Conformational dynamics of SARS-CoV-2 trimeric spike glycoprotein in complex with receptor ACE2 revealed by cryo-EM

The recent outbreaks of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and its rapid international spread pose a global health emergency. The trimeric spike (S) glycoprotein interacts with its receptor human ACE2 to mediate viral entry into host-cells. Here we present cryo-EM structures of an uncharacterized tightly closed SARS-CoV-2 S-trimer and the ACE2-bound-S-trimer at 2.7-Å and 3.8-Å-resolution, respectively. The tightly closed S-trimer with inactivated fusion peptide may represent the ground prefusion state. ACE2 binding to the up receptor-binding domain (RBD) within S-trimer triggers continuous swing-motions of ACE2-RBD, resulting in conformational dynamics of S1 subunits. Noteworthy, SARS-CoV-2 S-trimer appears much more sensitive to ACE2-receptor than SARS-CoV S-trimer in terms of receptor-triggered transformation from the closed prefusion state to the fusion-prone open state, potentially contributing to the superior infectivity of SARS-CoV-2. We defined the RBD T470-T478 loop and residue Y505 as viral determinants for specific recognition of SARS-CoV-2 RBD by ACE2, and provided structural basis of the spike D614G-mutation induced enhanced infectivity. Our findings offer a thorough picture on the mechanism of ACE2-induced conformational transitions of S-trimer from ground prefusion state towards postfusion state, thereby providing important information for development of vaccines and therapeutics aimed to block receptor binding.Competing Interest StatementThe authors have declared no competing interest.View Full Text

The levels and significance of inflammasomes in the mouse retina following optic nerve crush.

Inflammasomes play an important role in neuroinflammation. However, their function during the secondary death of retinal cells after traumatic optic neuropathy and their dependence on pathogen stimuli remains unclear. Therefore, we evaluated the expression profiles of 10 different inflammasome-related mRNAs in the retina following an optic nerve crush (OPC) injury under both conventional sterile as well as non-sterile conditions, and validated two significantly varied ones on a protein level. While most factors were much more highly elevated in non-sterile conditions, both Nlrp1b and Nlrp3 inflammasome mRNAs were increased significantly on postoperative day 1 to day 7 in the mouse sterile OPC injury model. While production of the inflammation-associated cytokines IL-1ß and IL-18 could be continuously detected on an mRNA level postoperatively, a clear peak could be seen on day 7 that coincided with maximal expression of caspase-1 mRNA and with observation of retinal ganglion cells death, despite the mice being held in specific-pathogen free conditions. As such, the pro-inflammatory cytokines activated by inflammasome activation during OPC injury may drive secondary cell death through pyroptosis, and inhibition of these delayed responses may be an important means of preventing worsened injury and loss of vision in trauma patients.

Comparison of clinical effects between bromfenac sodium versus loteprednol etabonate following FS-LASIK / 中华实验眼科杂志

Objective To compare the efficacy,safety and tolerability between bromfenac sodium ophthalmic solution 0.1％ eye drop and loteprednol etabonate 0.5％ eye drop after femtosecond laser in situ keratomileusis (FS-LASIK).Methods A prospective randomized controlled trail was performed.Seventy-six patients who had been undergone FS-LASIK in Daping Hospital were enrolled from December 2013 to December 2014.They were divided into two groups randomly by using the random number table method.The bromfenac sodium group included 38 patients administered 0.1％ bromfenac sodium ophthalmic solution,and the loteprednol etabonate group comprised 38 patients treated with 0.5％ loteprednol etabonate.Patients in both groups initially administered tobramycin-dexamethasone four times a day after FS-LASIK for 1 week.Then the patients in the bromfenac sodium group were treated with bromfenac sodium twice a day until 1 month postoperatively.While the patients from the loteprednol etabonate group were treated with loteprednol etabonate twice a day until 1 month after surgery.Visual acuity,refraction,intraocular pressure and ocular manifestation were examined preoperative and 1 day,1 week,1 month,3 months,6 months after FS-LASIK.This study was approved by the medical ethics Committee of Daping Hospital.Results No significant difference was found in the rate of uncorrected visual acuity (UCVA) which achieved to preoperative best corrected visual acuity (BCVA) between the two groups at each time point after operation (x2 =8.000,P =0.613).There was no difference in spherical equivalent (SE) between the two groups postoperatively (Fgroup =1.137,P =0.288),but a significant difference was found between the different time points (Ftime =29.771,P =0.000).Postoperative SE in the two groups tended to have mild hyperopia in the early days,and then gradually tended to " zero" or mild myopia.There was a significant difference with intraocular pressure among different time points (Ftime =87.519,P =0.000),but no significant difference of intraocular pressure was found between the groups (Fgroup =1.989,P =0.161).One month after surgery,the intraocular pressure were higher than 20 mmHg in two eyes in the loteprednol etabonate group,and two eyes were 5 mmHg higher than preoperative intraocular pressure.In bromfenac group,no one was higher than 5 mmHg compared with the preoperative intraocular pressure,and the pressures of all the eyes were lower than 18 mmHg.All the patients in bromfenac group were no drug withdrawal.But three patients were forced to guide drug withdrawal due to high intraocular pressure in loteprednol group.Conclusions Bromfenac sodium is safe,effective and well tolerated after FS-LASIK.

Corvis measurement of intraocular pressure and its relationship with corneal biomechanical properties / 中华实验眼科杂志

Background Corneal biomechanical properties is important in the safety assessment of corneal refractive surgery.Corvis is a new device for measuring corneal biomechanics properties.Objective This study was to observe the correlation among corneal thickness, Corvis intraocular pressure and corneal biomechanical properties with Corvis.Methods A prospective observational study was performed.One hundred and fifty eyes of 75 patients with corneal thickness from 501 μm to 590 μm were divided into three groups according to the corneal thickness:low corneal thickness group (corneal thickness range from 501 μm to 530 μm), middle corneal thickness group (corneal thickness range from 531 μm to 560 μm) ,and high corneal thickness group (corneal thickness range from 561 μm to 590 μm);and 50 eyes of 25 patients for each group.The difference of intraocular pressure, corneal thickness and deformation amplitude (DA) among the three groups were analyzed by one-way ANOVA and the correlation among the groups were analyzed by liner regression.Results The DA in the low corneal thickness group and middle corneal thickness group were significantly higher than that in the high corneal thickness group (P ＜ 0.05).The intraocular pressure was statistically different among the 3 groups (F =9.98, P＜0.05).DA was negatively correlated with intraocular pressure and corneal thickness (r=-0.84,-0.33;both at P＜0.01), with the linear regression DA =1.69-0.04×IOP (F=366.19, t=-19.14,P＜0.01).Conclusions Corneal thickness cannot simply represent the corneal biomechanical properties in the safety assessment of corneal refractive surgery,IOP should be considered.