ABSTRACT
The infection of the novel coronavirus SARS-CoV-2 have caused more than 150,000 deaths, but no vaccine or specific therapeutic antibody is currently available. SARS-CoV-2 relies on its spike protein, in particular the receptor binding domain (RBD), to bind human cell receptor angiotensin-converting enzyme 2 (ACE2) for viral entry, and thus targeting RBD holds the promise for preventing SARS-CoV-2 infection. In this work, a competitive biopanning strategy of a phage display antibody library was applied to screen blocking antibodies against RBD. High-affinity antibodies were enriched after the first round using a standard panning process in which RBD-His recombinant protein was immobilized as a bait. At the next two rounds, immobilized ACE2-Fc and free RBD-His proteins were mixed with the enriched phage antibodies. Antibodies binding to RBD at epitopes different from ACE2-binding site were captured by the immobilized ACE2-Fc, forming a "sandwich" complex. Only antibodies competed with ACE2 for recognizing RBD at the same or similar epitopes can bind to the free RBD-His in the supernatant and be subsequently separated by the Ni-NTA magnetic beads. Top 1 lead from the competitive biopanning of a synthetic antibody library, Lib AB1, was produced as the full-length IgG1 format. It was proved to competitively block the binding of RBD to ACE2 protein, and potently inhibit SARS-CoV-2 pseudovirus infection of ACE2-overexpressing Hela cells with IC50 values of 12nM. Nevertheless, top 1 lead from the standard biopanning of Lib AB1, can only bind to RBD in vitro but not have the blocking or neutralization activity. Our strategy can efficiently isolate the blocking antibodies of RBD, and it would speed up the discovery of neutralizing antibodies against SARS-CoV-2.
ABSTRACT
Objective To observe the effect of 15°-head up tilt position on quality of respiratory system during anesthesia recovery period in obese patients.Methods Eighty obese patients in ASA physical status Ⅰ or Ⅱ,aged 18-60 years,with BMI≥28 kg/m2,scheduled for elective otological surgery with microscopy,were randomly divided into 2 equal groups (n =40 each):the 15°-head up tilt position group (group H) and the supine position group (group C).With traditional induction,an esthesia was maintained by TCI of propofol 2-4 μg/ml and remifentanil 5-6ug/ml,not supplying muscle relaxant during operation.After operation,group H was in 15°-head up tilt position,while group C in supine position.The time spans from recovery of spontaneous breathing to meeting the extubation standard (X) and to meeting the standard for discharging form PACU (Y) were recorded.After extubation,we also recorded the time for SpO2decreased from 100％ to 92％ with fresh air (Z) and for SpO2 increased from 92％ to 100％ with pure oxygen (W).PaO2,PaCO2 and pH were monitored before oxygen inhalation,after 3 min of oxygen inhalation,at the end of surgery,before extubation and before discharging from PACU.Results Compared with group C [(19±6) min,(57±10) min,(51 ±9) s],the time of X (14±7) min,Y (45±7) min and W (39±11) s,was significantly shorter and the time of W was obviously longer in group H(P＜0.05).Compared with group C [(169.1± 29.4) mm Hg,(70.8±4.1) mm Hg],the PaO2was increased obviously before extubation and discharging from PACU in group H [(193.4±30.5) mm Hg,(82.2±3.4) mm Hg](P＜0.05).There was no significantly difference in PaO2 at other time points.There was no significantly difference in PaCO2and pH at all points.Conclusion 15°-head up tilt position during anesthesia recovery period in obese patients can effectively improve the quality of respiratory system.
