidly replaced earlier lineages in New York upon its emergence, with an estimated transmission advantage of 35%. Such transmission dynamics, together with the relative antibody resistance of its E484K sub-lineage, likely contributed to the sharp rise and rapid spread of B.1.526. Although SARS-CoV-2 B.1.526 initially outpaced B.1.1.7 in the region, its growth subsequently slowed concurrent with the rise of B.1.1.7 and ensuing variants.

Increased Resistance of SARS-CoV-2 Variants B.1.351 and B.1.1.7 to Antibody Neutralization

The COVID-19 pandemic has ravaged the globe, and its causative agent, SARS-CoV-2, continues to rage. Prospects of ending this pandemic rest on the development of effective interventions. Single and combination monoclonal antibody (mAb) therapeutics have received emergency use authorization1-3, with more in the pipeline4-7. Furthermore, multiple vaccine constructs have shown promise8, including two with ~95% protective efficacy against COVID-199,10. However, these interventions were directed toward the initial SARS-CoV-2 that emerged in 2019. The recent emergence of new SARS-CoV-2 variants B.1.1.7 in the UK11 and B.1.351 in South Africa12 is of concern because of their purported ease of transmission and extensive mutations in the spike protein. We now report that B.1.1.7 is refractory to neutralization by most mAbs to the N-terminal domain (NTD) of spike and relatively resistant to a few mAbs to the receptor-binding domain (RBD). It is not more resistant to convalescent plasma or vaccinee sera. Findings on B.1.351 are more worrisome in that this variant is not only refractory to neutralization by most NTD mAbs but also by multiple individual mAbs to the receptor-binding motif on RBD, largely due to an E484K mutation. Moreover, B.1.351 is markedly more resistant to neutralization by convalescent plasma (9.4 fold) and vaccinee sera (10.3-12.4 fold). B.1.351 and emergent variants13,14 with similar spike mutations present new challenges for mAb therapy and threaten the protective efficacy of current vaccines.

Potent SARS-CoV-2 Neutralizing Antibodies Directed Against Spike N-Terminal Domain Target a Single Supersite

Numerous antibodies that neutralize SARS-CoV-2 have been identified, and these generally target either the receptor-binding domain (RBD) or the N-terminal domain (NTD) of the viral spike. While RBD-directed antibodies have been extensively studied, far less is known about NTD-directed antibodies. Here we report cryo-EM and crystal structures for seven potent NTD-directed neutralizing antibodies in complex with spike or isolated NTD. These structures defined several antibody classes, with at least one observed in multiple convalescent donors. The structures revealed all seven antibodies to target a common surface, bordered by glycans N17, N74, N122, and N149. This site - formed primarily by a mobile {beta}-hairpin and several flexible loops - was highly electropositive, located at the periphery of the spike, and the largest glycan-free surface of NTD facing away from the viral membrane. Thus, in contrast to neutralizing RBD-directed antibodies that recognize multiple non-overlapping epitopes, potent NTD-directed neutralizing antibodies target a single supersite.

Modular basis for potent SARS-CoV-2 neutralization by a prevalent VH1-2-derived antibody class

Antibodies with heavy chains that derive from the VH1-2 gene constitute some of the most potent SARS-CoV-2-neutralizing antibodies yet identified. To provide insight into whether these genetic similarities inform common modes of recognition, we determined structures of the SARS-CoV-2 spike in complex with three VH1-2-derived antibodies: 2-15, 2-43, and H4. All three utilized VH1-2-encoded motifs to recognize the receptor-binding domain (RBD), with heavy chain N53I enhancing binding and light chain tyrosines recognizing F486RBD. Despite these similarities, class members bound both RBD-up and -down conformations of the spike, with a subset of antibodies utilizing elongated CDRH3s to recognize glycan N343 on a neighboring RBD - a quaternary interaction accommodated by an increase in RBD separation of up to 12 [A]. The VH1-2-antibody class thus utilizes modular recognition encoded by modular genetic elements to effect potent neutralization, with VH-gene component specifying recognition of RBD and CDRH3 component specifying quaternary interactions. HighlightsO_LIDetermine structures of VH1-2-derived antibodies 2-43, 2-15, and H4 in complex with SARS-CoV-2 spike C_LIO_LIDefine a multi-donor VH1-2-antibody class with modular components for RBD and quaternary recognition C_LIO_LIReveal structural basis of RBD-up and RBD-down recognition within the class C_LIO_LIShow somatic hypermutations and avidity to be critical for potency C_LIO_LIDelineate changes in spike conformation induced by CDRH3-mediated quaternary recognition C_LI