RESUMEN
The SARS-CoV-2 Omicron BA.1 variant emerged in late 2021 and is characterised by multiple spike mutations across all spike domains. Here we show that Omicron BA.1 has higher affinity for ACE2 compared to Delta, and confers very significant evasion of therapeutic monoclonal and vaccine-elicited polyclonal neutralising antibodies after two doses. mRNA vaccination as a third vaccine dose rescues and broadens neutralisation. Importantly, antiviral drugs remdesevir and molnupiravir retain efficacy against Omicron BA.1. We found that in human nasal epithelial 3D cultures replication was similar for both Omicron and Delta. However, in lower airway organoids, Calu-3 lung cells and gut adenocarcinoma cell lines live Omicron virus demonstrated significantly lower replication in comparison to Delta. We noted that despite presence of mutations predicted to favour spike S1/S2 cleavage, the spike protein is less efficiently cleaved in live Omicron virions compared to Delta virions. We mapped the replication differences between the variants to entry efficiency using spike pseudotyped virus (PV) entry assays. The defect for Omicron PV in specific cell types correlated with higher cellular RNA expression of TMPRSS2, and accordingly knock down of TMPRSS2 impacted Delta entry to a greater extent as compared to Omicron. Furthermore, drug inhibitors targeting specific entry pathways demonstrated that the Omicron spike inefficiently utilises the cellular protease TMPRSS2 that mediates cell entry via plasma membrane fusion. Instead, we demonstrate that Omicron spike has greater dependency on cell entry via the endocytic pathway requiring the activity of endosomal cathepsins to cleave spike. Consistent with suboptimal S1/S2 cleavage and inability to utilise TMPRSS2, syncytium formation by the Omicron spike was dramatically impaired compared to the Delta spike. Overall, Omicron appears to have gained significant evasion from neutralising antibodies whilst maintaining sensitivity to antiviral drugs targeting the polymerase. Omicron has shifted cellular tropism away from TMPRSS2 expressing cells that are enriched in cells found in the lower respiratory and GI tracts, with implications for altered pathogenesis.
RESUMEN
The SARS-CoV-2 B.1.617.2 (Delta) variant was first identified in the state of Maharashtra in late 2020 and spread throughout India, outcompeting pre-existing lineages including B.1.617.1 (Kappa) and B.1.1.7 (Alpha). In vitro, B.1.617.2 is 6-fold less sensitive to serum neutralising antibodies from recovered individuals, and 8-fold less sensitive to vaccine-elicited antibodies as compared to wild type Wuhan-1 bearing D614G. Serum neutralising titres against B.1.617.2 were lower in ChAdOx-1 versus BNT162b2 vaccinees. B.1.617.2 spike pseudotyped viruses exhibited compromised sensitivity to monoclonal antibodies against the receptor binding domain (RBD) and N-terminal domain (NTD), in particular to the clinically approved bamlavinimab and imdevimab monoclonal antibodies. B.1.617.2 demonstrated higher replication efficiency in both airway organoid and human airway epithelial systems as compared to B.1.1.7, associated with B.1.617.2 spike being in a predominantly cleaved state compared to B.1.1.7. Additionally we observed that B.1.617.2 had higher replication and spike mediated entry as compared to B.1.617.1, potentially explaining B.1.617.2 dominance. In an analysis of over 130 SARS-CoV-2 infected healthcare workers across three centres in India during a period of mixed lineage circulation, we observed substantially reduced ChAdOx-1 vaccine efficacy against B.1.617.2 relative to non-B.1.617.2. Compromised vaccine efficacy against the highly fit and immune evasive B.1.617.2 Delta variant warrants continued infection control measures in the post-vaccination era.
RESUMEN
The basolateral amygdala (BLA) plays a critical role in mediating physiological responses to emotional stress. Recent data suggest that angiotensin-(1-7) [Ang-(1-7)] can act centrally attenuating the cardiovascular response to acute stress. We investigated whether Ang-(1-7) in the BLA plays a role in the cardiovascular response to emotional stress. Under anesthesia, guide cannulas were implanted into the BLA of Wistar rats. Five days later, the femoral artery was cannulated for mean arterial pressure (MAP) and heart rate (HR) recordings. Microinjections of Ang-(1-7) (5 or 50 pmol), the Mas receptor antagonist A-779 (100 pmol), Ang-(1-7)+A-779 (50 + 100 pmol, respectively), or vehicle (NaCl 0.9%, control) were performed after 24h and rats were then submitted to stress trials. Injection of Ang-(1-7) into the BLA blocked the tachycardia (ΔHR: vehicle 135 ± 23 vs. Ang-(1-7) 9 ± 12 bpm; P<0.05) and the pressor response (ΔMAP: vehicle 28 ± 3 mmHg vs. Ang-(1-7) 6 ± 2 mmHg; P<0.05) produced by air jet stress. These effects were completely reversed by A-779 (ΔHR: 109 ± 11 bpm; ΔMAP: 18 ± 2 mmHg). Ang-(1-7) into the BLA also attenuated the pressor response evoked by cage-switch stress paradigm. These findings indicate that Ang-(1-7) can act in the BLA through the Mas receptors modulating the cardiovascular response evoked by emotional stress.
