ABSTRACT
Understanding the mechanism of neutralizing antibodies (NAbs) against SARS-CoV-2 is critical for effective vaccines and therapeutics development. We recently reported an exceptionally potent NAb, BD-368-2, and revealed the existence of VH3-53/VH3-66 convergent NAbs in COVID-19. Here we report the 3.5-[A] cryo-EM structure of BD-368-2s Fabs in complex with a mutation-induced prefusion-state-stabilized spike trimer. Unlike VH3-53/VH3-66 NAbs, BD-368-2 fully blocks ACE2 binding by occupying all three receptor-binding domains (RBDs) simultaneously, regardless of their "up" and "down" positions. BD-368-2 also triggers fusogenic-like structural rearrangements of the spike trimer, which could impede viral entry. Moreover, BD-368-2 completely avoids the common epitope of VH3-53/VH3-66 NAbs, evidenced by multiple crystal structures of their Fabs in tripartite complexes with RBD, suggesting a new way of pairing potent NAbs to prevent neutralization escape. Together, these results rationalize a unique epitope that leads to exceptional neutralization potency, and provide guidance for NAb therapeutics and vaccine designs against SARS-CoV-2.
ABSTRACT
ObjectiveTo investigate the protective effect of sevoflurane postconditioning (Sevo-Postcon)on the hearts isolated from rats with diabetes mellitus (DM) of different duration against ischemia-reperfusion (I/R)injury.MethodsSeventy-two pathogen-free male SD rats weighing 200-240 g were randomly divided into 3 groups ( n =24 each):group Ⅰ rats without DM (C) ; group Ⅱ rats with 2 week DM (2w DM) and group Ⅲ rats with 6 week DM (6w DM).DM was produced by intraperitoneal (IP) 1％ streptozocin (STZ) 60 mg/kg and confirmed by fasting blood glucose concentration ＞ 16.7 mmol/L in groups Ⅱ and Ⅲ.Hearts were isolated from rats and perfused with Krebs-Henseleit buffer (KHB) in a Langendorff apparatus.After a 15 min stabilization period,the isolated hearts were subjected to 30 min of global no-flow ischemia followed by 75 min of reperfusion.Twelve hearts in each group were perfused after ischemia with KHB saturated with 3％ Sevo for 15 min followed by perfusion with regular KHB for 60 min.LVEDP,LVDP, ± dp/dt and HR were measured and recorded after 15 min stabilization (T0,baseline) and at 15 and 75 min of reperfusion (T1,2 ).Myocardial specimens were obtained at 15 min of reperfusion (T1) for detection of p-Akt expression (by Western blot analysis).Infarct size was determined at 75 min of reperfusion (T2).ResultsSevo-Postcon significantly improved cardiac function,reduced infarct size and up-regulated p-Akt expression in groups Ⅰ (C) and Ⅱ (2w DM),while in group Ⅲ (6w DM) Sevo-Postcon did not cause any change in cardiac function,infarct size and p-Akt expression as compared with the isolated hearts without Sevo-Postcon.ConclusionThe cardioprotective effect of Sevo-Postcon can be attenuated with increasing duration of DM by impairing PI3K/Akt signaling pathway.
